merging with main mujoco repo

2024-04-02 16:39:04 -04:00
parent 67a9f91c00 d7f131e086
commit a4b5355f46
136 changed files with 48702 additions and 2845 deletions
@@ -2129,12 +2129,6 @@ from its default.
   When this flag is enabled, :ref:`mj_inverse` will  interpret ``qacc`` as having been computed from the difference of
   two sequential velocities, and undo the above modification.
 .. _option-flag-sensornoise:
 :at:`sensornoise`: :at-val:`[disable, enable], "disable"`
   This flag enables the simulation of sensor noise. When disabled (which is the default) noise is not added to
   sensordata, even if the sensors specify non-zero noise amplitudes. When enabled, zero-mean Gaussian noise is added to
   the underlying deterministic sensor data. Its standard deviation is determined by the noise parameter of each sensor.
 .. _option-flag-multiccd:
@@ -2354,24 +2348,6 @@ rotations as unit quaternions.
   joint inertia in the model reference configuration. Note that the format is the same as the solref parameter of the
   constraint solver.
 .. _body-joint-limited:
 :at:`limited`: :at-val:`[false, true, auto], "auto"`
   This attribute specifies if the joint has limits. It interacts with the range attribute below. If this attribute
   is "false", joint limits are disabled. If this attribute is "true", joint limits are enabled. If this
   attribute is "auto", and :at:`autolimits` is set in :ref:`compiler <compiler>`, joint limits will be enabled
   if range is defined.
 .. _body-joint-actuatorfrclimited:
 :at:`actuatorfrclimited`: :at-val:`[false, true, auto], "auto"`
   This attribute specifies whether actuator forces acting on the joint should be clamped. See :ref:`CForceRange` for
   details. It is available only for scalar joints (hinge and slider) and ignored for ball and free joints. |br| This
   attribute interacts with the actuatorfrcrange attribute below. If this attribute is "false", actuator force
   clamping is disabled. If it is "true", actuator force clamping is enabled. If this attribute is "auto", and
   :at:`autolimits` is set in :ref:`compiler <compiler>`, actuator force clamping will be enabled if actuatorfrcrange
   is defined.
 .. _body-joint-solreflimit:
 .. _body-joint-solimplimit:
@@ -2400,16 +2376,44 @@ rotations as unit quaternions.
   joints, the limit is imposed on the angle of rotation (relative to the reference configuration) regardless of the
   axis of rotation. Only the second range parameter is used for ball joints; the first range parameter should be set to
   0. See the :ref:`Limit <coLimit>` section in the Computation chapter for more information.
-   |br| Setting this attribute without specifying :at:`limited` is an error, unless :at:`autolimits` is set in
+   |br| Setting this attribute without specifying :at:`limited` is an error if :at:`autolimits` is "false" in
   :ref:`compiler <compiler>`.
 .. _body-joint-limited:
 :at:`limited`: :at-val:`[false, true, auto], "auto"`
   This attribute specifies if the joint has limits. It interacts with the range attribute below. If this attribute
   is "false", joint limits are disabled. If this attribute is "true", joint limits are enabled. If this
   attribute is "auto", and :at:`autolimits` is set in :ref:`compiler <compiler>`, joint limits will be enabled
   if range is defined.
 .. _body-joint-actuatorfrcrange:
 :at:`actuatorfrcrange`: :at-val:`real(2), "0 0"`
   Range for clamping total actuator forces acting on this joint. See :ref:`CForceRange` for details. It is available
   only for scalar joints (hinge and slider) and ignored for ball and free joints. |br| The compiler expects the first
   value to be smaller than the second value. |br| Setting this attribute without specifying :at:`actuatorfrclimited`
-   is an error, unless :at:`compiler-autolimits` is set.
+   is an error if :at:`compiler-autolimits` is "false".
 .. _body-joint-actuatorfrclimited:
 :at:`actuatorfrclimited`: :at-val:`[false, true, auto], "auto"`
   This attribute specifies whether actuator forces acting on the joint should be clamped. See :ref:`CForceRange` for
   details. It is available only for scalar joints (hinge and slider) and ignored for ball and free joints. |br| This
   attribute interacts with the actuatorfrcrange attribute below. If this attribute is "false", actuator force
   clamping is disabled. If it is "true", actuator force clamping is enabled. If this attribute is "auto", and
   :at:`autolimits` is set in :ref:`compiler <compiler>`, actuator force clamping will be enabled if
   :at:`actuatorfrcrange` is defined.
 .. _body-joint-actuatorgravcomp:
 :at:`actuatorgravcomp`: :at-val:`[false, true], "false"`
   If this flag is enabled, gravity compensation applied to this joint is added to actuator forces
   (``mjData.qfrc_actuator``) rather than passive forces (``mjData.qfrc_passive``). Notionally, this means that gravity
   compensation is the result of a control system rather than natural buoyancy. In practice, enabling this flag is
   useful when joint-level actuator force clamping is used. In this case, the total actuation force applied on a joint,
   including gravity compensation, is guaranteed to not exceeed the specified limits. See :ref:`CForceRange` and
   :ref:`actuatorfrcrange<body-joint-actuatorfrcrange>` for more details on this type of force limit.
 .. _body-joint-margin:
@@ -3808,8 +3812,12 @@ saving the XML:
   in MuJoCo can be used as a rigid geom attached to a single body. In contrast, the flex generated here corresponds to
   a soft mesh with the same initial shape, where each vertex is a separate moving body (unless pinned).
-   **gmsh** is similar to mesh, but it loads a `GMSH file <https://gmsh.info//doc/texinfo/gmsh.html#MSH-file-format>`__
+   .. _gmsh-file-docs:
-   in format 4.1 (ascii or binary). The file extension can be anything; the parser recognizes the format by examining
+
   **gmsh** is similar to mesh, but it loads a GMSH file in
   `format 4.1 <https://gmsh.info//doc/texinfo/gmsh.html#MSH-file-format>`__
   and `format 2.2 <https://gmsh.info//doc/texinfo/gmsh.html#MSH-file-format-version-2-_0028Legacy_0029>`__
   (ascii or binary). The file extension can be anything; the parser recognizes the format by examining
   the file header. This is a very rich file format, allowing all kinds of elements with different dimensionality and
   topology. MuJoCo only supports GMSH element types 1, 2, 4 which happen to correspond to our 1D, 2D and 3D flexes and
   assumes that the nodes are specified in a single block. Only the Nodes and Elements sections of the GMHS file are
@@ -3817,7 +3825,7 @@ saving the XML:
   GMSH file contains meshes that are not supported by MuJoCo. :at:`dim` is automatically set to the dimensionality
   specified in the GMSH file. Presently this is the only mechanism to load a large tetrahedral mesh in MuJoCo and
   generate a corresponding soft entity. If such a mesh is available in a different file format, use the freely
-   available `GMSH software <https://gmsh.info/>`__ to convert it to GMSH 4.1.
+   available `GMSH software <https://gmsh.info/>`__ to convert it to GMSH in one of the supported versions.
   **direct** allows the user to specify the point and element data of the flexcomp directly in the XML. Note that
   flexcomp will still generate moving bodies automatically, as well as automate other settings; so it still provides
@@ -3873,7 +3881,7 @@ saving the XML:
 :at:`file`: :at-val:`string, optional`
   The name of the file from which a **mesh** or a **gmsh** is loaded. For mesh, the file extentsion is used to
   determine the file format. Supported formats are the same as in :ref:`mesh assets<asset-mesh>`. For gmsh, the file is
-   expected to be in GMSH format 4.1, ascii or binary.
+   expected to be in GMSH format 4.1 or 2.2, ascii or binary, see :ref:`here<gmsh-file-docs>`.
 .. _body-flexcomp-rigid:
@@ -5092,14 +5100,14 @@ specify them independently.
 :at:`ctrlrange`: :at-val:`real(2), "0 0"`
   Range for clamping the control input. The first value must be smaller than the second value.
-   |br| Setting this attribute without specifying :at:`ctrllimited` is an error, unless :at:`autolimits` is set in
+   |br| Setting this attribute without specifying :at:`ctrllimited` is an error if :at:`autolimits` is "false" in
   :ref:`compiler <compiler>`.
 .. _actuator-general-forcerange:
 :at:`forcerange`: :at-val:`real(2), "0 0"`
   Range for clamping the force output. The first value must be no greater than the second value.
-   |br| Setting this attribute without specifying :at:`forcelimited` is an error, unless :at:`autolimits` is set in
+   |br| Setting this attribute without specifying :at:`forcelimited` is an error if :at:`autolimits` is "false" in
   :ref:`compiler <compiler>`.
 .. _actuator-general-actrange:
@@ -5107,7 +5115,7 @@ specify them independently.
 :at:`actrange`: :at-val:`real(2), "0 0"`
   Range for clamping the activation state. The first value must be no greater than the second value.
   See the :ref:`Activation clamping <CActRange>` section for more details.
-   |br| Setting this attribute without specifying :at:`actlimited` is an error, unless :at:`autolimits` is set in
+   |br| Setting this attribute without specifying :at:`actlimited` is an error if :at:`autolimits` is "false" in
   :ref:`compiler <compiler>`.
 .. _actuator-general-lengthrange:
@@ -6485,10 +6493,12 @@ arms determined by the transmission). This sensor can be attached to any actuato
 :el-prefix:`sensor/` |-| **jointactuatorfrc** (*)
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-This element creates an actuator force sensor, measured at a joint. The quantity being sensed is the
+This element creates an actuator force sensor, measured at a joint. The quantity being sensed is the generalized force
-generalized force contributed by all actuators to a single scalar joint (hinge or slider). This type of sensor is
+contributed by all actuators to a single scalar joint (hinge or slider). If the joint's
-important when multiple actuators act on a single joint or when a single actuator act on multiple joints. See
+:ref:`actuatorgravcomp<body-joint-actuatorgravcomp>` attribute is "true", this sensor will also measure contributions by
-:ref:`CForceRange` for details.
+gravity compensation forces (which are added directly to the joint and would *not* register in the
 :ref:`actuatorfrc<sensor-actuatorfrc>`) sensor. This type of sensor is important when multiple actuators act on a single
 joint or when a single actuator act on multiple joints. See :ref:`CForceRange` for details.
 .. _sensor-jointactuatorfrc-name:
@@ -7382,6 +7392,8 @@ if omitted.
 .. _default-joint-actuatorfrclimited:
 .. _default-joint-actuatorgravcomp:
 .. _default-joint-solreflimit:
 .. _default-joint-solimplimit:
@@ -247,9 +247,9 @@
 |                                    |    |    +-----------------------------------------------------------------+-----------------------------------------------------------------+-----------------------------------------------------------------+-----------------------------------------------------------------+ |
 |                                    |    |    | :ref:`sensor<option-flag-sensor>`                               | :ref:`midphase<option-flag-midphase>`                           | :ref:`eulerdamp<option-flag-eulerdamp>`                         | :ref:`override<option-flag-override>`                           | |
 |                                    |    |    +-----------------------------------------------------------------+-----------------------------------------------------------------+-----------------------------------------------------------------+-----------------------------------------------------------------+ |
-|                                    |    |    | :ref:`energy<option-flag-energy>`                               | :ref:`fwdinv<option-flag-fwdinv>`                               | :ref:`invdiscrete<option-flag-invdiscrete>`                     | :ref:`sensornoise<option-flag-sensornoise>`                     | |
+|                                    |    |    | :ref:`energy<option-flag-energy>`                               | :ref:`fwdinv<option-flag-fwdinv>`                               | :ref:`invdiscrete<option-flag-invdiscrete>`                     | :ref:`multiccd<option-flag-multiccd>`                           | |
 |                                    |    |    +-----------------------------------------------------------------+-----------------------------------------------------------------+-----------------------------------------------------------------+-----------------------------------------------------------------+ |
-|                                    |    |    | :ref:`multiccd<option-flag-multiccd>`                           | :ref:`island<option-flag-island>`                               |                                                                 |                                                                 | |
+|                                    |    |    | :ref:`island<option-flag-island>`                               |                                                                 |                                                                 |                                                                 | |
 |                                    |    |    +-----------------------------------------------------------------+-----------------------------------------------------------------+-----------------------------------------------------------------+-----------------------------------------------------------------+ |
 +------------------------------------+----+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
 | mujoco |br| |L|                    |    | .. table::                                                                                                                                                                                                                                                                   |
@@ -286,9 +286,9 @@
 |                                    |    |    +-----------------------------------------------------------------+-----------------------------------------------------------------+-----------------------------------------------------------------+-----------------------------------------------------------------+ |
 |                                    |    |    | :ref:`solimpfriction<body-joint-solimpfriction>`                | :ref:`stiffness<body-joint-stiffness>`                          | :ref:`range<body-joint-range>`                                  | :ref:`actuatorfrcrange<body-joint-actuatorfrcrange>`            | |
 |                                    |    |    +-----------------------------------------------------------------+-----------------------------------------------------------------+-----------------------------------------------------------------+-----------------------------------------------------------------+ |
-|                                    |    |    | :ref:`margin<body-joint-margin>`                                | :ref:`ref<body-joint-ref>`                                      | :ref:`springref<body-joint-springref>`                          | :ref:`armature<body-joint-armature>`                            | |
+|                                    |    |    | :ref:`actuatorgravcomp<body-joint-actuatorgravcomp>`            | :ref:`margin<body-joint-margin>`                                | :ref:`ref<body-joint-ref>`                                      | :ref:`springref<body-joint-springref>`                          | |
 |                                    |    |    +-----------------------------------------------------------------+-----------------------------------------------------------------+-----------------------------------------------------------------+-----------------------------------------------------------------+ |
-|                                    |    |    | :ref:`damping<body-joint-damping>`                              | :ref:`frictionloss<body-joint-frictionloss>`                    | :ref:`user<body-joint-user>`                                    |                                                                 | |
+|                                    |    |    | :ref:`armature<body-joint-armature>`                            | :ref:`damping<body-joint-damping>`                              | :ref:`frictionloss<body-joint-frictionloss>`                    | :ref:`user<body-joint-user>`                                    | |
 |                                    |    |    +-----------------------------------------------------------------+-----------------------------------------------------------------+-----------------------------------------------------------------+-----------------------------------------------------------------+ |
 +------------------------------------+----+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
 | |_| body |br| |_| |L|              |    | .. table::                                                                                                                                                                                                                                                                   |
@@ -1320,11 +1320,11 @@
 |                                    |    |    +-----------------------------------------------------------------+-----------------------------------------------------------------+-----------------------------------------------------------------+-----------------------------------------------------------------+ |
 |                                    |    |    | :ref:`solimplimit<default-joint-solimplimit>`                   | :ref:`solreffriction<default-joint-solreffriction>`             | :ref:`solimpfriction<default-joint-solimpfriction>`             | :ref:`stiffness<default-joint-stiffness>`                       | |
 |                                    |    |    +-----------------------------------------------------------------+-----------------------------------------------------------------+-----------------------------------------------------------------+-----------------------------------------------------------------+ |
-|                                    |    |    | :ref:`range<default-joint-range>`                               | :ref:`actuatorfrcrange<default-joint-actuatorfrcrange>`         | :ref:`margin<default-joint-margin>`                             | :ref:`ref<default-joint-ref>`                                   | |
+|                                    |    |    | :ref:`range<default-joint-range>`                               | :ref:`actuatorfrcrange<default-joint-actuatorfrcrange>`         | :ref:`actuatorgravcomp<default-joint-actuatorgravcomp>`         | :ref:`margin<default-joint-margin>`                             | |
 |                                    |    |    +-----------------------------------------------------------------+-----------------------------------------------------------------+-----------------------------------------------------------------+-----------------------------------------------------------------+ |
-|                                    |    |    | :ref:`springref<default-joint-springref>`                       | :ref:`armature<default-joint-armature>`                         | :ref:`damping<default-joint-damping>`                           | :ref:`frictionloss<default-joint-frictionloss>`                 | |
+|                                    |    |    | :ref:`ref<default-joint-ref>`                                   | :ref:`springref<default-joint-springref>`                       | :ref:`armature<default-joint-armature>`                         | :ref:`damping<default-joint-damping>`                           | |
 |                                    |    |    +-----------------------------------------------------------------+-----------------------------------------------------------------+-----------------------------------------------------------------+-----------------------------------------------------------------+ |
-|                                    |    |    | :ref:`user<default-joint-user>`                                 |                                                                 |                                                                 |                                                                 | |
+|                                    |    |    | :ref:`frictionloss<default-joint-frictionloss>`                 | :ref:`user<default-joint-user>`                                 |                                                                 |                                                                 | |
 |                                    |    |    +-----------------------------------------------------------------+-----------------------------------------------------------------+-----------------------------------------------------------------+-----------------------------------------------------------------+ |
 +------------------------------------+----+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
 | |_| default |br| |_| |L|           |    | .. table::                                                                                                                                                                                                                                                                   |
@@ -5,14 +5,62 @@ Changelog
 Upcoming version (not yet released)
 -----------------------------------
 General
 ^^^^^^^
 .. admonition:: Breaking API changes
   :class: attention
   1. Removed the ability to natively add noise to sensors. Note that the ``mjModel.sensor_noise`` field and
      :ref:`corresponding attribute<CSensor>` are kept and now function as a convenient location for the user to save
      standard-deviation information for their own use. This feature was removed because:
      - There was no mechanism to seed the randon noise generator.
      - It was not thread-safe, even if seeding would have been provided, sampling on multiple threads would lead to
        non-reproducible results.
      - This feature was seen as overreach by the engine. Adding noise should be the user's responsibility.
      - We are not aware of anyone who was actually using the feature.
      **Migration:** Add noise to sensor values yourself.
 2. Added the :ref:`actuatorgravcomp<body-joint-actuatorgravcomp>` joint attribute. When enabled, gravity compensation
   forces on the joint are treated as applied by actuators. See attribute documentation for more details. The example
   model
   `refsite.xml <https://github.com/google-deepmind/mujoco/blob/main/test/engine/testdata/actuation/refsite.xml>`__,
   which demostrates Cartesian actuation of an arm, has been updated to use this attribute.
 3. Added support for gmsh format 2.2, as generated by e.g. `fTetwild <https://github.com/wildmeshing/fTetWild>`__.
 MJX
 ^^^
 4. Improved performance of SAT for convex collisions.
 5. Fixed bug for sphere/capsule-convex deep penetration.
 6. Fixed bug where ``mjx.Data`` produced by ``mjx.put_data`` had different treedef than ``mjx.make_data``.
 7. Throw an error for margin/gap for convex mesh collisions, since they are not supported.
 Simulate
 ^^^^^^^^
 8. Fixed bug in order of enable flag strings. Before this change, using the simulate UI to toggle the
   :ref:`invdiscrete<option-flag-invdiscrete>` or the (now removed) ``sensornoise`` flags would actually toggle the
   other flag.
 Python bindings
 ^^^^^^^^^^^^^^^
 .. youtube:: xHDS0n5DpqM
   :align: right
   :width: 240px
 9. Added the ``mujoco.minimize`` Python module for nonlinear least-squares, designed for System Identification (sysID).
   The sysID tutorial is work in progress, but a pedagogical colab notebook with examples, including Inverse
   Kinematics, is available here: |ls_colab|
   |br| The video on the right shows example clips from the tutorial.
 .. |ls_colab| image:: https://colab.research.google.com/assets/colab-badge.svg
              :target: https://colab.research.google.com/github/google-deepmind/mujoco/blob/main/python/least_squares.ipynb
 1. Improved performance of SAT for convex collisions.
 2. Fixed bug for sphere/capsule-convex deep penetration.
 Version 3.1.3 (March 5th, 2024)
-----------------------------------
+-------------------------------
 General
 ^^^^^^^
@@ -31,7 +79,6 @@ General
 MJX
 ^^^
 4. Improved performance of getting and putting device data.
   - Use ``tobytes()`` for numpy array serialization, which is orders of magnitude faster than converting to tuples.
@@ -50,16 +97,9 @@ Python bindings
 ^^^^^^^^^^^^^^^
 11. Fixed incorrect data types in the bindings for the ``geom``, ``vert``, ``elem``, and ``flex`` array members
    of the ``mjContact`` struct, and all array members of the ``mjrContext`` struct.
 12. Added the ``mujoco.minimize`` Python module for nonlinear least-squares, designed for System Identification (sysID).
    The sysID tutorial is work in progress, but a pedagogical colab notebook with examples, including Inverse
    Kinematics, is available here: |ls_colab|
 .. |ls_colab| image:: https://colab.research.google.com/assets/colab-badge.svg
              :target: https://colab.research.google.com/github/google-deepmind/mujoco/blob/main/python/least_squares.ipynb
 Version 3.1.2 (February 05, 2024)
-----------------------------------
+---------------------------------
 General
 ^^^^^^^
@@ -85,8 +85,7 @@ Ellipsoid model
   :figwidth: 50%
   :align: right
-   The flight-capable Drosophila Melanogaster model in this figure will be described in a
+   The flight-capable Drosophila Melanogaster model in this figure is described in :cite:t:`Vaxenburg2024`.
   forthcoming publication.
 In this section we describe and derive a stateless model of the forces exerted onto a moving rigid body by the
@@ -94,7 +93,6 @@ surrounding fluid, based on an ellipsoidal approximation of geom shape. This mod
 different types of fluid forces than the inertia-based model of the previous section. The motivating use-case for this
 model is insect flight, see figure on the right.
 Summary
 ~~~~~~~
@@ -426,7 +424,7 @@ increasing Reynolds numbers, and a single reference area :math:`A_D` may not be
 drag for highly irregular or slender bodies. For example, experimental fits are derived from problems ranging from
 falling playing cards :cite:p:`wang2004,andersen2005a,andersen2005b` to particle transport :cite:p:`loth2008,
 bagheri2016`. See screen capture of the
-`cards.xml <https://github.com/deepmind/mujoco/blob/main/model/card/cards.xml>`__ model on the right.
+`cards.xml <https://github.com/deepmind/mujoco/blob/main/model/cards/cards.xml>`__ model on the right.
 We derive a formula for :math:`\mathbf{f}_\text{D}` based on two surfaces :math:`A^\text{proj}_\mathbf{v}` and
 :math:`A_\text{max}`. The first, :math:`A^\text{proj}_\mathbf{v}`, is the cylindrical projection of the body onto a
@@ -426,12 +426,11 @@ typedef enum mjtEnableBit_ {      // enable optional feature bitflags
  mjENBL_ENERGY       = 1<<1,     // energy computation
  mjENBL_FWDINV       = 1<<2,     // record solver statistics
  mjENBL_INVDISCRETE  = 1<<3,     // discrete-time inverse dynamics
  mjENBL_SENSORNOISE  = 1<<4,     // add noise to sensor data
                                  // experimental features:
-  mjENBL_MULTICCD     = 1<<5,     // multi-point convex collision detection
+  mjENBL_MULTICCD     = 1<<4,     // multi-point convex collision detection
-  mjENBL_ISLAND       = 1<<6,     // constraint island discovery
+  mjENBL_ISLAND       = 1<<5,     // constraint island discovery
-  mjNENABLE           = 7         // number of enable flags
+  mjNENABLE           = 6         // number of enable flags
 } mjtEnableBit;
 typedef enum mjtJoint_ {          // type of degree of freedom
  mjJNT_FREE          = 0,        // global position and orientation (quat)       (7)
@@ -926,9 +925,9 @@ struct mjModel_ {
  int nemax;                      // number of potential equality-constraint rows
  int njmax;                      // number of available rows in constraint Jacobian
  int nconmax;                    // number of potential contacts in contact list
-  int nuserdata;                  // number of extra fields in mjData
+  int nuserdata;                  // number of mjtNums reserved for the user
-  int nsensordata;                // number of fields in sensor data vector
+  int nsensordata;                // number of mjtNums in sensor data vector
-  int npluginstate;               // number of fields in plugin state vector
+  int npluginstate;               // number of mjtNums in plugin state vector
  size_t narena;                  // number of bytes in the mjData arena (inclusive of stack)
  size_t nbuffer;                 // number of bytes in buffer
@@ -993,6 +992,7 @@ struct mjModel_ {
  int*      jnt_group;            // group for visibility                     (njnt x 1)
  mjtByte*  jnt_limited;          // does joint have limits                   (njnt x 1)
  mjtByte*  jnt_actfrclimited;    // does joint have actuator force limits    (njnt x 1)
  mjtByte*  jnt_actgravcomp;      // is gravcomp force applied via actuators  (njnt x 1)
  mjtNum*   jnt_solref;           // constraint solver reference: limit       (njnt x mjNREF)
  mjtNum*   jnt_solimp;           // constraint solver impedance: limit       (njnt x mjNIMP)
  mjtNum*   jnt_pos;              // local anchor position                    (njnt x 3)
@@ -215,6 +215,14 @@ The following features are **in development** and coming soon:
   * - Category
     - Feature
   * - :ref:`Geom <mjtGeom>`
     - ``SDF``, ``HFIELD``, ``ELLIPSOID``, ``CYLINDER``
   * - :ref:`Condim <coContact>`
     - 1, 4, 6
   * - :ref:`Constraint <mjtConstraint>`
     - :ref:`Frictionloss <coFriction>`, ``CONTACT_FRICTIONLESS``, ``CONTACT_ELLIPTIC``, ``FRICTION_DOF``
   * - :ref:`Integrator <mjtIntegrator>`
     - ``IMPLICIT``, ``IMPLICITFAST``
   * - Dynamics
     - :ref:`Inverse <mj_inverse>`
   * - :ref:`Transmission <mjtTrn>`
@@ -227,16 +235,8 @@ The following features are **in development** and coming soon:
     - ``MUSCLE``
   * - :ref:`Tendon Wrapping <mjtWrap>`
     - ``NONE``, ``JOINT``, ``PULLEY``, ``SITE``, ``SPHERE``, ``CYLINDER``
   * - :ref:`Geom <mjtGeom>`
     - ``HFIELD``, ``ELLIPSOID``, ``CYLINDER``
   * - :ref:`Constraint <mjtConstraint>`
     - :ref:`Frictionloss <coFriction>`, ``CONTACT_FRICTIONLESS``, ``CONTACT_ELLIPTIC``, ``FRICTION_DOF``
   * - :ref:`Integrator <mjtIntegrator>`
     - ``IMPLICIT``, ``IMPLICITFAST``
   * - :ref:`Cone <mjtCone>`
     - ``ELLIPTIC``
   * - :ref:`Condim <coContact>`
     - 1, 4, 6
   * - Fluid Model
     - :ref:`flEllipsoid`
   * - :ref:`Tendons <tendon>`
@@ -258,6 +258,8 @@ The following features are **unsupported**:
   * - Category
     - Feature
   * - :ref:`margin<body-geom-margin>` and :ref:`gap<body-geom-gap>`
     - Unimplemented for collisions with ``Mesh`` :ref:`Geom <mjtGeom>`.
   * - :ref:`Transmission <mjtTrn>`
     - ``TRN_JOINTINPARENT``, ``TRN_SLIDERCRANK``, ``TRN_BODY``
   * - :ref:`Actuator Dynamics <mjtDyn>`
@@ -270,8 +272,6 @@ The following features are **unsupported**:
     - ``PGS``
   * - :ref:`Sensors <mjtSensor>`
     - ``PLUGIN``, ``USER``
   * - :ref:`Geom <mjtGeom>`
     - ``SDF``
 .. _MjxSharpBits:
@@ -299,8 +299,9 @@ Collisions between large meshes
  SAT works well for smaller meshes but suffers in both runtime and memory for larger meshes.
  For
-  collisions with convex meshes, the convex decompositon of the mesh should have
+  collisions with convex meshes and primitives, the convex decompositon of the mesh should have
-  roughly **200 vertices or less** for reasonable performance.
+  roughly **200 vertices or less** for reasonable performance. For convex-convex collisions,
  the convex mesh should have roughly **fewer than 32 vertices**.
  With careful
  tuning, MJX can simulate scenes with mesh collisions -- see the MJX
  `shadow hand <https://github.com/google-deepmind/mujoco/tree/main/mjx/mujoco/mjx/benchmark/model/shadow_hand>`__
@@ -421,7 +421,7 @@ and the damping ratio is ignored. Equivalently, in the direct format, the :math:
   impedance is constant, then the penetration depth at rest is
   .. math::
-      r = \au \cdot (1 - d) \cdot \text{stiffness}
+      r = \frac{\au (1 - d)}{\text{stiffness}}
 .. tip::
   In the positive-value default format, the :math:`\text{timeconst}` parameter controls constraint **softness**.
@@ -431,6 +431,9 @@ and the damping ratio is ignored. Equivalently, in the direct format, the :math:
   The negative-value "direct" format is more flexible, for example allowing for perfectly elastic collisions
   (:math:`\text{damping} = 0`). It is the recommended format for system identification.
   A :math:`\text{dampratio}` of 1 in the positive-value format is equivalent to
   :math:`\text{damping} = 2 \sqrt{ \text{stiffness} }` in the direct format.
 .. _CContact:
 Contact parameters
@@ -1057,9 +1060,10 @@ Here we describe the XML attributes common to all sensor types, so as to avoid r
 :at:`name`: :at-val:`string, optional`
   Name of the sensor.
 :at:`noise`: :at-val:`real, "0"`
-   The standard deviation of zero-mean Gaussian noise added to the sensor output, when the :at:`sensornoise`
+   The standard deviation of the noise model of this sensor. In versions prior to 3.1.4, this would lead to noise being
-   attribute of :ref:`flag <option-flag>` is enabled. Sensor noise respects the sensor data type:
+   added to the sensors. In release 3.1.4 this feature was removed, see :doc:`3.1.4 changelog <changelog>` for a
-   quaternions and unit vectors remain normalized, non-negative quantities remain non-negative.
+   detailed justification. As of subsequent versions, this attrbute serves as a convenient location for saving standard
   deviation information for later use.
 :at:`cutoff`: :at-val:`real, "0"`
   When this value is positive, it limits the absolute value of the sensor output. It is also used to normalize the
   sensor output in the sensor data plots in :ref:`simulate.cc <saSimulate>`.
@@ -88,3 +88,14 @@
  year={2015},
  publisher={Nature Publishing Group}
 }
@article {Vaxenburg2024,
  author = {Roman Vaxenburg and Igor Siwanowicz and Josh Merel and Alice A Robie and Carmen Morrow and Guido Novati and Zinovia Stefanidi and Gwyneth M Card and Michael B Reiser and Matthew M Botvinick and Kristin M Branson and Yuval Tassa and Srinivas C Turaga},
  title = {Whole-body simulation of realistic fruit fly locomotion with deep reinforcement learning},
  elocation-id = {2024.03.11.584515},
  year = {2024},
  doi = {10.1101/2024.03.11.584515},
  publisher = {Cold Spring Harbor Laboratory},
  journal = {bioRxiv}
 }
@@ -74,12 +74,11 @@ typedef enum mjtEnableBit_ {      // enable optional feature bitflags
  mjENBL_ENERGY       = 1<<1,     // energy computation
  mjENBL_FWDINV       = 1<<2,     // record solver statistics
  mjENBL_INVDISCRETE  = 1<<3,     // discrete-time inverse dynamics
  mjENBL_SENSORNOISE  = 1<<4,     // add noise to sensor data
                                  // experimental features:
-  mjENBL_MULTICCD     = 1<<5,     // multi-point convex collision detection
+  mjENBL_MULTICCD     = 1<<4,     // multi-point convex collision detection
-  mjENBL_ISLAND       = 1<<6,     // constraint island discovery
+  mjENBL_ISLAND       = 1<<5,     // constraint island discovery
-  mjNENABLE           = 7         // number of enable flags
+  mjNENABLE           = 6         // number of enable flags
 } mjtEnableBit;
@@ -641,9 +640,9 @@ struct mjModel_ {
  int nemax;                      // number of potential equality-constraint rows
  int njmax;                      // number of available rows in constraint Jacobian
  int nconmax;                    // number of potential contacts in contact list
-  int nuserdata;                  // number of extra fields in mjData
+  int nuserdata;                  // number of mjtNums reserved for the user
-  int nsensordata;                // number of fields in sensor data vector
+  int nsensordata;                // number of mjtNums in sensor data vector
-  int npluginstate;               // number of fields in plugin state vector
+  int npluginstate;               // number of mjtNums in plugin state vector
  size_t narena;                  // number of bytes in the mjData arena (inclusive of stack)
  size_t nbuffer;                 // number of bytes in buffer
@@ -708,6 +707,7 @@ struct mjModel_ {
  int*      jnt_group;            // group for visibility                     (njnt x 1)
  mjtByte*  jnt_limited;          // does joint have limits                   (njnt x 1)
  mjtByte*  jnt_actfrclimited;    // does joint have actuator force limits    (njnt x 1)
  mjtByte*  jnt_actgravcomp;      // is gravcomp force applied via actuators  (njnt x 1)
  mjtNum*   jnt_solref;           // constraint solver reference: limit       (njnt x mjNREF)
  mjtNum*   jnt_solimp;           // constraint solver impedance: limit       (njnt x mjNIMP)
  mjtNum*   jnt_pos;              // local anchor position                    (njnt x 3)
@@ -215,6 +215,7 @@
    XMJV( int,     jnt_group,             njnt,          1                    ) \
    X   ( mjtByte, jnt_limited,           njnt,          1                    ) \
    X   ( mjtByte, jnt_actfrclimited,     njnt,          1                    ) \
    X   ( mjtByte, jnt_actgravcomp,       njnt,          1                    ) \
    X   ( mjtNum,  jnt_solref,            njnt,          mjNREF               ) \
    X   ( mjtNum,  jnt_solimp,            njnt,          mjNIMP               ) \
    X   ( mjtNum,  jnt_pos,               njnt,          3                    ) \
@@ -54,10 +54,9 @@ ENUMS: Mapping[str, EnumDecl] = dict([
             ('mjENBL_ENERGY', 2),
             ('mjENBL_FWDINV', 4),
             ('mjENBL_INVDISCRETE', 8),
-             ('mjENBL_SENSORNOISE', 16),
+             ('mjENBL_MULTICCD', 16),
-             ('mjENBL_MULTICCD', 32),
+             ('mjENBL_ISLAND', 32),
-             ('mjENBL_ISLAND', 64),
+             ('mjNENABLE', 6),
             ('mjNENABLE', 7),
         ]),
     )),
    ('mjtJoint',
@@ -42,10 +42,9 @@ class EnumsTest(absltest.TestCase):
                                          ('mjENBL_ENERGY', 1<<1),
                                          ('mjENBL_FWDINV', 1<<2),
                                          ('mjENBL_INVDISCRETE', 1<<3),
-                                          ('mjENBL_SENSORNOISE', 1<<4),
+                                          ('mjENBL_MULTICCD', 1<<4),
-                                          ('mjENBL_MULTICCD', 1<<5),
+                                          ('mjENBL_ISLAND', 1<<5),
-                                          ('mjENBL_ISLAND', 1<<6),
+                                          ('mjNENABLE', 6)))
                                          ('mjNENABLE', 7)))
  # values mostly increment by one with occasional overrides
  def test_mjtGeom(self):  # pylint: disable=invalid-name
@@ -1218,17 +1218,17 @@ STRUCTS: Mapping[str, StructDecl] = dict([
             StructFieldDecl(
                 name='nuserdata',
                 type=ValueType(name='int'),
-                 doc='number of extra fields in mjData',
+                 doc='number of mjtNums reserved for the user',
             ),
             StructFieldDecl(
                 name='nsensordata',
                 type=ValueType(name='int'),
-                 doc='number of fields in sensor data vector',
+                 doc='number of mjtNums in sensor data vector',
             ),
             StructFieldDecl(
                 name='npluginstate',
                 type=ValueType(name='int'),
-                 doc='number of fields in plugin state vector',
+                 doc='number of mjtNums in plugin state vector',
             ),
             StructFieldDecl(
                 name='narena',
@@ -1556,6 +1556,13 @@ STRUCTS: Mapping[str, StructDecl] = dict([
                 ),
                 doc='does joint have actuator force limits    (njnt x 1)',
             ),
             StructFieldDecl(
                 name='jnt_actgravcomp',
                 type=PointerType(
                     inner_type=ValueType(name='mjtByte'),
                 ),
                 doc='is gravcomp force applied via actuators  (njnt x 1)',
             ),
             StructFieldDecl(
                 name='jnt_solref',
                 type=PointerType(
@@ -16,6 +16,7 @@
 # pylint:disable=g-importing-member
 from mujoco.mjx._src.collision_driver import collision
 from mujoco.mjx._src.collision_driver import get_params
 from mujoco.mjx._src.collision_driver import ncon
 from mujoco.mjx._src.constraint import count_constraints
 from mujoco.mjx._src.constraint import make_constraint
@@ -48,4 +49,5 @@ from mujoco.mjx._src.solver import solve
 from mujoco.mjx._src.support import full_m
 from mujoco.mjx._src.support import is_sparse
 from mujoco.mjx._src.support import mul_m
 from mujoco.mjx._src.test_util import benchmark
 from mujoco.mjx._src.types import *
@@ -50,10 +50,10 @@ class GeomInfo(PyTreeNode):
  size: jax.Array
  face: Optional[jax.Array] = None
  vert: Optional[jax.Array] = None
-  edge: Optional[jax.Array] = None
+  edge_dir: Optional[jax.Array] = None
  facenorm: Optional[jax.Array] = None
-  face_edge: Optional[jax.Array] = None
+  edge: Optional[jax.Array] = None
-  face_edge_normal: Optional[jax.Array] = None
+  edge_face_normal: Optional[jax.Array] = None
 class SolverParams(PyTreeNode):
@@ -215,46 +215,47 @@ def sphere_convex(sphere: GeomInfo, convex: GeomInfo) -> Contact:
    return jp.dot(pos - faces[0], normal)
  support = get_support(faces, normals)
  has_separating_axis = jp.any(support >= 0)
-  # Pick the face with minimal penetration as long as it has support.
+  # Pick the face with the best separating axis.
  support = jp.where(support >= 0, -1e12, support)
  best_idx = support.argmax()
  face = faces[best_idx]
-  normal = normals[best_idx]
+  face_normal = normals[best_idx]
  # Get closest point between the polygon face and the sphere center point.
  # Project the sphere center point onto poly plane. If it's inside polygon
-  # edge normals, then we're done.
+  # side planes, then we're done.
-  pt = _project_pt_onto_plane(sphere_pos, face[0], normal)
+  pt = _project_pt_onto_plane(sphere_pos, face[0], face_normal)
  edge_p0 = jp.roll(face, 1, axis=0)
  edge_p1 = face
-  edge_normals = jax.vmap(jp.cross, in_axes=[0, None])(
+  side_normals = jax.vmap(jp.cross, in_axes=[0, None])(
      edge_p1 - edge_p0,
-      normal,
+      face_normal,
  )
  edge_dist = jax.vmap(
      lambda plane_pt, plane_norm: (pt - plane_pt).dot(plane_norm)
-  )(edge_p0, edge_normals)
+  )(edge_p0, side_normals)
-  inside = jp.all(edge_dist <= 0)  # lte to handle degenerate edges
+  pt_on_face = jp.all(edge_dist <= 0)  # lte to handle degenerate edges
-  # If the point is outside edge normals, project onto the closest edge plane
+  # If the point is outside side planes, project onto the closest side plane
  # that the point is in front of.
-  degenerate_edge = jp.all(edge_normals == 0, axis=1)
+  degenerate_edge = jp.all(side_normals == 0, axis=1)
  behind = edge_dist < 0.0
  edge_dist = jp.where(degenerate_edge | behind, 1e12, edge_dist)
  idx = edge_dist.argmin()
  edge_pt = math.closest_segment_point(edge_p0[idx], edge_p1[idx], pt)
-
+  pt = jp.where(pt_on_face, pt, edge_pt)
  pt = jp.where(inside, pt, edge_pt)
  # Get the normal, dist, and contact position.
-  n, d = math.normalize_with_norm(pt - sphere_pos)
+  pt_normal, d = math.normalize_with_norm(pt - sphere_pos)
  n = jp.where(inside | (d < 1e-6), normal, n)
  # Ensure normal points towards convex centroid.
-  n *= jp.where(jp.dot(pt, n) < 0, 1, -1)
+  inside = jp.dot(pt, pt_normal) > 0
  sign = jp.where(inside, -1, 1)
  n = jp.where(pt_on_face | (d < 1e-6), -face_normal, sign * pt_normal)
  d *= sign
  spt = sphere_pos + n * sphere.size[0]
-  dist = d - sphere.size[0]
+  dist = jp.where(has_separating_axis, 1.0, d - sphere.size[0])
  pos = (pt + spt) * 0.5
  # Go back to world frame.
@@ -292,8 +293,7 @@ def capsule_convex(cap: GeomInfo, convex: GeomInfo) -> Contact:
  support = get_support(faces, normals)
  has_support = jp.all(support < 0)
-  # Pick the face with minimal penetration as long as it has support.
+  # Pick the face with minimal penetration.
  support = jp.where(support >= 0, -1e12, support)
  best_idx = support.argmax()
  face = faces[best_idx]
  normal = normals[best_idx]
@@ -302,12 +302,12 @@ def capsule_convex(cap: GeomInfo, convex: GeomInfo) -> Contact:
  # the face.
  edge_p0 = jp.roll(face, 1, axis=0)
  edge_p1 = face
-  edge_normals = jax.vmap(jp.cross, in_axes=[0, None])(
+  side_planes = jax.vmap(jp.cross, in_axes=[0, None])(
      edge_p1 - edge_p0,
      normal,
  )
  cap_pts_clipped, mask = _clip_edge_to_planes(
-      cap_pts[0], cap_pts[1], edge_p0, edge_normals
+      cap_pts[0], cap_pts[1], edge_p0, side_planes
  )
  cap_pts_clipped = cap_pts_clipped - normal * cap.size[0]
  face_pts = jax.vmap(_project_pt_onto_plane, in_axes=[0, None, None])(
@@ -316,33 +316,65 @@ def capsule_convex(cap: GeomInfo, convex: GeomInfo) -> Contact:
  # Create variables for the face contact.
  pos = (cap_pts_clipped + face_pts) * 0.5
  contact_normal = -jp.stack([normal] * 2, 0)
-  penetration = jp.where(
+  face_penetration = jp.where(
      mask & has_support, jp.dot(face_pts - cap_pts_clipped, normal), -1
  )
-  # Get a potential edge contact.
+  # Pick a potential shallow edge contact.
-  edge_closest, cap_closest, t_a, t_b = jax.vmap(
+  def get_edge_axis(edge):
-      math.closest_segment_to_segment_points_w_barycentric,
+    edge_closest_pt, cap_closest_pt = math.closest_segment_to_segment_points(
-      in_axes=[0, 0, None, None],
+        edge[0], edge[1], cap_pts[0], cap_pts[1]
-  )(edge_p0, edge_p1, cap_pts[0], cap_pts[1])
+    )
-  e_idx = ((edge_closest - cap_closest) ** 2).sum(axis=1).argmin()
+    edge_dir = edge_closest_pt - cap_closest_pt
-  cap_closest_pt, edge_closest_pt = cap_closest[e_idx], edge_closest[e_idx]
+    degenerate_edge_dir = jp.sum(jp.square(edge_dir)) < 1e-6
-  edge_dist = math.norm(cap_closest_pt - edge_closest_pt)
+    edge_axis, edge_dist = math.normalize_with_norm(edge_dir)
-  t_a, t_b = t_a[e_idx], t_b[e_idx]
+    return (
-  in_segment = ((t_a > 0) & (t_a < 1)) | ((t_b > 0) & (t_b < 1))
+        edge_dist,
-  # Ensure edge_axis points towards the convex centroid.
+        edge_axis,
-  edge_axis = jp.cross(edge_p0[e_idx] - edge_p1[e_idx], axis)
+        degenerate_edge_dir,
-  sign = jp.where(jp.dot(edge_closest_pt, edge_axis) < 0, 1, -1)
+        edge_closest_pt,
-  edge_axis *= sign
+        cap_closest_pt,
-  degenerate_edge_axis = (edge_axis**2).sum() < 1e-6
+    )
-  edge_axis = math.normalize(edge_axis)
+
  edge = jp.take(convex.vert, convex.edge, axis=0)
  edge_face_normal = convex.edge_face_normal  # pytype: disable=attribute-error
  res = jax.vmap(get_edge_axis)(edge.reshape(-1, 2, 3))
  e_idx = jp.abs(res[0]).argmin()
  (
      edge_dist,
      edge_axis,
      degenerate_edge_dir,
      edge_closest_pt,
      cap_closest_pt,
  ) = jax.tree_map(lambda x, i=e_idx: jp.take(x, i, axis=0), res)
  edge_face_normals = edge_face_normal[e_idx]
  edge_voronoi_front = ((edge_face_normals @ edge_axis) < 0).all()
  shallow = ~degenerate_edge_dir & edge_voronoi_front
  edge_penetration = jp.where(shallow, cap.size[0] - edge_dist, -1)
  # Determine edge contact position.
  edge_pos = (
      edge_closest_pt + (cap_closest_pt + edge_axis * cap.size[0])
  ) * 0.5
-  edge_penetration = cap.size[0] - edge_dist
+  edge_dir_parallel_to_face = (
-  has_edge_contact = (edge_penetration > 0) & in_segment & ~degenerate_edge_axis
+      jp.abs(edge_axis.dot(normal)) > 0.99
  ) & ~degenerate_edge_dir
  min_face_penetration = face_penetration.min()
  has_edge_contact = (
      (edge_penetration > 0)
      # prefer edge contact if the edge is smaller than face penetration
      & jp.where(
          min_face_penetration > 0,
          edge_penetration < min_face_penetration,
          True,
      )
      # prefer face contact if the edge axis is parallel to the face normal
      & ~edge_dir_parallel_to_face
      # make sure we have a shallow contact
      & edge_voronoi_front
  )
  # Get the contact info.
  pos = jp.where(has_edge_contact, pos.at[0].set(edge_pos), pos)
@@ -355,7 +387,7 @@ def capsule_convex(cap: GeomInfo, convex: GeomInfo) -> Contact:
  n = n @ convex.mat.T
  dist = -jp.where(
-      has_edge_contact, penetration.at[0].set(edge_penetration), penetration
+      has_edge_contact, jp.array([edge_penetration, -1]), face_penetration
  )
  frame = jax.vmap(math.make_frame)(n)
  return dist, pos, frame
@@ -598,8 +630,9 @@ def _sat_bruteforce(
  We return both the edge and face contacts. Valid contacts can be checked with
  dist < 0. Resulting edge contacts should be preferred over face contacts.
-  This method checks all unique edge-pairs and is thus costly to run over large
+  This method checks all separating axes via a brute force support function, and
-  meshes, but is more performant for smaller meshes (boxes, tetrahedra, etc.).
+  is thus costly to run over large meshes, but is more performant for smaller
  meshes (boxes, tetrahedra, etc.).
  Args:
    faces_a: Faces for hull A.
@@ -699,7 +732,7 @@ def _arcs_intersect(
  return (cba * dba < 0) & (adc * bdc < 0) & (cba * bdc > 0)
-def _sat_approx(
+def _sat_gaussmap(
    centroid_a: jax.Array,
    faces_a: jax.Array,
    faces_b: jax.Array,
@@ -707,23 +740,16 @@ def _sat_approx(
    vertices_b: jax.Array,
    normals_a: jax.Array,
    normals_b: jax.Array,
-    face_edges_a: jax.Array,
+    edges_a: jax.Array,
-    face_edges_b: jax.Array,
+    edges_b: jax.Array,
-    face_edge_normals_a: jax.Array,
+    edge_face_normals_a: jax.Array,
-    face_edge_normals_b: jax.Array,
+    edge_face_normals_b: jax.Array,
 ) -> Tuple[jax.Array, jax.Array, jax.Array]:
  """Runs the Separating Axis Test for a pair of hulls.
-  Runs the separating axis test for all faces. After obtaining a reference
+  Runs the separating axis test for all faces. Tests edge separating axes via
-  and incident face, tests edge separating axes via edge intersections
+  edge intersections on gauss maps for all edge pairs. h/t to Dirk Gregorius
-  on gauss maps.
+  for the implementation details and gauss map trick.
  Certain meshes can have nearly parallel coplanar faces that are not merged.
  Thus reference/incident faces can be non-overlapping, and face contacts will
  not get generated. Since we only check edge separating axes on
  reference/incident faces, the correct edge separating axes may also be
  missing. We mitigate this issue by checking nearly coplanar anti-parallel
  reference/incident faces for support, hence why this method is "approximate".
  Args:
    centroid_a: Centroid of hull A.
@@ -733,10 +759,10 @@ def _sat_approx(
    vertices_b: Vertices for hull B.
    normals_a: Normal vectors for hull A faces.
    normals_b: Normal vectors for hull B faces.
-    face_edges_a: Edges for faces in hull A.
+    edges_a: Edges for hull A.
-    face_edges_b: Edges for faces in hull B.
+    edges_b: Edges for hull B.
-    face_edge_normals_a: Edge normals for faces in hull A.
+    edge_face_normals_a: Face normals for edges in hull A.
-    face_edge_normals_b: Edge normals for faces in hull B.
+    edge_face_normals_b: Face normals for edges in hull B.
  Returns:
    tuple of dist, pos, and normal
@@ -784,75 +810,61 @@ def _sat_approx(
      -best_axis,
  )
-  # Handle edge separating axes by checking edge pairs on the reference and
+  # Handle edge separating axes by checking all edge pairs.
-  # incident faces. In principle, the correct edge-edge separating axis can be
+  a_idx = jp.tile(jp.arange(edges_a.shape[0]), reps=edges_b.shape[0])
-  # created from edge pairs on the reference and incident faces.
+  b_idx = jp.repeat(
-  # first get the edge directions and face edge normals
+      jp.arange(edges_b.shape[0]), repeats=edges_a.shape[0], axis=0
-  face_edges_a = face_edges_a[face_a_idx]
+  )
-  v_norm = jax.vmap(math.normalize)
+  normal_a_1 = edge_face_normals_a[a_idx, 0]
-  face_edges_dir_a = v_norm(face_edges_a[:, 0] - face_edges_a[:, 1])
+  normal_a_2 = edge_face_normals_a[a_idx, 1]
-  face_edges_b = face_edges_b[face_b_idx]
+  normal_b_1 = edge_face_normals_b[b_idx, 0]
-  face_edges_dir_b = v_norm(face_edges_b[:, 0] - face_edges_b[:, 1])
+  normal_b_2 = edge_face_normals_b[b_idx, 1]
-  face_edge_normals_a = face_edge_normals_a[face_a_idx]
+  is_minkowski_face = jax.vmap(_arcs_intersect)(
-  face_edge_normals_b = face_edge_normals_b[face_b_idx]
+      normal_a_1, normal_a_2, -normal_b_1, -normal_b_2
  # scatter to all edge pairs
  edge_idx_a = jp.repeat(
      jp.arange(face_edges_a.shape[0]), face_edges_b.shape[0]
  )
  edge_idx_b = jp.tile(jp.arange(face_edges_b.shape[0]), face_edges_a.shape[0])
  face_edges_dir_a = face_edges_dir_a[edge_idx_a]
  face_edges_dir_b = face_edges_dir_b[edge_idx_b]
  face_edges_pt_a = face_edges_a[:, 0][edge_idx_a]
  face_edges_pt_b = face_edges_b[:, 0][edge_idx_b]
  face_edge_normals_a = face_edge_normals_a[edge_idx_a]
  face_edge_normals_b = face_edge_normals_b[edge_idx_b]
-  @jax.vmap
+  # get distances
  edge_a_dir = jax.vmap(math.normalize)(edges_a[:, 0] - edges_a[:, 1])[a_idx]
  edge_b_dir = jax.vmap(math.normalize)(edges_b[:, 0] - edges_b[:, 1])[b_idx]
  edges_a, edges_b = edges_a[a_idx], edges_b[b_idx]
  edge_a_pt, edge_a_pt_2 = edges_a[:, 0], edges_a[:, 1]
  edge_b_pt, edge_b_pt_2 = edges_b[:, 0], edges_b[:, 1]
  def get_normals(a_dir, a_pt, b_dir):
-    edge_axis = math.normalize(jp.cross(a_dir, b_dir))
+    edge_axis = jp.cross(a_dir, b_dir)
    degenerate_edge_axis = jp.sum(edge_axis**2) < 1e-6
    edge_axis = math.normalize(edge_axis)
    # correct normal to point from a to b, object b is at the origin
    sign = jp.where(jp.dot(edge_axis, a_pt - centroid_a) > 0.0, 1.0, -1.0)
-    return edge_axis * sign
+    return edge_axis * sign, degenerate_edge_axis
-  edge_axes = get_normals(face_edges_dir_a, face_edges_pt_a, face_edges_dir_b)
+  edge_axes, degenerate_edge_axes = jax.vmap(get_normals)(
-  edge_dist = jax.vmap(jp.dot)(edge_axes, face_edges_pt_b - face_edges_pt_a)
+      edge_a_dir, edge_a_pt, edge_b_dir)
-  # handle degenerate axes
+  edge_dist = jax.vmap(jp.dot)(edge_axes, edge_b_pt - edge_a_pt)
-  edge_dist = jp.where((edge_axes**2).sum(axis=1) < 1e-6, 1e6, edge_dist)
+  # handle degenerate axis
-  # ensure edges create a minkowski face by testing intersection on gauss maps
+  edge_dist = jp.where(degenerate_edge_axes, -jp.inf, edge_dist)
-  is_minkowski_face = jax.vmap(_arcs_intersect)(
+  # ensure edges create minkowski face
-      face_edge_normals_a[:, 0],
+  edge_dist = jp.where(is_minkowski_face, edge_dist, -jp.inf)
      face_edge_normals_a[:, 1],
      -face_edge_normals_b[:, 0],
      -face_edge_normals_b[:, 1],
  )
  edge_dist = jp.where(is_minkowski_face, edge_dist, 1e6)
  edge_dist = jp.where(edge_dist > 0, -1e6, edge_dist)
  best_edge_idx = edge_dist.argmax()
  best_edge_dist = edge_dist[best_edge_idx]
-  # prefer edge over face contacts as long as we have a valid edge contact
+  is_edge_contact = jp.where(
-  is_edge_contact = (best_edge_dist > dist.min() + 1e-6) & (best_edge_dist < 0)
+      dist.max() < 0, best_edge_dist > dist.max() - 1e-6,
-  normal = jp.where(is_edge_contact, edge_axes[best_edge_idx], normal)
+      (best_edge_dist < 0) & ~jp.isinf(best_edge_dist)
  dist = jp.where(is_edge_contact, jp.array([best_edge_dist, 1, 1, 1]), dist)
  # A failure mode occurs if faces are very narrow and nearly parallel
  # (i.e. faces did not get merged properly as coplanar faces). The face
  # contacts will be empty since the reference/incident faces may not overlap.
  # An edge-edge separating axis will not be found, since the reference and
  # incident faces will also not overlap or necessarily create a minkowski face.
  # Thus, we approximate the contact for anti-parallel faces with support.
  anti_parallel = incident_face_norm.dot(ref_face_norm) < -0.97
  dist = dist.at[0].set(
      jp.where(
          anti_parallel
          & ~is_face_separating
          & (dist > 0).all()
          & ~is_edge_contact,
          -support[best_idx],
          dist[0],
      )
  )
  is_edge_contact = is_edge_contact & ~is_face_separating
  normal = jp.where(is_edge_contact, edge_axes[best_edge_idx], normal)
  dist = jp.where(
      is_edge_contact,
      jp.array([best_edge_dist, 1, 1, 1]),
      dist,
  )
  a_closest, b_closest = math.closest_segment_to_segment_points(
      edge_a_pt[best_edge_idx], edge_a_pt_2[best_edge_idx],
      edge_b_pt[best_edge_idx], edge_b_pt_2[best_edge_idx])
  pos = jp.where(
      is_edge_contact,
      jp.tile(0.5 * (a_closest + b_closest), (4, 1)), pos)
  return dist, pos, normal
@@ -892,15 +904,15 @@ def convex_convex(c1: GeomInfo, c2: GeomInfo) -> Contact:
  unique_edges1 = jp.take(vertices1, c1.edge, axis=0)
  unique_edges2 = jp.take(vertices2, c2.edge, axis=0)
-  face_edges1 = jp.take(vertices1, c1.face_edge, axis=0)
+  edges1 = jp.take(vertices1, c1.edge, axis=0)
-  face_edges2 = jp.take(vertices2, c2.face_edge, axis=0)
+  edges2 = jp.take(vertices2, c2.edge, axis=0)
-  face_edge_normals1 = c1.face_edge_normal @ to_local_mat.T
+  edge_face_normals1 = c1.edge_face_normal @ to_local_mat.T
-  face_edge_normals2 = c2.face_edge_normal
+  edge_face_normals2 = c2.edge_face_normal
  enable_bruteforce = (
      unique_edges1.shape[0] * unique_edges2.shape[0]
-      < face_edges1[0].shape[0] * face_edges2[0].shape[0]
+      < edges1[0].shape[0] * edges2[0].shape[0]
  )
  if enable_bruteforce:
    dist, pos, normal = _sat_bruteforce(
@@ -914,7 +926,7 @@ def convex_convex(c1: GeomInfo, c2: GeomInfo) -> Contact:
        unique_edges2,
    )
  else:
-    dist, pos, normal = _sat_approx(
+    dist, pos, normal = _sat_gaussmap(
        to_local_pos,
        faces1,
        faces2,
@@ -922,10 +934,10 @@ def convex_convex(c1: GeomInfo, c2: GeomInfo) -> Contact:
        vertices2,
        normals1,
        normals2,
-        face_edges1,
+        edges1,
-        face_edges2,
+        edges2,
-        face_edge_normals1,
+        edge_face_normals1,
-        face_edge_normals2,
+        edge_face_normals2,
    )
  # Go back to world frame.
@@ -14,7 +14,7 @@
 # ==============================================================================
 """Collide geometries."""
-from typing import Callable, Dict, Optional, Sequence, Tuple, Union
+from typing import Callable, Dict, List, Optional, Sequence, Tuple, Union
 import jax
 from jax import numpy as jp
@@ -33,6 +33,7 @@ from mujoco.mjx._src.collision_convex import plane_convex
 from mujoco.mjx._src.collision_convex import sphere_convex
 from mujoco.mjx._src.collision_primitive import capsule_capsule
 from mujoco.mjx._src.collision_primitive import plane_capsule
 from mujoco.mjx._src.collision_primitive import plane_ellipsoid
 from mujoco.mjx._src.collision_primitive import plane_sphere
 from mujoco.mjx._src.collision_primitive import sphere_capsule
 from mujoco.mjx._src.collision_primitive import sphere_sphere
@@ -48,6 +49,7 @@ _COLLISION_FUNC = {
    (GeomType.PLANE, GeomType.SPHERE): plane_sphere,
    (GeomType.PLANE, GeomType.CAPSULE): plane_capsule,
    (GeomType.PLANE, GeomType.BOX): plane_convex,
    (GeomType.PLANE, GeomType.ELLIPSOID): plane_ellipsoid,
    (GeomType.PLANE, GeomType.MESH): plane_convex,
    (GeomType.SPHERE, GeomType.SPHERE): sphere_sphere,
    (GeomType.SPHERE, GeomType.CAPSULE): sphere_capsule,
@@ -187,6 +189,31 @@ def _dynamic_params(
  return SolverParams(friction, solref, solreffriction, solimp, margin, gap)
 def get_params(
    m: Union[Model, mujoco.MjModel], candidates: Sequence[Candidate]
 ) -> Tuple[List[int], List[int], SolverParams]:
  """Gets solver params for a list of collision candidates."""
  # group sol params by different candidate types
  typ_cands = {}
  for c in candidates:
    typ = (c.ipair > -1, c.geomp > -1)
    typ_cands.setdefault(typ, []).append(c)
  geom1, geom2, params = [], [], []
  for (pair, priority), candidates in typ_cands.items():
    geom1.extend([c.geom1 for c in candidates])
    geom2.extend([c.geom2 for c in candidates])
    if pair:
      params.append(_pair_params(m, candidates))
    elif priority:
      params.append(_priority_params(m, candidates))
    else:
      params.append(_dynamic_params(m, candidates))
  params = jax.tree_map(lambda *x: jp.concatenate(x), *params)
  return geom1, geom2, params
 def _pair_info(
    m: Model, d: Data, geom1: Sequence[int], geom2: Sequence[int]
 ) -> Tuple[GeomInfo, GeomInfo, Sequence[Dict[str, Optional[int]]]]:
@@ -205,20 +232,20 @@ def _pair_info(
      info = info.replace(
          face=jp.stack([m.geom_convex_face[i] for i in geom]),
          vert=jp.stack([m.geom_convex_vert[i] for i in geom]),
-          edge=jp.stack([m.geom_convex_edge_dir[i] for i in geom]),
+          edge_dir=jp.stack([m.geom_convex_edge_dir[i] for i in geom]),
          facenorm=jp.stack([m.geom_convex_facenormal[i] for i in geom]),
-          face_edge_normal=jp.stack(
+          edge=jp.stack([m.geom_convex_edge[i] for i in geom]),
-              [m.geom_convex_face_edge_normal[i] for i in geom]
+          edge_face_normal=jp.stack(
              [m.geom_convex_edge_face_normal[i] for i in geom]
          ),
          face_edge=jp.stack([m.geom_convex_face_edge[i] for i in geom]),
      )
      in_axes = in_axes.replace(
          face=0,
          vert=0,
-          edge=0,
+          edge_dir=0,
          facenorm=0,
-          face_edge=0,
+          edge=0,
-          face_edge_normal=0,
+          edge_face_normal=0,
      )
    return info, in_axes
@@ -276,24 +303,7 @@ def _collide_geoms(
  if not fn:
    return Contact.zero()
-  # group sol params by different candidate types
+  geom1, geom2, params = get_params(m, candidates)
  typ_cands = {}
  for c in candidates:
    typ = (c.ipair > -1, c.geomp > -1)
    typ_cands.setdefault(typ, []).append(c)
  geom1, geom2, params = [], [], []
  for (pair, priority), candidates in typ_cands.items():
    geom1.extend([c.geom1 for c in candidates])
    geom2.extend([c.geom2 for c in candidates])
    if pair:
      params.append(_pair_params(m, candidates))
    elif priority:
      params.append(_priority_params(m, candidates))
    else:
      params.append(_dynamic_params(m, candidates))
  params = jax.tree_map(lambda *x: jp.concatenate(x), *params)
  g1, g2, in_axes = _pair_info(m, d, geom1, geom2)
  # Run a crude version of broadphase.
@@ -132,37 +132,93 @@ class SphereCollisionTest(parameterized.TestCase):
    </mujoco>
  """
-  def test_sphere_convex(self):
+  def test_sphere_convex_face(self):
-    d, dx = _collide(self._SPHERE_CONVEX)
+    # no contact
    xml = self._SPHERE_CONVEX.replace(
        '<body pos="0.52 0 0.52">', '<body pos="0.55 0 0.5">'
    )
    d, dx = _collide(xml)
    self.assertEmpty(d.contact.dist)
    self.assertGreater(dx.contact.dist, 0)
    # face contact
    xml = self._SPHERE_CONVEX.replace(
        '<body pos="0.52 0 0.52">', '<body pos="0.51 0 0.25">'
    )
    d, dx = _collide(xml)
    for field in dataclasses.fields(Contact):
-      _assert_attr_eq(dx.contact, d.contact, field.name, 'sphere_convex', 1e-4)
+      _assert_attr_eq(dx.contact, d.contact, field.name, 'face', 1e-4)
-    # test deep penetration
+    # deep face contact
    xml = self._SPHERE_CONVEX.replace(
        '<body pos="0.52 0 0.52">', '<body pos="0.48 0 0.47">'
    )
    d, dx = _collide(xml)
    self.assertTrue((dx.contact.dist < 0).all())
    self.assertTrue((d.contact.dist < 0).all())
    np.testing.assert_allclose(dx.contact.dist, [-0.07], atol=1e-5)
    np.testing.assert_array_almost_equal(dx.contact.pos, d.contact.pos)
    np.testing.assert_array_almost_equal(
        dx.contact.frame, d.contact.frame.reshape((-1, 3, 3))
    )
  def test_sphere_convex_edge(self):
    # edge contact
    d, dx = _collide(self._SPHERE_CONVEX)
    for field in dataclasses.fields(Contact):
      _assert_attr_eq(dx.contact, d.contact, field.name, 'edge', 1e-4)
    # deep edge penetration
    xml = self._SPHERE_CONVEX.replace(
        '<body pos="0.52 0 0.52">', '<body pos="0.49 0 0.49">'
    )
    d, dx = _collide(xml)
    self.assertTrue((dx.contact.dist < 0).all())
    self.assertTrue((d.contact.dist < 0).all())
    np.testing.assert_allclose(dx.contact.dist, [-0.06], atol=1e-5)
    np.testing.assert_array_almost_equal(dx.contact.pos, d.contact.pos)
    np.testing.assert_array_almost_equal(
        dx.contact.frame, d.contact.frame.reshape((-1, 3, 3))
    )
-    # test sphere center on vertex
+    # vertex contact
    xml = self._SPHERE_CONVEX.replace(
        '<body pos="0.52 0 0.52">', '<body pos="0.5 0.52 0.51">'
    )
    d, dx = _collide(xml)
    for field in dataclasses.fields(Contact):
      _assert_attr_eq(dx.contact, d.contact, field.name, 'vertex', 1e-4)
    # sphere center on vertex
    xml = self._SPHERE_CONVEX.replace(
        '<body pos="0.52 0 0.52">', '<body pos="0.5 0 0.5">'
    )
    d, dx = _collide(xml)
    for field in dataclasses.fields(Contact):
      _assert_attr_eq(dx.contact, d.contact, field.name, 'vertex_center', 1e-4)
-    self.assertTrue((dx.contact.dist < 0).all())
+
-    self.assertTrue((d.contact.dist < 0).all())
+class EllipsoidCollisionTest(parameterized.TestCase):
-    np.testing.assert_array_almost_equal(dx.contact.pos, d.contact.pos)
+
-    np.testing.assert_array_almost_equal(
+  _ELLIPSOID_PLANE = """
-        dx.contact.frame, d.contact.frame.reshape((-1, 3, 3))
+    <mujoco>
-    )
+      <worldbody>
        <geom name="floor" size="0 0 .05" type="plane"/>
        <body pos="0 0 0.03" euler="45 0 0">
          <freejoint/>
          <geom size=".15 .03 .05" type="ellipsoid"/>
        </body>
      </worldbody>
    </mujoco>
  """
  def test_plane_ellipsoid(self):
    """Tests ellipsoid plane contact."""
    d, dx = _collide(self._ELLIPSOID_PLANE)
    self.assertLess(dx.contact.dist[0], 0)
    for field in dataclasses.fields(Contact):
      _assert_attr_eq(
          dx.contact, d.contact, field.name, 'ellipsoid-plane', 1e-5)
 class CapsuleCollisionTest(parameterized.TestCase):
@@ -248,8 +304,8 @@ class CapsuleCollisionTest(parameterized.TestCase):
    </mujoco>
  """
-  def test_capsule_convex(self):
+  def test_capsule_convex_face(self):
-    """Tests a capsule-convex collision for a face contact."""
+    """Tests face contact."""
    d, dx = _collide(self._CAP_BOX)
    # sort positions for comparison
@@ -263,7 +319,8 @@ class CapsuleCollisionTest(parameterized.TestCase):
    for field in dataclasses.fields(Contact):
      _assert_attr_eq(dx.contact, d.contact, field.name, 'capsule_convex', 1e-4)
-    # test deep face penetration
+  def test_capsule_convex_face_deep(self):
    """Tests deep face penetration."""
    xml = self._CAP_BOX.replace('<body pos="0 0 0.54">', '<body pos="0 0 0.4">')
    _, dx = _collide(xml)
@@ -294,7 +351,7 @@ class CapsuleCollisionTest(parameterized.TestCase):
  """
  def test_capsule_convex_edge(self):
-    """Tests a capsule-convex collision for an edge contact."""
+    """Tests edge contact."""
    d, dx = _collide(self._CAP_EDGE_BOX)
    c = dx.contact
@@ -305,17 +362,62 @@ class CapsuleCollisionTest(parameterized.TestCase):
    for field in dataclasses.fields(Contact):
      _assert_attr_eq(c, d.contact, field.name, 'capsule_convex_edge', 1e-4)
-    # test deep edge penetration
+  def test_capsule_convex_edge_deep(self):
    """Tests deep edge penetration."""
    xml = self._CAP_EDGE_BOX.replace(
-        '<body pos="0.5 0 0.55"', '<body pos="0.5 0 0.48"'
+        '<body pos="0.5 0 0.55"', '<body pos="0.5 0 0.42"'
    )
    _, dx = _collide(xml)
    np.testing.assert_array_equal(dx.contact.dist < 0, np.array([True, False]))
    np.testing.assert_array_almost_equal(dx.contact.dist[0], np.array([-0.13]))
    np.testing.assert_array_almost_equal(
-        dx.contact.pos[0], np.array([0.483, 0, 0.471]), decimal=3
+        dx.contact.pos[0], np.array([0.5, 0, 0.435]), decimal=3
    )
    np.testing.assert_array_almost_equal(
-        dx.contact.frame[0, 0], np.array([-0.5, 0, -0.866]), decimal=3
+        dx.contact.frame[0, 0], np.array([0, 0, -1]), decimal=3
    )
  def test_capsule_convex_edge_shallow_tip(self):
    """Tests shallow edge penetration on the tip of the capsule."""
    # the capsule sphere is inside the edge voronoi region, so there is an
    # edge contact
    xml = self._CAP_EDGE_BOX.replace(
        '<geom fromto="-0.6 0 0 0.6 0 0" size="0.05"',
        '<geom fromto="0.6 0 0.6 -0.05 0 0" size="0.1"',
    )
    xml = xml.replace('<body pos="0.5 0 0.55"', '<body pos="0.58 0 0.55"')
    d, dx = _collide(xml)
    c = dx.contact
    self.assertEqual(c.pos.shape[0], 2)
    self.assertGreater(c.dist[1], 0)
    # extract the contact point with penetration
    c = jax.tree_map(lambda x: jp.take(x, 0, axis=0)[None], dx.contact)
    for field in dataclasses.fields(Contact):
      _assert_attr_eq(c, d.contact, field.name, 'edge_shallow_tip1', 1e-4)
    np.testing.assert_array_almost_equal(
        dx.contact.frame[0][0, :3], np.array([-0.43952, 0.0, -0.898233])
    )
    # the capsule sphere is outside the edge voronoi region, so there is a
    # face contact
    xml = self._CAP_EDGE_BOX.replace(
        '<geom fromto="-0.6 0 0 0.6 0 0" size="0.05"',
        '<geom fromto="-0.6 0 0.6 -0.05 0 0" size="0.1"',
    )
    xml = xml.replace('<body pos="0.5 0 0.55"', '<body pos="0.5 0 0.52"')
    d, dx = _collide(xml)
    c = dx.contact
    self.assertEqual(c.pos.shape[0], 2)
    self.assertGreater(c.dist[1], 0)
    # extract the contact point with penetration
    c = jax.tree_map(lambda x: jp.take(x, 0, axis=0)[None], dx.contact)
    for field in dataclasses.fields(Contact):
      _assert_attr_eq(c, d.contact, field.name, 'edge_shallow_tip2', 1e-4)
    np.testing.assert_array_almost_equal(
        dx.contact.frame[0][0, :3], np.array([0.0, 0.0, -1.0])
    )
@@ -448,7 +550,7 @@ class ConvexTest(absltest.TestCase):
  """
  def test_convex_convex(self):
-    """Tests generic convex-convex collision via _sat_approx."""
+    """Tests generic convex-convex collision via _sat_gaussmap."""
    directory = epath.resource_path('mujoco.mjx')
    assets = {
        'meshes/dodecahedron.stl': (
@@ -463,6 +565,44 @@ class ConvexTest(absltest.TestCase):
    np.testing.assert_array_less(0, c.dist[1:])
    np.testing.assert_array_almost_equal(c.frame[0, 0], np.array([0, 0, 1]))
  _CONVEX_CONVEX_THIN = """
    <mujoco>
      <asset>
        <mesh name="poly"
         vertex="0.3 0 0  0 0.5 0  -0.3 0 0  0 -0.5 0  0 -1 1  0 1 1"
         face="0 1 5  0 5 4  0 4 3  3 4 2  2 4 5  1 2 5  0 2 1  0 3 2"/>
      </asset>
      <worldbody>
        <body pos="0.0 2.0 0.35" euler="0 0 90">
          <freejoint/>
          <geom size="0.2 0.2 0.2" type="mesh" mesh="poly"/>
        </body>
        <body pos="0.0 2.0 2.281" euler="180 0 0">
          <freejoint/>
          <geom size="0.2 0.2 0.2" type="mesh" mesh="poly"/>
        </body>
      </worldbody>
    </mujoco>
  """
  def test_convex_convex_edge(self):
    """Tests convex-convex collisions with edge contact via _sat_gaussmap."""
    _, dx = _collide(self._CONVEX_CONVEX_THIN)
    c = dx.contact
    # Only one contact point for an edge contact.
    self.assertLess(c.dist[0], 0)
    np.testing.assert_array_less(0, c.dist[1:])
    np.testing.assert_array_almost_equal(c.frame[0, 0], np.array([0, 0, 1]))
    np.testing.assert_array_almost_equal(
        c.pos[0], np.array([0, 2, 1.3155]), decimal=5)
    _, dx = _collide(
        self._CONVEX_CONVEX_THIN.replace(
            'pos="0.0 2.0 0.35"', 'pos="0.0 2.0 0"'))
    c = dx.contact
    self.assertTrue((c.dist > 0).all())
 class BodyPairFilterTest(absltest.TestCase):
  """Tests that certain body pairs get filtered."""
@@ -568,11 +708,11 @@ class NconTest(parameterized.TestCase):
        m.numeric_data[m.numeric_adr[i]] = -1
    ncon = collision_driver.ncon(m)
-    self.assertEqual(ncon, 307)
+    self.assertEqual(ncon, 98)
    mx = mjx.put_model(m)
    ncon = collision_driver.ncon(mx)
-    self.assertEqual(ncon, 307)
+    self.assertEqual(ncon, 98)
 class TopKContactTest(absltest.TestCase):
@@ -65,6 +65,19 @@ def plane_capsule(plane: GeomInfo, cap: GeomInfo) -> Contact:
  return jax.tree_map(lambda *x: jp.concatenate(x), *contacts)
 def plane_ellipsoid(plane: GeomInfo, ellipsoid: GeomInfo) -> Contact:
  """Calculates one contact between an ellipsoid and a plane."""
  n = plane.mat[:, 2]
  size = ellipsoid.size
  sphere_support = -math.normalize((ellipsoid.mat.T @ n) * size)
  pos = ellipsoid.pos + ellipsoid.mat @ (sphere_support * size)
  dist = jp.dot(n, pos - plane.pos)
  pos = pos - n * dist * 0.5
  return jax.tree_map(
      lambda x: jp.expand_dims(x, axis=0), (dist, pos, math.make_frame(n))
  )
 def _sphere_sphere(
    pos1: jax.Array, radius1: jax.Array, pos2: jax.Array, radius2: jax.Array
 ) -> Contact:
@@ -121,6 +134,7 @@ def capsule_capsule(cap1: GeomInfo, cap2: GeomInfo) -> Contact:
 # store ncon as function attributes
 plane_sphere.ncon = 1
 plane_capsule.ncon = 2
 plane_ellipsoid.ncon = 1
 sphere_sphere.ncon = 1
 sphere_capsule.ncon = 1
 capsule_capsule.ncon = 1
@@ -138,8 +138,7 @@ def _validate(m: mujoco.MjModel):
    raise NotImplementedError('Tendons are not supported.')
  # check collision geom types
-  candidate_set = collision_driver.collision_candidates(m)
+  for (g1, g2, *_), c in collision_driver.collision_candidates(m).items():
  for g1, g2, *_ in candidate_set:
    g1, g2 = mujoco.mjtGeom(g1), mujoco.mjtGeom(g2)
    if g1 == mujoco.mjtGeom.mjGEOM_PLANE and g2 in (
        mujoco.mjtGeom.mjGEOM_PLANE,
@@ -149,6 +148,12 @@ def _validate(m: mujoco.MjModel):
      continue
    if collision_driver.get_collision_fn((g1, g2)) is None:
      raise NotImplementedError(f'({g1}, {g2}) collisions not implemented.')
    *_, params = collision_driver.get_params(m, c)
    margin_gap = not np.allclose(np.concatenate([params.margin, params.gap]), 0)
    if mujoco.mjtGeom.mjGEOM_MESH in (g1, g2) and margin_gap:
      raise NotImplementedError(
          f'Margin and gap not implemented for ({g1}, {g2})'
      )
  # TODO(erikfrey): warn for high solver iterations, nefc, etc.
@@ -91,10 +91,16 @@ def put_model(m: mujoco.MjModel, device=None) -> types.Model:
    raise NotImplementedError('only condim=3 is supported')
  # check collision geom types
-  for g1, g2, *_ in collision_driver.collision_candidates(m):
+  for (g1, g2, *_), c in collision_driver.collision_candidates(m).items():
    g1, g2 = mujoco.mjtGeom(g1), mujoco.mjtGeom(g2)
    if collision_driver.get_collision_fn((g1, g2)) is None:
      g1, g2 = mujoco.mjtGeom(g1), mujoco.mjtGeom(g2)
      raise NotImplementedError(f'({g1}, {g2}) has no collision function')
    *_, params = collision_driver.get_params(m, c)
    margin_gap = not np.allclose(np.concatenate([params.margin, params.gap]), 0)
    if mujoco.mjtGeom.mjGEOM_MESH in (g1, g2) and margin_gap:
      raise NotImplementedError(
          f'Margin and gap not implemented for ({g1}, {g2})'
      )
  for enum_field, enum_type, mj_type in (
      (m.actuator_biastype, types.BiasType, mujoco.mjtBias),
@@ -172,7 +178,7 @@ def make_data(m: Union[types.Model, mujoco.MjModel]) -> types.Data:
      ctrl=zero_nu,
      qfrc_applied=zero_nv,
      xfrc_applied=zero_nbody_6,
-      eq_active=jp.zeros(m.neq, dtype=int),
+      eq_active=jp.zeros(m.neq, dtype=jp.uint8),
      qacc=zero_nv,
      act_dot=zero_na,
      xpos=zero_nbody_3,
@@ -233,6 +239,7 @@ def _get_contact(
  ncon = cx.dist.shape[0]
  c.efc_address[:] = np.arange(efc_start, efc_start + ncon * 4, 4)[con_id]
  c.dim[:] = 3
 def get_data(
@@ -374,6 +381,9 @@ def put_data(m: mujoco.MjModel, d: mujoco.MjData, device=None) -> types.Data:
  for fname in ('xmat', 'ximat', 'geom_xmat', 'site_xmat', 'cam_xmat'):
    fields[fname] = fields[fname].reshape((-1, 3, 3))
  # MJX does not support islanding, so only transfer the first solver_niter
  fields['solver_niter'] = fields['solver_niter'][0]
  # pad efc fields: MuJoCo efc arrays are sparse for inactive constraints.
  # efc_J is also optionally column-sparse (typically for large nv).  MJX is
  # neither: it contains zeros for inactive constraints, and efc_J is always
@@ -209,6 +209,25 @@ class ModelIOTest(parameterized.TestCase):
          </worldbody>
        </mujoco>"""))
  def test_margin_gap_mesh_not_implemented(self):
    with self.assertRaises(NotImplementedError):
      mjx.put_model(mujoco.MjModel.from_xml_string("""
        <mujoco>
          <asset>
            <mesh name="box" vertex="-1 -1 -1 1 -1 -1 1 1 -1 1 1 1 1 -1 1 -1 1 -1 -1 1 1 -1 -1 1" scale="1 1 1"/>
          </asset>
          <worldbody>
            <body>
              <freejoint/>
              <geom type="mesh" mesh="box" margin="0.3"/>
            </body>
            <body>
              <freejoint/>
              <geom size="0.05"/>
            </body>
          </worldbody>
        </mujoco>"""))
 class DataIOTest(parameterized.TestCase):
  """IO tests for mjx.Data."""
@@ -434,5 +453,20 @@ class DataIOTest(parameterized.TestCase):
    self.assertEqual(d_2.contact.frame.shape, (1, 9))
    np.testing.assert_allclose(d_2.contact.frame, d.contact.frame)
  def test_make_matches_put(self):
    """Test that make_data produces a pytree that matches put_data."""
    m = mujoco.MjModel.from_xml_string(_MULTIPLE_CONSTRAINTS)
    d = mujoco.MjData(m)
    mujoco.mj_step(m, d, 2)
    dx = mjx.put_data(m, d)
    step_fn = lambda d: d.replace(time=d.time + 1)
    step_fn_jit = jax.jit(step_fn).lower(dx).compile()
    # placing an MjData onto device should yield the same treedef mjx.Data as
    # calling make_data.  they should be interchangeable for jax functions:
    step_fn_jit(mjx.make_data(m))
 if __name__ == '__main__':
  absltest.main()
@@ -331,9 +331,9 @@ def closest_segment_point_and_dist(
  return closest, dist
-def closest_segment_to_segment_points_w_barycentric(
+def closest_segment_to_segment_points(
    a0: jax.Array, a1: jax.Array, b0: jax.Array, b1: jax.Array
-) -> Tuple[jax.Array, jax.Array, jax.Array, jax.Array]:
+) -> Tuple[jax.Array, jax.Array]:
  """Returns closest points between two line segments."""
  # Gets the closest segment points by first finding the closest points
  # between two lines. Points are then clipped to be on the line segments
@@ -364,10 +364,6 @@ def closest_segment_to_segment_points_w_barycentric(
  t_a = jp.clip(orig_t_a, -half_len_a, half_len_a)
  t_b = jp.clip(orig_t_b, -half_len_b, half_len_b)
  # reparametrize t_a, t_b
  t_a_01 = (orig_t_a + half_len_a) / jp.maximum(len_a, 1e-6)
  t_b_01 = (orig_t_b + half_len_b) / jp.maximum(len_b, 1e-6)
  best_a = a_mid + dir_a * t_a
  best_b = b_mid + dir_b * t_b
@@ -381,12 +377,4 @@ def closest_segment_to_segment_points_w_barycentric(
  best_a = jp.where(d1 < d2, new_a, best_a)
  best_b = jp.where(d1 < d2, best_b, new_b)
-  return best_a, best_b, t_a_01, t_b_01
+  return best_a, best_b
 def closest_segment_to_segment_points(
    a0: jax.Array, a1: jax.Array, b0: jax.Array, b1: jax.Array
 ) -> Tuple[jax.Array, jax.Array]:
  """Returns closest points between two line segments."""
  a, b, *_ = closest_segment_to_segment_points_w_barycentric(a0, a1, b0, b1)
  return a, b
@@ -49,8 +49,8 @@ _DERIVED_ARGS = [
    'geom_convex_vert',
    'geom_convex_edge_dir',
    'geom_convex_facenormal',
-    'geom_convex_face_edge',
+    'geom_convex_edge',
-    'geom_convex_face_edge_normal',
+    'geom_convex_edge_face_normal',
 ]
 DERIVED = {(Model, d) for d in _DERIVED_ARGS}
@@ -114,7 +114,7 @@ def _get_unique_edge_dir(vert: np.ndarray, face: np.ndarray) -> np.ndarray:
  return edges[unique_edge_idx]
-def _get_face_edge_normals(
+def _get_edge_normals(
    face: np.ndarray, face_norm: np.ndarray
 ) -> Tuple[np.ndarray, np.ndarray]:
  """Returns face edges and face edge normals."""
@@ -133,7 +133,7 @@ def _get_face_edge_normals(
      continue
    edge_map_list[tuple(face_edge_flat[i])].append(edge_face_norm[i])
-  edge_map = {}
+  edges, edge_face_normals = [], []
  for k, v in edge_map_list.items():
    v = np.array(v)
    if len(v) > 2:
@@ -145,19 +145,10 @@ def _get_face_edge_normals(
      # and face vertices were down sampled. In either case, we ignore these
      # edges.
      continue
-    edge_map[k] = v
+    edges.append(k)
    edge_face_normals.append(v)
-  # for each face, list the edge normals
+  return np.array(edges), np.array(edge_face_normals)
  face_edge_normal = []
  for face_idx in range(face_edge.shape[0]):
    normals = []
    for edge in face_edge[face_idx]:
      k = tuple(edge)
      normals.append(edge_map.get(k, np.zeros((2, 3))))
    face_edge_normal.append(np.array(normals))
  face_edge_normal = np.array(face_edge_normal)
  return face_edge, face_edge_normal
 def _convex_hull_2d(points: np.ndarray, normal: np.ndarray) -> np.ndarray:
@@ -297,15 +288,15 @@ def _geom_mesh_kwargs(
  vert = np.array(tm_convex.vertices)
  face = _merge_coplanar(tm_convex, mesh_info)
  facenormal = _get_face_norm(vert, face)
-  face_edge, face_edge_normal = _get_face_edge_normals(face, facenormal)
+  edge, edge_face_normal = _get_edge_normals(face, facenormal)
  return {
      'geom_convex_face': vert[face],
      'geom_convex_face_vert_idx': face,
      'geom_convex_vert': vert,
      'geom_convex_edge_dir': _get_unique_edge_dir(vert, face),
      'geom_convex_facenormal': facenormal,
-      'geom_convex_face_edge': face_edge,
+      'geom_convex_edge': edge,
-      'geom_convex_face_edge_normal': face_edge_normal,
+      'geom_convex_edge_face_normal': edge_face_normal,
  }
@@ -80,7 +80,7 @@ class GeomMeshKwargsTest(absltest.TestCase):
    self.assertEqual(h['geom_convex_facenormal'].shape, (5, 3))
    # face edges
-    edges = np.concatenate(h['geom_convex_face_edge'])
+    edges = h['geom_convex_edge']
    edges = np.vectorize(map_.get)(edges)
    mask = edges[:, 0] != edges[:, 1]
    edges = edges[mask]
@@ -92,27 +92,18 @@ class GeomMeshKwargsTest(absltest.TestCase):
        edges,
        np.array([
            [0, 2],
            [0, 2],
            [0, 3],
            [0, 3],
            [0, 4],
            [0, 4],
            [1, 2],
            [1, 2],
            [1, 3],
            [1, 3],
            [1, 4],
            [1, 4],
            [2, 4],
            [2, 4],
            [3, 4],
            [3, 4],
        ]),
    )
    # face edge normals
-    edge_normal = h['geom_convex_face_edge_normal']
+    edge_normal = h['geom_convex_edge_face_normal']
    edge_normal = np.concatenate(edge_normal)
    edge_normal = edge_normal[mask]
    edge_normal = np.take_along_axis(
        edge_normal, sort_col_idx[..., None], axis=1
@@ -120,8 +111,8 @@ class GeomMeshKwargsTest(absltest.TestCase):
    edge_normal = edge_normal[sort_row_idx]
    edge_normal_02 = np.array([[0.4472136, -0.0, 0.89442719], [-1.0, 0.0, 0.0]])
    np.testing.assert_array_almost_equal(
-        edge_normal[:2],
+        edge_normal[:1],
-        np.array([edge_normal_02, edge_normal_02]),
+        np.array([edge_normal_02]),
    )
@@ -13,7 +13,6 @@
 # limitations under the License.
 # ==============================================================================
 """Engine support functions."""
 from typing import Optional, Tuple, Union
 import jax
@@ -14,14 +14,96 @@
 # ==============================================================================
 """Utilities for testing."""
 import os
 import sys
 import time
 from typing import Dict, Tuple
 from xml.etree import ElementTree as ET
 from etils import epath
 import jax
 import mujoco
 # pylint: disable=g-importing-member
 from mujoco.mjx._src import forward
 from mujoco.mjx._src import io
 # pylint: enable=g-importing-member
 import numpy as np
 def _measure(fn, *args) -> Tuple[float, float]:
  """Reports jit time and op time for a function."""
  beg = time.perf_counter()
  compiled_fn = fn.lower(*args).compile()
  end = time.perf_counter()
  jit_time = end - beg
  beg = time.perf_counter()
  result = compiled_fn(*args)
  jax.block_until_ready(result)
  end = time.perf_counter()
  run_time = end - beg
  return jit_time, run_time
 def benchmark(
    m: mujoco.MjModel,
    nstep: int = 1000,
    batch_size: int = 1024,
    unroll_steps: int = 1,
    solver: str = 'cg',
    iterations: int = 1,
    ls_iterations: int = 4,
 ) -> Tuple[float, float, int]:
  """Benchmark a model."""
  xla_flags = os.environ.get('XLA_FLAGS', '')
  xla_flags += ' --xla_gpu_triton_gemm_any=True'
  os.environ['XLA_FLAGS'] = xla_flags
  m.opt.solver = {
      'cg': mujoco.mjtSolver.mjSOL_CG,
      'newton': mujoco.mjtSolver.mjSOL_NEWTON,
  }[solver.lower()]
  m.opt.iterations = iterations
  m.opt.ls_iterations = ls_iterations
  m = io.put_model(m)
  @jax.pmap
  def init(key):
    key = jax.random.split(key, batch_size // jax.device_count())
    @jax.vmap
    def random_init(key):
      d = io.make_data(m)
      qvel = 0.01 * jax.random.normal(key, shape=(m.nv,))
      d = d.replace(qvel=qvel)
      return d
    return random_init(key)
  key = jax.random.split(jax.random.key(0), jax.device_count())
  d = init(key)
  jax.block_until_ready(d)
  @jax.pmap
  def unroll(d):
    @jax.vmap
    def step(d, _):
      d = forward.step(m, d)
      return d, None
    d, _ = jax.lax.scan(step, d, None, length=nstep, unroll=unroll_steps)
    return d
  jit_time, run_time = _measure(unroll, d)
  steps = nstep * batch_size
  return jit_time, run_time, steps
 _ACTUATOR_TYPES = ['motor', 'velocity', 'position', 'general', 'intvelocity']
 _DYN_TYPES = ['none', 'integrator', 'filter', 'filterexact']
 _DYN_PRMS = ['0.189', '2.1']
@@ -543,8 +543,8 @@ class Model(PyTreeNode):
  geom_convex_vert: List[Optional[jax.Array]]
  geom_convex_edge_dir: List[Optional[jax.Array]]
  geom_convex_facenormal: List[Optional[jax.Array]]
-  geom_convex_face_edge: List[Optional[jax.Array]]
+  geom_convex_edge: List[Optional[jax.Array]]
-  geom_convex_face_edge_normal: List[Optional[jax.Array]]
+  geom_convex_edge_face_normal: List[Optional[jax.Array]]
  pair_solref: jax.Array
  pair_solreffriction: jax.Array
  pair_solimp: jax.Array
@@ -0,0 +1,150 @@
 <mujoco model="01 Humanoids">
  <option timestep="0.005" solver="Newton" iterations="1" ls_iterations="4">
    <flag eulerdamp="disable"/>
  </option>
  <custom>
    <numeric data="4" name="max_contact_points"/>
  </custom>
  <size memory="100M"/>
  <asset>
    <texture type="skybox" builtin="gradient" rgb1=".3 .5 .7" rgb2="0 0 0" width="512" height="512"/>
    <texture name="body" type="cube" builtin="flat" mark="cross" width="128" height="128"
             rgb1="0.8 0.6 0.4" rgb2="0.8 0.6 0.4" markrgb="1 1 1" random="0.01"/>
    <material name="body" texture="body" texuniform="true" rgba="0.8 0.6 .4 1"/>
    <texture name="grid" type="2d" builtin="checker" width="512" height="512" rgb1=".1 .2 .3" rgb2=".2 .3 .4"/>
    <material name="grid" texture="grid" texrepeat="1 1" texuniform="true" reflectance=".2"/>
  </asset>
  <default>
    <motor ctrlrange="-1 1" ctrllimited="true"/>
    <default class="body">
      <geom type="capsule" condim="3" friction=".7" solimp=".9 .99 .003" solref=".015 1" material="body" contype="0"/>
      <joint type="hinge" damping=".2" stiffness="1" armature=".01" limited="true" solimplimit="0 .99 .01"/>
      <default class="big_joint">
        <joint damping="5" stiffness="10"/>
        <default class="big_stiff_joint">
          <joint stiffness="20"/>
        </default>
      </default>
    </default>
  </default>
  <visual>
    <map force="0.1" zfar="30"/>
    <rgba haze="0.15 0.25 0.35 1"/>
    <quality shadowsize="4096"/>
    <global offwidth="800" offheight="800"/>
  </visual>
  <worldbody>
    <geom size="10 10 .05" type="plane" material="grid" condim="3"/>
    <light dir=".2 1 -.4" diffuse=".8 .8 .8" specular="0.3 0.3 0.3" pos="-2 -10 4" cutoff="35"/>
    <light dir="-.2 1 -.4" diffuse=".8 .8 .8" specular="0.3 0.3 0.3" pos="2 -10 4" cutoff="35"/>
    <body name="1a_torso" pos="-1 0 1.5" childclass="body">
      <camera name="1a_back" pos="-3 0 1" xyaxes="0 -1 0 1 0 2" mode="trackcom"/>
      <camera name="1a_side" pos="0 -3 1" xyaxes="1 0 0 0 1 2" mode="trackcom"/>
      <freejoint name="1a_root"/>
      <geom name="1a_torso" fromto="0 -.07 0 0 .07 0" size=".07"/>
      <geom name="1a_upper_waist" fromto="-.01 -.06 -.12 -.01 .06 -.12" size=".06"/>
      <body name="1a_head" pos="0 0 .19">
        <geom name="1a_head" type="sphere" size=".09"/>
        <camera name="1a_egocentric" pos=".09 0 0" xyaxes="0 -1 0 .1 0 1" fovy="80"/>
      </body>
      <body name="1a_lower_waist" pos="-.01 0 -.26">
        <geom name="1a_lower_waist" fromto="0 -.06 0 0 .06 0" size=".06"/>
        <joint name="1a_abdomen_z" pos="0 0 .065" axis="0 0 1" range="-45 45" class="big_stiff_joint"/>
        <joint name="1a_abdomen_y" pos="0 0 .065" axis="0 1 0" range="-75 30" class="big_joint"/>
        <body name="1a_pelvis" pos="0 0 -.165">
          <joint name="1a_abdomen_x" pos="0 0 .1" axis="1 0 0" range="-35 35" class="big_joint"/>
          <geom name="1a_butt" fromto="-.02 -.07 0 -.02 .07 0" size=".09"/>
          <body name="1a_right_thigh" pos="0 -.1 -.04">
            <joint name="1a_right_hip_x" axis="1 0 0" range="-25 5" class="big_joint"/>
            <joint name="1a_right_hip_z" axis="0 0 1" range="-60 35" class="big_joint"/>
            <joint name="1a_right_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="1a_right_thigh" fromto="0 0 0 0 .01 -.34" size=".06"/>
            <body name="1a_right_shin" pos="0 .01 -.403">
              <joint name="1a_right_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="1a_right_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="1a_right_foot" pos="0 0 -.39">
                <joint name="1a_right_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="1a_right_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="1a_right_right_foot" fromto="-.07 -.02 0 .14 -.04 0" size=".027"/>
                <geom name="1a_left_right_foot" fromto="-.07 0 0 .14  .02 0" size=".027"/>
              </body>
            </body>
          </body>
          <body name="1a_left_thigh" pos="0 .1 -.04">
            <joint name="1a_left_hip_x" axis="-1 0 0" range="-25 5" class="big_joint"/>
            <joint name="1a_left_hip_z" axis="0 0 -1" range="-60 35" class="big_joint"/>
            <joint name="1a_left_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="1a_left_thigh" fromto="0 0 0 0 -.01 -.34" size=".06"/>
            <body name="1a_left_shin" pos="0 -.01 -.403">
              <joint name="1a_left_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="1a_left_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="1a_left_foot" pos="0 0 -.39">
                <joint name="1a_left_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="1a_left_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="1a_left_left_foot" fromto="-.07 .02 0 .14 .04 0" size=".027"/>
                <geom name="1a_right_left_foot" fromto="-.07 0 0 .14 -.02 0" size=".027"/>
              </body>
            </body>
          </body>
        </body>
      </body>
      <body name="1a_right_upper_arm" pos="0 -.17 .06">
        <joint name="1a_right_shoulder1" axis="2 1 1"  range="-85 60"/>
        <joint name="1a_right_shoulder2" axis="0 -1 1" range="-85 60"/>
        <geom name="1a_right_upper_arm" fromto="0 0 0 .16 -.16 -.16" size=".04 .16"/>
        <body name="1a_right_lower_arm" pos=".18 -.18 -.18">
          <joint name="1a_right_elbow" axis="0 -1 1" range="-90 50" stiffness="0"/>
          <geom name="1a_right_lower_arm" fromto=".01 .01 .01 .17 .17 .17" size=".031"/>
          <body name="1a_right_hand" pos=".18 .18 .18">
            <geom name="1a_right_hand" type="sphere" size=".04" zaxis="1 1 1"/>
          </body>
        </body>
      </body>
      <body name="1a_left_upper_arm" pos="0 .17 .06">
        <joint name="1a_left_shoulder1" axis="2 -1 1" range="-60 85"/>
        <joint name="1a_left_shoulder2" axis="0 1 1"  range="-60 85"/>
        <geom name="1a_left_upper_arm" fromto="0 0 0 .16 .16 -.16" size=".04 .16"/>
        <body name="1a_left_lower_arm" pos=".18 .18 -.18">
          <joint name="1a_left_elbow" axis="0 -1 -1" range="-90 50" stiffness="0"/>
          <geom name="1a_left_lower_arm" fromto=".01 -.01 .01 .17 -.17 .17" size=".031"/>
          <body name="1a_left_hand" pos=".18 -.18 .18">
            <geom name="1a_left_hand" type="sphere" size=".04" zaxis="1 -1 1"/>
          </body>
        </body>
      </body>
    </body>
  </worldbody>
  <actuator>
    <motor gear="40"  joint="1a_abdomen_y"/>
    <motor gear="40"  joint="1a_abdomen_z"/>
    <motor gear="40"  joint="1a_abdomen_x"/>
    <motor gear="40"  joint="1a_right_hip_x"/>
    <motor gear="40"  joint="1a_right_hip_z"/>
    <motor gear="120" joint="1a_right_hip_y"/>
    <motor gear="80"  joint="1a_right_knee"/>
    <motor gear="20"  joint="1a_right_ankle_x"/>
    <motor gear="20"  joint="1a_right_ankle_y"/>
    <motor gear="40"  joint="1a_left_hip_x"/>
    <motor gear="40"  joint="1a_left_hip_z"/>
    <motor gear="120" joint="1a_left_hip_y"/>
    <motor gear="80"  joint="1a_left_knee"/>
    <motor gear="20"  joint="1a_left_ankle_x"/>
    <motor gear="20"  joint="1a_left_ankle_y"/>
    <motor gear="20"  joint="1a_right_shoulder1"/>
    <motor gear="20"  joint="1a_right_shoulder2"/>
    <motor gear="40"  joint="1a_right_elbow"/>
    <motor gear="20"  joint="1a_left_shoulder1"/>
    <motor gear="20"  joint="1a_left_shoulder2"/>
    <motor gear="40"  joint="1a_left_elbow"/>
  </actuator>
 </mujoco>
@@ -0,0 +1,255 @@
 <mujoco model="02 Humanoids">
  <option timestep="0.005" solver="Newton" iterations="1" ls_iterations="4">
    <flag eulerdamp="disable"/>
  </option>
  <custom>
    <numeric data="8" name="max_contact_points"/>
    <numeric data="8" name="max_geom_pairs"/>
  </custom>
  <size memory="100M"/>
  <asset>
    <texture type="skybox" builtin="gradient" rgb1=".3 .5 .7" rgb2="0 0 0" width="512" height="512"/>
    <texture name="body" type="cube" builtin="flat" mark="cross" width="128" height="128"
             rgb1="0.8 0.6 0.4" rgb2="0.8 0.6 0.4" markrgb="1 1 1" random="0.01"/>
    <material name="body" texture="body" texuniform="true" rgba="0.8 0.6 .4 1"/>
    <texture name="grid" type="2d" builtin="checker" width="512" height="512" rgb1=".1 .2 .3" rgb2=".2 .3 .4"/>
    <material name="grid" texture="grid" texrepeat="1 1" texuniform="true" reflectance=".2"/>
  </asset>
  <default>
    <motor ctrlrange="-1 1" ctrllimited="true"/>
    <joint type="hinge" damping=".2" stiffness="1" armature=".01" limited="true" solimplimit="0 .99 .01"/>
    <default class="big_joint">
      <joint damping="5" stiffness="10"/>
      <default class="big_stiff_joint">
        <joint stiffness="20"/>
      </default>
    </default>
    <default class="body1">
      <geom type="capsule" condim="3" friction=".7" solimp=".9 .99 .003" solref=".015 1" material="body" contype="2" conaffinity="5"/>
    </default>
    <default class="body2">
      <geom type="capsule" condim="3" friction=".7" solimp=".9 .99 .003" solref=".015 1" material="body" contype="4" conaffinity="3"/>
    </default>
  </default>
  <visual>
    <map force="0.1" zfar="30"/>
    <rgba haze="0.15 0.25 0.35 1"/>
    <quality shadowsize="4096"/>
    <global offwidth="800" offheight="800"/>
  </visual>
  <worldbody>
    <geom size="10 10 .05" type="plane" material="grid" condim="3"/>
    <light dir=".2 1 -.4" diffuse=".8 .8 .8" specular="0.3 0.3 0.3" pos="-2 -10 4" cutoff="35"/>
    <light dir="-.2 1 -.4" diffuse=".8 .8 .8" specular="0.3 0.3 0.3" pos="2 -10 4" cutoff="35"/>
    <body name="1a_torso" pos="-1 0 1.5" childclass="body1">
      <camera name="1a_back" pos="-3 0 1" xyaxes="0 -1 0 1 0 2" mode="trackcom"/>
      <camera name="1a_side" pos="0 -3 1" xyaxes="1 0 0 0 1 2" mode="trackcom"/>
      <freejoint name="1a_root"/>
      <geom name="1a_torso" fromto="0 -.07 0 0 .07 0" size=".07"/>
      <geom name="1a_upper_waist" fromto="-.01 -.06 -.12 -.01 .06 -.12" size=".06"/>
      <body name="1a_head" pos="0 0 .19">
        <geom name="1a_head" type="sphere" size=".09"/>
        <camera name="1a_egocentric" pos=".09 0 0" xyaxes="0 -1 0 .1 0 1" fovy="80"/>
      </body>
      <body name="1a_lower_waist" pos="-.01 0 -.26">
        <geom name="1a_lower_waist" fromto="0 -.06 0 0 .06 0" size=".06"/>
        <joint name="1a_abdomen_z" pos="0 0 .065" axis="0 0 1" range="-45 45" class="big_stiff_joint"/>
        <joint name="1a_abdomen_y" pos="0 0 .065" axis="0 1 0" range="-75 30" class="big_joint"/>
        <body name="1a_pelvis" pos="0 0 -.165">
          <joint name="1a_abdomen_x" pos="0 0 .1" axis="1 0 0" range="-35 35" class="big_joint"/>
          <geom name="1a_butt" fromto="-.02 -.07 0 -.02 .07 0" size=".09"/>
          <body name="1a_right_thigh" pos="0 -.1 -.04">
            <joint name="1a_right_hip_x" axis="1 0 0" range="-25 5" class="big_joint"/>
            <joint name="1a_right_hip_z" axis="0 0 1" range="-60 35" class="big_joint"/>
            <joint name="1a_right_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="1a_right_thigh" fromto="0 0 0 0 .01 -.34" size=".06"/>
            <body name="1a_right_shin" pos="0 .01 -.403">
              <joint name="1a_right_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="1a_right_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="1a_right_foot" pos="0 0 -.39">
                <joint name="1a_right_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="1a_right_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="1a_right_right_foot" fromto="-.07 -.02 0 .14 -.04 0" size=".027"/>
                <geom name="1a_left_right_foot" fromto="-.07 0 0 .14  .02 0" size=".027"/>
              </body>
            </body>
          </body>
          <body name="1a_left_thigh" pos="0 .1 -.04">
            <joint name="1a_left_hip_x" axis="-1 0 0" range="-25 5" class="big_joint"/>
            <joint name="1a_left_hip_z" axis="0 0 -1" range="-60 35" class="big_joint"/>
            <joint name="1a_left_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="1a_left_thigh" fromto="0 0 0 0 -.01 -.34" size=".06"/>
            <body name="1a_left_shin" pos="0 -.01 -.403">
              <joint name="1a_left_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="1a_left_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="1a_left_foot" pos="0 0 -.39">
                <joint name="1a_left_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="1a_left_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="1a_left_left_foot" fromto="-.07 .02 0 .14 .04 0" size=".027"/>
                <geom name="1a_right_left_foot" fromto="-.07 0 0 .14 -.02 0" size=".027"/>
              </body>
            </body>
          </body>
        </body>
      </body>
      <body name="1a_right_upper_arm" pos="0 -.17 .06">
        <joint name="1a_right_shoulder1" axis="2 1 1"  range="-85 60"/>
        <joint name="1a_right_shoulder2" axis="0 -1 1" range="-85 60"/>
        <geom name="1a_right_upper_arm" fromto="0 0 0 .16 -.16 -.16" size=".04 .16"/>
        <body name="1a_right_lower_arm" pos=".18 -.18 -.18">
          <joint name="1a_right_elbow" axis="0 -1 1" range="-90 50" stiffness="0"/>
          <geom name="1a_right_lower_arm" fromto=".01 .01 .01 .17 .17 .17" size=".031"/>
          <body name="1a_right_hand" pos=".18 .18 .18">
            <geom name="1a_right_hand" type="sphere" size=".04" zaxis="1 1 1"/>
          </body>
        </body>
      </body>
      <body name="1a_left_upper_arm" pos="0 .17 .06">
        <joint name="1a_left_shoulder1" axis="2 -1 1" range="-60 85"/>
        <joint name="1a_left_shoulder2" axis="0 1 1"  range="-60 85"/>
        <geom name="1a_left_upper_arm" fromto="0 0 0 .16 .16 -.16" size=".04 .16"/>
        <body name="1a_left_lower_arm" pos=".18 .18 -.18">
          <joint name="1a_left_elbow" axis="0 -1 -1" range="-90 50" stiffness="0"/>
          <geom name="1a_left_lower_arm" fromto=".01 -.01 .01 .17 -.17 .17" size=".031"/>
          <body name="1a_left_hand" pos=".18 -.18 .18">
            <geom name="1a_left_hand" type="sphere" size=".04" zaxis="1 -1 1"/>
          </body>
        </body>
      </body>
    </body>
    <body name="2a_torso" pos="-1 1 1.5" childclass="body2">
      <camera name="2a_back" pos="-3 0 1" xyaxes="0 -1 0 1 0 2" mode="trackcom"/>
      <camera name="2a_side" pos="0 -3 1" xyaxes="1 0 0 0 1 2" mode="trackcom"/>
      <freejoint name="2a_root"/>
      <geom name="2a_torso" fromto="0 -.07 0 0 .07 0" size=".07"/>
      <geom name="2a_upper_waist" fromto="-.01 -.06 -.12 -.01 .06 -.12" size=".06"/>
      <body name="2a_head" pos="0 0 .19">
        <geom name="2a_head" type="sphere" size=".09"/>
        <camera name="2a_egocentric" pos=".09 0 0" xyaxes="0 -1 0 .1 0 1" fovy="80"/>
      </body>
      <body name="2a_lower_waist" pos="-.01 0 -.26">
        <geom name="2a_lower_waist" fromto="0 -.06 0 0 .06 0" size=".06"/>
        <joint name="2a_abdomen_z" pos="0 0 .065" axis="0 0 1" range="-45 45" class="big_stiff_joint"/>
        <joint name="2a_abdomen_y" pos="0 0 .065" axis="0 1 0" range="-75 30" class="big_joint"/>
        <body name="2a_pelvis" pos="0 0 -.165">
          <joint name="2a_abdomen_x" pos="0 0 .1" axis="1 0 0" range="-35 35" class="big_joint"/>
          <geom name="2a_butt" fromto="-.02 -.07 0 -.02 .07 0" size=".09"/>
          <body name="2a_right_thigh" pos="0 -.1 -.04">
            <joint name="2a_right_hip_x" axis="1 0 0" range="-25 5" class="big_joint"/>
            <joint name="2a_right_hip_z" axis="0 0 1" range="-60 35" class="big_joint"/>
            <joint name="2a_right_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="2a_right_thigh" fromto="0 0 0 0 .01 -.34" size=".06"/>
            <body name="2a_right_shin" pos="0 .01 -.403">
              <joint name="2a_right_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="2a_right_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="2a_right_foot" pos="0 0 -.39">
                <joint name="2a_right_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="2a_right_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="2a_right_right_foot" fromto="-.07 -.02 0 .14 -.04 0" size=".027"/>
                <geom name="2a_left_right_foot" fromto="-.07 0 0 .14  .02 0" size=".027"/>
              </body>
            </body>
          </body>
          <body name="2a_left_thigh" pos="0 .1 -.04">
            <joint name="2a_left_hip_x" axis="-1 0 0" range="-25 5" class="big_joint"/>
            <joint name="2a_left_hip_z" axis="0 0 -1" range="-60 35" class="big_joint"/>
            <joint name="2a_left_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="2a_left_thigh" fromto="0 0 0 0 -.01 -.34" size=".06"/>
            <body name="2a_left_shin" pos="0 -.01 -.403">
              <joint name="2a_left_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="2a_left_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="2a_left_foot" pos="0 0 -.39">
                <joint name="2a_left_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="2a_left_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="2a_left_left_foot" fromto="-.07 .02 0 .14 .04 0" size=".027"/>
                <geom name="2a_right_left_foot" fromto="-.07 0 0 .14 -.02 0" size=".027"/>
              </body>
            </body>
          </body>
        </body>
      </body>
      <body name="2a_right_upper_arm" pos="0 -.17 .06">
        <joint name="2a_right_shoulder1" axis="2 1 1"  range="-85 60"/>
        <joint name="2a_right_shoulder2" axis="0 -1 1" range="-85 60"/>
        <geom name="2a_right_upper_arm" fromto="0 0 0 .16 -.16 -.16" size=".04 .16"/>
        <body name="2a_right_lower_arm" pos=".18 -.18 -.18">
          <joint name="2a_right_elbow" axis="0 -1 1" range="-90 50" stiffness="0"/>
          <geom name="2a_right_lower_arm" fromto=".01 .01 .01 .17 .17 .17" size=".031"/>
          <body name="2a_right_hand" pos=".18 .18 .18">
            <geom name="2a_right_hand" type="sphere" size=".04" zaxis="1 1 1"/>
          </body>
        </body>
      </body>
      <body name="2a_left_upper_arm" pos="0 .17 .06">
        <joint name="2a_left_shoulder1" axis="2 -1 1" range="-60 85"/>
        <joint name="2a_left_shoulder2" axis="0 1 1"  range="-60 85"/>
        <geom name="2a_left_upper_arm" fromto="0 0 0 .16 .16 -.16" size=".04 .16"/>
        <body name="2a_left_lower_arm" pos=".18 .18 -.18">
          <joint name="2a_left_elbow" axis="0 -1 -1" range="-90 50" stiffness="0"/>
          <geom name="2a_left_lower_arm" fromto=".01 -.01 .01 .17 -.17 .17" size=".031"/>
          <body name="2a_left_hand" pos=".18 -.18 .18">
            <geom name="2a_left_hand" type="sphere" size=".04" zaxis="1 -1 1"/>
          </body>
        </body>
      </body>
    </body>
  </worldbody>
  <actuator>
    <motor gear="40"  joint="1a_abdomen_y"/>
    <motor gear="40"  joint="1a_abdomen_z"/>
    <motor gear="40"  joint="1a_abdomen_x"/>
    <motor gear="40"  joint="1a_right_hip_x"/>
    <motor gear="40"  joint="1a_right_hip_z"/>
    <motor gear="120" joint="1a_right_hip_y"/>
    <motor gear="80"  joint="1a_right_knee"/>
    <motor gear="20"  joint="1a_right_ankle_x"/>
    <motor gear="20"  joint="1a_right_ankle_y"/>
    <motor gear="40"  joint="1a_left_hip_x"/>
    <motor gear="40"  joint="1a_left_hip_z"/>
    <motor gear="120" joint="1a_left_hip_y"/>
    <motor gear="80"  joint="1a_left_knee"/>
    <motor gear="20"  joint="1a_left_ankle_x"/>
    <motor gear="20"  joint="1a_left_ankle_y"/>
    <motor gear="20"  joint="1a_right_shoulder1"/>
    <motor gear="20"  joint="1a_right_shoulder2"/>
    <motor gear="40"  joint="1a_right_elbow"/>
    <motor gear="20"  joint="1a_left_shoulder1"/>
    <motor gear="20"  joint="1a_left_shoulder2"/>
    <motor gear="40"  joint="1a_left_elbow"/>
  </actuator>
  <actuator>
    <motor gear="40"  joint="2a_abdomen_y"/>
    <motor gear="40"  joint="2a_abdomen_z"/>
    <motor gear="40"  joint="2a_abdomen_x"/>
    <motor gear="40"  joint="2a_right_hip_x"/>
    <motor gear="40"  joint="2a_right_hip_z"/>
    <motor gear="120" joint="2a_right_hip_y"/>
    <motor gear="80"  joint="2a_right_knee"/>
    <motor gear="20"  joint="2a_right_ankle_x"/>
    <motor gear="20"  joint="2a_right_ankle_y"/>
    <motor gear="40"  joint="2a_left_hip_x"/>
    <motor gear="40"  joint="2a_left_hip_z"/>
    <motor gear="120" joint="2a_left_hip_y"/>
    <motor gear="80"  joint="2a_left_knee"/>
    <motor gear="20"  joint="2a_left_ankle_x"/>
    <motor gear="20"  joint="2a_left_ankle_y"/>
    <motor gear="20"  joint="2a_right_shoulder1"/>
    <motor gear="20"  joint="2a_right_shoulder2"/>
    <motor gear="40"  joint="2a_right_elbow"/>
    <motor gear="20"  joint="2a_left_shoulder1"/>
    <motor gear="20"  joint="2a_left_shoulder2"/>
    <motor gear="40"  joint="2a_left_elbow"/>
  </actuator>
 </mujoco>
@@ -0,0 +1,359 @@
 <mujoco model="03 Humanoids">
  <option timestep="0.005" solver="Newton" iterations="1" ls_iterations="4">
    <flag eulerdamp="disable"/>
  </option>
  <custom>
    <numeric data="12" name="max_contact_points"/>
    <numeric data="12" name="max_geom_pairs"/>
  </custom>
  <size memory="100M"/>
  <asset>
    <texture type="skybox" builtin="gradient" rgb1=".3 .5 .7" rgb2="0 0 0" width="512" height="512"/>
    <texture name="body" type="cube" builtin="flat" mark="cross" width="128" height="128"
             rgb1="0.8 0.6 0.4" rgb2="0.8 0.6 0.4" markrgb="1 1 1" random="0.01"/>
    <material name="body" texture="body" texuniform="true" rgba="0.8 0.6 .4 1"/>
    <texture name="grid" type="2d" builtin="checker" width="512" height="512" rgb1=".1 .2 .3" rgb2=".2 .3 .4"/>
    <material name="grid" texture="grid" texrepeat="1 1" texuniform="true" reflectance=".2"/>
  </asset>
  <default>
    <motor ctrlrange="-1 1" ctrllimited="true"/>
    <joint type="hinge" damping=".2" stiffness="1" armature=".01" limited="true" solimplimit="0 .99 .01"/>
    <default class="big_joint">
      <joint damping="5" stiffness="10"/>
      <default class="big_stiff_joint">
        <joint stiffness="20"/>
      </default>
    </default>
    <default class="body1">
      <geom type="capsule" condim="3" friction=".7" solimp=".9 .99 .003" solref=".015 1" material="body" contype="2" conaffinity="13"/>
    </default>
    <default class="body2">
      <geom type="capsule" condim="3" friction=".7" solimp=".9 .99 .003" solref=".015 1" material="body" contype="4" conaffinity="11"/>
    </default>
    <default class="body3">
      <geom type="capsule" condim="3" friction=".7" solimp=".9 .99 .003" solref=".015 1" material="body" contype="8" conaffinity="7"/>
    </default>
  </default>
  <visual>
    <map force="0.1" zfar="30"/>
    <rgba haze="0.15 0.25 0.35 1"/>
    <quality shadowsize="4096"/>
    <global offwidth="800" offheight="800"/>
  </visual>
  <worldbody>
    <geom size="10 10 .05" type="plane" material="grid" condim="3"/>
    <light dir=".2 1 -.4" diffuse=".8 .8 .8" specular="0.3 0.3 0.3" pos="-2 -10 4" cutoff="35"/>
    <light dir="-.2 1 -.4" diffuse=".8 .8 .8" specular="0.3 0.3 0.3" pos="2 -10 4" cutoff="35"/>
    <body name="1a_torso" pos="-1 0 1.5" childclass="body1">
      <camera name="1a_back" pos="-3 0 1" xyaxes="0 -1 0 1 0 2" mode="trackcom"/>
      <camera name="1a_side" pos="0 -3 1" xyaxes="1 0 0 0 1 2" mode="trackcom"/>
      <freejoint name="1a_root"/>
      <geom name="1a_torso" fromto="0 -.07 0 0 .07 0" size=".07"/>
      <geom name="1a_upper_waist" fromto="-.01 -.06 -.12 -.01 .06 -.12" size=".06"/>
      <body name="1a_head" pos="0 0 .19">
        <geom name="1a_head" type="sphere" size=".09"/>
        <camera name="1a_egocentric" pos=".09 0 0" xyaxes="0 -1 0 .1 0 1" fovy="80"/>
      </body>
      <body name="1a_lower_waist" pos="-.01 0 -.26">
        <geom name="1a_lower_waist" fromto="0 -.06 0 0 .06 0" size=".06"/>
        <joint name="1a_abdomen_z" pos="0 0 .065" axis="0 0 1" range="-45 45" class="big_stiff_joint"/>
        <joint name="1a_abdomen_y" pos="0 0 .065" axis="0 1 0" range="-75 30" class="big_joint"/>
        <body name="1a_pelvis" pos="0 0 -.165">
          <joint name="1a_abdomen_x" pos="0 0 .1" axis="1 0 0" range="-35 35" class="big_joint"/>
          <geom name="1a_butt" fromto="-.02 -.07 0 -.02 .07 0" size=".09"/>
          <body name="1a_right_thigh" pos="0 -.1 -.04">
            <joint name="1a_right_hip_x" axis="1 0 0" range="-25 5" class="big_joint"/>
            <joint name="1a_right_hip_z" axis="0 0 1" range="-60 35" class="big_joint"/>
            <joint name="1a_right_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="1a_right_thigh" fromto="0 0 0 0 .01 -.34" size=".06"/>
            <body name="1a_right_shin" pos="0 .01 -.403">
              <joint name="1a_right_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="1a_right_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="1a_right_foot" pos="0 0 -.39">
                <joint name="1a_right_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="1a_right_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="1a_right_right_foot" fromto="-.07 -.02 0 .14 -.04 0" size=".027"/>
                <geom name="1a_left_right_foot" fromto="-.07 0 0 .14  .02 0" size=".027"/>
              </body>
            </body>
          </body>
          <body name="1a_left_thigh" pos="0 .1 -.04">
            <joint name="1a_left_hip_x" axis="-1 0 0" range="-25 5" class="big_joint"/>
            <joint name="1a_left_hip_z" axis="0 0 -1" range="-60 35" class="big_joint"/>
            <joint name="1a_left_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="1a_left_thigh" fromto="0 0 0 0 -.01 -.34" size=".06"/>
            <body name="1a_left_shin" pos="0 -.01 -.403">
              <joint name="1a_left_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="1a_left_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="1a_left_foot" pos="0 0 -.39">
                <joint name="1a_left_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="1a_left_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="1a_left_left_foot" fromto="-.07 .02 0 .14 .04 0" size=".027"/>
                <geom name="1a_right_left_foot" fromto="-.07 0 0 .14 -.02 0" size=".027"/>
              </body>
            </body>
          </body>
        </body>
      </body>
      <body name="1a_right_upper_arm" pos="0 -.17 .06">
        <joint name="1a_right_shoulder1" axis="2 1 1"  range="-85 60"/>
        <joint name="1a_right_shoulder2" axis="0 -1 1" range="-85 60"/>
        <geom name="1a_right_upper_arm" fromto="0 0 0 .16 -.16 -.16" size=".04 .16"/>
        <body name="1a_right_lower_arm" pos=".18 -.18 -.18">
          <joint name="1a_right_elbow" axis="0 -1 1" range="-90 50" stiffness="0"/>
          <geom name="1a_right_lower_arm" fromto=".01 .01 .01 .17 .17 .17" size=".031"/>
          <body name="1a_right_hand" pos=".18 .18 .18">
            <geom name="1a_right_hand" type="sphere" size=".04" zaxis="1 1 1"/>
          </body>
        </body>
      </body>
      <body name="1a_left_upper_arm" pos="0 .17 .06">
        <joint name="1a_left_shoulder1" axis="2 -1 1" range="-60 85"/>
        <joint name="1a_left_shoulder2" axis="0 1 1"  range="-60 85"/>
        <geom name="1a_left_upper_arm" fromto="0 0 0 .16 .16 -.16" size=".04 .16"/>
        <body name="1a_left_lower_arm" pos=".18 .18 -.18">
          <joint name="1a_left_elbow" axis="0 -1 -1" range="-90 50" stiffness="0"/>
          <geom name="1a_left_lower_arm" fromto=".01 -.01 .01 .17 -.17 .17" size=".031"/>
          <body name="1a_left_hand" pos=".18 -.18 .18">
            <geom name="1a_left_hand" type="sphere" size=".04" zaxis="1 -1 1"/>
          </body>
        </body>
      </body>
    </body>
    <body name="2a_torso" pos="-1 1 1.5" childclass="body2">
      <camera name="2a_back" pos="-3 0 1" xyaxes="0 -1 0 1 0 2" mode="trackcom"/>
      <camera name="2a_side" pos="0 -3 1" xyaxes="1 0 0 0 1 2" mode="trackcom"/>
      <freejoint name="2a_root"/>
      <geom name="2a_torso" fromto="0 -.07 0 0 .07 0" size=".07"/>
      <geom name="2a_upper_waist" fromto="-.01 -.06 -.12 -.01 .06 -.12" size=".06"/>
      <body name="2a_head" pos="0 0 .19">
        <geom name="2a_head" type="sphere" size=".09"/>
        <camera name="2a_egocentric" pos=".09 0 0" xyaxes="0 -1 0 .1 0 1" fovy="80"/>
      </body>
      <body name="2a_lower_waist" pos="-.01 0 -.26">
        <geom name="2a_lower_waist" fromto="0 -.06 0 0 .06 0" size=".06"/>
        <joint name="2a_abdomen_z" pos="0 0 .065" axis="0 0 1" range="-45 45" class="big_stiff_joint"/>
        <joint name="2a_abdomen_y" pos="0 0 .065" axis="0 1 0" range="-75 30" class="big_joint"/>
        <body name="2a_pelvis" pos="0 0 -.165">
          <joint name="2a_abdomen_x" pos="0 0 .1" axis="1 0 0" range="-35 35" class="big_joint"/>
          <geom name="2a_butt" fromto="-.02 -.07 0 -.02 .07 0" size=".09"/>
          <body name="2a_right_thigh" pos="0 -.1 -.04">
            <joint name="2a_right_hip_x" axis="1 0 0" range="-25 5" class="big_joint"/>
            <joint name="2a_right_hip_z" axis="0 0 1" range="-60 35" class="big_joint"/>
            <joint name="2a_right_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="2a_right_thigh" fromto="0 0 0 0 .01 -.34" size=".06"/>
            <body name="2a_right_shin" pos="0 .01 -.403">
              <joint name="2a_right_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="2a_right_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="2a_right_foot" pos="0 0 -.39">
                <joint name="2a_right_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="2a_right_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="2a_right_right_foot" fromto="-.07 -.02 0 .14 -.04 0" size=".027"/>
                <geom name="2a_left_right_foot" fromto="-.07 0 0 .14  .02 0" size=".027"/>
              </body>
            </body>
          </body>
          <body name="2a_left_thigh" pos="0 .1 -.04">
            <joint name="2a_left_hip_x" axis="-1 0 0" range="-25 5" class="big_joint"/>
            <joint name="2a_left_hip_z" axis="0 0 -1" range="-60 35" class="big_joint"/>
            <joint name="2a_left_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="2a_left_thigh" fromto="0 0 0 0 -.01 -.34" size=".06"/>
            <body name="2a_left_shin" pos="0 -.01 -.403">
              <joint name="2a_left_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="2a_left_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="2a_left_foot" pos="0 0 -.39">
                <joint name="2a_left_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="2a_left_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="2a_left_left_foot" fromto="-.07 .02 0 .14 .04 0" size=".027"/>
                <geom name="2a_right_left_foot" fromto="-.07 0 0 .14 -.02 0" size=".027"/>
              </body>
            </body>
          </body>
        </body>
      </body>
      <body name="2a_right_upper_arm" pos="0 -.17 .06">
        <joint name="2a_right_shoulder1" axis="2 1 1"  range="-85 60"/>
        <joint name="2a_right_shoulder2" axis="0 -1 1" range="-85 60"/>
        <geom name="2a_right_upper_arm" fromto="0 0 0 .16 -.16 -.16" size=".04 .16"/>
        <body name="2a_right_lower_arm" pos=".18 -.18 -.18">
          <joint name="2a_right_elbow" axis="0 -1 1" range="-90 50" stiffness="0"/>
          <geom name="2a_right_lower_arm" fromto=".01 .01 .01 .17 .17 .17" size=".031"/>
          <body name="2a_right_hand" pos=".18 .18 .18">
            <geom name="2a_right_hand" type="sphere" size=".04" zaxis="1 1 1"/>
          </body>
        </body>
      </body>
      <body name="2a_left_upper_arm" pos="0 .17 .06">
        <joint name="2a_left_shoulder1" axis="2 -1 1" range="-60 85"/>
        <joint name="2a_left_shoulder2" axis="0 1 1"  range="-60 85"/>
        <geom name="2a_left_upper_arm" fromto="0 0 0 .16 .16 -.16" size=".04 .16"/>
        <body name="2a_left_lower_arm" pos=".18 .18 -.18">
          <joint name="2a_left_elbow" axis="0 -1 -1" range="-90 50" stiffness="0"/>
          <geom name="2a_left_lower_arm" fromto=".01 -.01 .01 .17 -.17 .17" size=".031"/>
          <body name="2a_left_hand" pos=".18 -.18 .18">
            <geom name="2a_left_hand" type="sphere" size=".04" zaxis="1 -1 1"/>
          </body>
        </body>
      </body>
    </body>
    <body name="3a_torso" pos="-1 -1 1.5" childclass="body3">
      <camera name="3a_back" pos="-3 0 1" xyaxes="0 -1 0 1 0 2" mode="trackcom"/>
      <camera name="3a_side" pos="0 -3 1" xyaxes="1 0 0 0 1 2" mode="trackcom"/>
      <freejoint name="3a_root"/>
      <geom name="3a_torso" fromto="0 -.07 0 0 .07 0" size=".07"/>
      <geom name="3a_upper_waist" fromto="-.01 -.06 -.12 -.01 .06 -.12" size=".06"/>
      <body name="3a_head" pos="0 0 .19">
        <geom name="3a_head" type="sphere" size=".09"/>
        <camera name="3a_egocentric" pos=".09 0 0" xyaxes="0 -1 0 .1 0 1" fovy="80"/>
      </body>
      <body name="3a_lower_waist" pos="-.01 0 -.26">
        <geom name="3a_lower_waist" fromto="0 -.06 0 0 .06 0" size=".06"/>
        <joint name="3a_abdomen_z" pos="0 0 .065" axis="0 0 1" range="-45 45" class="big_stiff_joint"/>
        <joint name="3a_abdomen_y" pos="0 0 .065" axis="0 1 0" range="-75 30" class="big_joint"/>
        <body name="3a_pelvis" pos="0 0 -.165">
          <joint name="3a_abdomen_x" pos="0 0 .1" axis="1 0 0" range="-35 35" class="big_joint"/>
          <geom name="3a_butt" fromto="-.02 -.07 0 -.02 .07 0" size=".09"/>
          <body name="3a_right_thigh" pos="0 -.1 -.04">
            <joint name="3a_right_hip_x" axis="1 0 0" range="-25 5" class="big_joint"/>
            <joint name="3a_right_hip_z" axis="0 0 1" range="-60 35" class="big_joint"/>
            <joint name="3a_right_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="3a_right_thigh" fromto="0 0 0 0 .01 -.34" size=".06"/>
            <body name="3a_right_shin" pos="0 .01 -.403">
              <joint name="3a_right_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="3a_right_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="3a_right_foot" pos="0 0 -.39">
                <joint name="3a_right_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="3a_right_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="3a_right_right_foot" fromto="-.07 -.02 0 .14 -.04 0" size=".027"/>
                <geom name="3a_left_right_foot" fromto="-.07 0 0 .14  .02 0" size=".027"/>
              </body>
            </body>
          </body>
          <body name="3a_left_thigh" pos="0 .1 -.04">
            <joint name="3a_left_hip_x" axis="-1 0 0" range="-25 5" class="big_joint"/>
            <joint name="3a_left_hip_z" axis="0 0 -1" range="-60 35" class="big_joint"/>
            <joint name="3a_left_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="3a_left_thigh" fromto="0 0 0 0 -.01 -.34" size=".06"/>
            <body name="3a_left_shin" pos="0 -.01 -.403">
              <joint name="3a_left_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="3a_left_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="3a_left_foot" pos="0 0 -.39">
                <joint name="3a_left_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="3a_left_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="3a_left_left_foot" fromto="-.07 .02 0 .14 .04 0" size=".027"/>
                <geom name="3a_right_left_foot" fromto="-.07 0 0 .14 -.02 0" size=".027"/>
              </body>
            </body>
          </body>
        </body>
      </body>
      <body name="3a_right_upper_arm" pos="0 -.17 .06">
        <joint name="3a_right_shoulder1" axis="2 1 1"  range="-85 60"/>
        <joint name="3a_right_shoulder2" axis="0 -1 1" range="-85 60"/>
        <geom name="3a_right_upper_arm" fromto="0 0 0 .16 -.16 -.16" size=".04 .16"/>
        <body name="3a_right_lower_arm" pos=".18 -.18 -.18">
          <joint name="3a_right_elbow" axis="0 -1 1" range="-90 50" stiffness="0"/>
          <geom name="3a_right_lower_arm" fromto=".01 .01 .01 .17 .17 .17" size=".031"/>
          <body name="3a_right_hand" pos=".18 .18 .18">
            <geom name="3a_right_hand" type="sphere" size=".04" zaxis="1 1 1"/>
          </body>
        </body>
      </body>
      <body name="3a_left_upper_arm" pos="0 .17 .06">
        <joint name="3a_left_shoulder1" axis="2 -1 1" range="-60 85"/>
        <joint name="3a_left_shoulder2" axis="0 1 1"  range="-60 85"/>
        <geom name="3a_left_upper_arm" fromto="0 0 0 .16 .16 -.16" size=".04 .16"/>
        <body name="3a_left_lower_arm" pos=".18 .18 -.18">
          <joint name="3a_left_elbow" axis="0 -1 -1" range="-90 50" stiffness="0"/>
          <geom name="3a_left_lower_arm" fromto=".01 -.01 .01 .17 -.17 .17" size=".031"/>
          <body name="3a_left_hand" pos=".18 -.18 .18">
            <geom name="3a_left_hand" type="sphere" size=".04" zaxis="1 -1 1"/>
          </body>
        </body>
      </body>
    </body>
  </worldbody>
  <actuator>
    <motor gear="40"  joint="1a_abdomen_y"/>
    <motor gear="40"  joint="1a_abdomen_z"/>
    <motor gear="40"  joint="1a_abdomen_x"/>
    <motor gear="40"  joint="1a_right_hip_x"/>
    <motor gear="40"  joint="1a_right_hip_z"/>
    <motor gear="120" joint="1a_right_hip_y"/>
    <motor gear="80"  joint="1a_right_knee"/>
    <motor gear="20"  joint="1a_right_ankle_x"/>
    <motor gear="20"  joint="1a_right_ankle_y"/>
    <motor gear="40"  joint="1a_left_hip_x"/>
    <motor gear="40"  joint="1a_left_hip_z"/>
    <motor gear="120" joint="1a_left_hip_y"/>
    <motor gear="80"  joint="1a_left_knee"/>
    <motor gear="20"  joint="1a_left_ankle_x"/>
    <motor gear="20"  joint="1a_left_ankle_y"/>
    <motor gear="20"  joint="1a_right_shoulder1"/>
    <motor gear="20"  joint="1a_right_shoulder2"/>
    <motor gear="40"  joint="1a_right_elbow"/>
    <motor gear="20"  joint="1a_left_shoulder1"/>
    <motor gear="20"  joint="1a_left_shoulder2"/>
    <motor gear="40"  joint="1a_left_elbow"/>
  </actuator>
  <actuator>
    <motor gear="40"  joint="2a_abdomen_y"/>
    <motor gear="40"  joint="2a_abdomen_z"/>
    <motor gear="40"  joint="2a_abdomen_x"/>
    <motor gear="40"  joint="2a_right_hip_x"/>
    <motor gear="40"  joint="2a_right_hip_z"/>
    <motor gear="120" joint="2a_right_hip_y"/>
    <motor gear="80"  joint="2a_right_knee"/>
    <motor gear="20"  joint="2a_right_ankle_x"/>
    <motor gear="20"  joint="2a_right_ankle_y"/>
    <motor gear="40"  joint="2a_left_hip_x"/>
    <motor gear="40"  joint="2a_left_hip_z"/>
    <motor gear="120" joint="2a_left_hip_y"/>
    <motor gear="80"  joint="2a_left_knee"/>
    <motor gear="20"  joint="2a_left_ankle_x"/>
    <motor gear="20"  joint="2a_left_ankle_y"/>
    <motor gear="20"  joint="2a_right_shoulder1"/>
    <motor gear="20"  joint="2a_right_shoulder2"/>
    <motor gear="40"  joint="2a_right_elbow"/>
    <motor gear="20"  joint="2a_left_shoulder1"/>
    <motor gear="20"  joint="2a_left_shoulder2"/>
    <motor gear="40"  joint="2a_left_elbow"/>
  </actuator>
  <actuator>
    <motor gear="40"  joint="3a_abdomen_y"/>
    <motor gear="40"  joint="3a_abdomen_z"/>
    <motor gear="40"  joint="3a_abdomen_x"/>
    <motor gear="40"  joint="3a_right_hip_x"/>
    <motor gear="40"  joint="3a_right_hip_z"/>
    <motor gear="120" joint="3a_right_hip_y"/>
    <motor gear="80"  joint="3a_right_knee"/>
    <motor gear="20"  joint="3a_right_ankle_x"/>
    <motor gear="20"  joint="3a_right_ankle_y"/>
    <motor gear="40"  joint="3a_left_hip_x"/>
    <motor gear="40"  joint="3a_left_hip_z"/>
    <motor gear="120" joint="3a_left_hip_y"/>
    <motor gear="80"  joint="3a_left_knee"/>
    <motor gear="20"  joint="3a_left_ankle_x"/>
    <motor gear="20"  joint="3a_left_ankle_y"/>
    <motor gear="20"  joint="3a_right_shoulder1"/>
    <motor gear="20"  joint="3a_right_shoulder2"/>
    <motor gear="40"  joint="3a_right_elbow"/>
    <motor gear="20"  joint="3a_left_shoulder1"/>
    <motor gear="20"  joint="3a_left_shoulder2"/>
    <motor gear="40"  joint="3a_left_elbow"/>
  </actuator>
 </mujoco>
@@ -0,0 +1,463 @@
 <mujoco model="04 Humanoids">
  <option timestep="0.005" solver="Newton" iterations="1" ls_iterations="4">
    <flag eulerdamp="disable"/>
  </option>
  <custom>
    <numeric data="16" name="max_contact_points"/>
    <numeric data="16" name="max_geom_pairs"/>
  </custom>
  <size memory="100M"/>
  <asset>
    <texture type="skybox" builtin="gradient" rgb1=".3 .5 .7" rgb2="0 0 0" width="512" height="512"/>
    <texture name="body" type="cube" builtin="flat" mark="cross" width="128" height="128"
             rgb1="0.8 0.6 0.4" rgb2="0.8 0.6 0.4" markrgb="1 1 1" random="0.01"/>
    <material name="body" texture="body" texuniform="true" rgba="0.8 0.6 .4 1"/>
    <texture name="grid" type="2d" builtin="checker" width="512" height="512" rgb1=".1 .2 .3" rgb2=".2 .3 .4"/>
    <material name="grid" texture="grid" texrepeat="1 1" texuniform="true" reflectance=".2"/>
  </asset>
  <default>
    <motor ctrlrange="-1 1" ctrllimited="true"/>
    <joint type="hinge" damping=".2" stiffness="1" armature=".01" limited="true" solimplimit="0 .99 .01"/>
    <default class="big_joint">
      <joint damping="5" stiffness="10"/>
      <default class="big_stiff_joint">
        <joint stiffness="20"/>
      </default>
    </default>
    <default class="body1">
      <geom type="capsule" condim="3" friction=".7" solimp=".9 .99 .003" solref=".015 1" material="body" contype="2" conaffinity="29"/>
    </default>
    <default class="body2">
      <geom type="capsule" condim="3" friction=".7" solimp=".9 .99 .003" solref=".015 1" material="body" contype="4" conaffinity="27"/>
    </default>
    <default class="body3">
      <geom type="capsule" condim="3" friction=".7" solimp=".9 .99 .003" solref=".015 1" material="body" contype="8" conaffinity="23"/>
    </default>
    <default class="body4">
      <geom type="capsule" condim="3" friction=".7" solimp=".9 .99 .003" solref=".015 1" material="body" contype="16" conaffinity="15"/>
    </default>
  </default>
  <visual>
    <map force="0.1" zfar="30"/>
    <rgba haze="0.15 0.25 0.35 1"/>
    <quality shadowsize="4096"/>
    <global offwidth="800" offheight="800"/>
  </visual>
  <worldbody>
    <geom size="10 10 .05" type="plane" material="grid" condim="3"/>
    <light dir=".2 1 -.4" diffuse=".8 .8 .8" specular="0.3 0.3 0.3" pos="-2 -10 4" cutoff="35"/>
    <light dir="-.2 1 -.4" diffuse=".8 .8 .8" specular="0.3 0.3 0.3" pos="2 -10 4" cutoff="35"/>
    <body name="1a_torso" pos="-1 0 1.5" childclass="body1">
      <camera name="1a_back" pos="-3 0 1" xyaxes="0 -1 0 1 0 2" mode="trackcom"/>
      <camera name="1a_side" pos="0 -3 1" xyaxes="1 0 0 0 1 2" mode="trackcom"/>
      <freejoint name="1a_root"/>
      <geom name="1a_torso" fromto="0 -.07 0 0 .07 0" size=".07"/>
      <geom name="1a_upper_waist" fromto="-.01 -.06 -.12 -.01 .06 -.12" size=".06"/>
      <body name="1a_head" pos="0 0 .19">
        <geom name="1a_head" type="sphere" size=".09"/>
        <camera name="1a_egocentric" pos=".09 0 0" xyaxes="0 -1 0 .1 0 1" fovy="80"/>
      </body>
      <body name="1a_lower_waist" pos="-.01 0 -.26">
        <geom name="1a_lower_waist" fromto="0 -.06 0 0 .06 0" size=".06"/>
        <joint name="1a_abdomen_z" pos="0 0 .065" axis="0 0 1" range="-45 45" class="big_stiff_joint"/>
        <joint name="1a_abdomen_y" pos="0 0 .065" axis="0 1 0" range="-75 30" class="big_joint"/>
        <body name="1a_pelvis" pos="0 0 -.165">
          <joint name="1a_abdomen_x" pos="0 0 .1" axis="1 0 0" range="-35 35" class="big_joint"/>
          <geom name="1a_butt" fromto="-.02 -.07 0 -.02 .07 0" size=".09"/>
          <body name="1a_right_thigh" pos="0 -.1 -.04">
            <joint name="1a_right_hip_x" axis="1 0 0" range="-25 5" class="big_joint"/>
            <joint name="1a_right_hip_z" axis="0 0 1" range="-60 35" class="big_joint"/>
            <joint name="1a_right_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="1a_right_thigh" fromto="0 0 0 0 .01 -.34" size=".06"/>
            <body name="1a_right_shin" pos="0 .01 -.403">
              <joint name="1a_right_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="1a_right_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="1a_right_foot" pos="0 0 -.39">
                <joint name="1a_right_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="1a_right_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="1a_right_right_foot" fromto="-.07 -.02 0 .14 -.04 0" size=".027"/>
                <geom name="1a_left_right_foot" fromto="-.07 0 0 .14  .02 0" size=".027"/>
              </body>
            </body>
          </body>
          <body name="1a_left_thigh" pos="0 .1 -.04">
            <joint name="1a_left_hip_x" axis="-1 0 0" range="-25 5" class="big_joint"/>
            <joint name="1a_left_hip_z" axis="0 0 -1" range="-60 35" class="big_joint"/>
            <joint name="1a_left_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="1a_left_thigh" fromto="0 0 0 0 -.01 -.34" size=".06"/>
            <body name="1a_left_shin" pos="0 -.01 -.403">
              <joint name="1a_left_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="1a_left_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="1a_left_foot" pos="0 0 -.39">
                <joint name="1a_left_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="1a_left_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="1a_left_left_foot" fromto="-.07 .02 0 .14 .04 0" size=".027"/>
                <geom name="1a_right_left_foot" fromto="-.07 0 0 .14 -.02 0" size=".027"/>
              </body>
            </body>
          </body>
        </body>
      </body>
      <body name="1a_right_upper_arm" pos="0 -.17 .06">
        <joint name="1a_right_shoulder1" axis="2 1 1"  range="-85 60"/>
        <joint name="1a_right_shoulder2" axis="0 -1 1" range="-85 60"/>
        <geom name="1a_right_upper_arm" fromto="0 0 0 .16 -.16 -.16" size=".04 .16"/>
        <body name="1a_right_lower_arm" pos=".18 -.18 -.18">
          <joint name="1a_right_elbow" axis="0 -1 1" range="-90 50" stiffness="0"/>
          <geom name="1a_right_lower_arm" fromto=".01 .01 .01 .17 .17 .17" size=".031"/>
          <body name="1a_right_hand" pos=".18 .18 .18">
            <geom name="1a_right_hand" type="sphere" size=".04" zaxis="1 1 1"/>
          </body>
        </body>
      </body>
      <body name="1a_left_upper_arm" pos="0 .17 .06">
        <joint name="1a_left_shoulder1" axis="2 -1 1" range="-60 85"/>
        <joint name="1a_left_shoulder2" axis="0 1 1"  range="-60 85"/>
        <geom name="1a_left_upper_arm" fromto="0 0 0 .16 .16 -.16" size=".04 .16"/>
        <body name="1a_left_lower_arm" pos=".18 .18 -.18">
          <joint name="1a_left_elbow" axis="0 -1 -1" range="-90 50" stiffness="0"/>
          <geom name="1a_left_lower_arm" fromto=".01 -.01 .01 .17 -.17 .17" size=".031"/>
          <body name="1a_left_hand" pos=".18 -.18 .18">
            <geom name="1a_left_hand" type="sphere" size=".04" zaxis="1 -1 1"/>
          </body>
        </body>
      </body>
    </body>
    <body name="2a_torso" pos="-1 1 1.5" childclass="body2">
      <camera name="2a_back" pos="-3 0 1" xyaxes="0 -1 0 1 0 2" mode="trackcom"/>
      <camera name="2a_side" pos="0 -3 1" xyaxes="1 0 0 0 1 2" mode="trackcom"/>
      <freejoint name="2a_root"/>
      <geom name="2a_torso" fromto="0 -.07 0 0 .07 0" size=".07"/>
      <geom name="2a_upper_waist" fromto="-.01 -.06 -.12 -.01 .06 -.12" size=".06"/>
      <body name="2a_head" pos="0 0 .19">
        <geom name="2a_head" type="sphere" size=".09"/>
        <camera name="2a_egocentric" pos=".09 0 0" xyaxes="0 -1 0 .1 0 1" fovy="80"/>
      </body>
      <body name="2a_lower_waist" pos="-.01 0 -.26">
        <geom name="2a_lower_waist" fromto="0 -.06 0 0 .06 0" size=".06"/>
        <joint name="2a_abdomen_z" pos="0 0 .065" axis="0 0 1" range="-45 45" class="big_stiff_joint"/>
        <joint name="2a_abdomen_y" pos="0 0 .065" axis="0 1 0" range="-75 30" class="big_joint"/>
        <body name="2a_pelvis" pos="0 0 -.165">
          <joint name="2a_abdomen_x" pos="0 0 .1" axis="1 0 0" range="-35 35" class="big_joint"/>
          <geom name="2a_butt" fromto="-.02 -.07 0 -.02 .07 0" size=".09"/>
          <body name="2a_right_thigh" pos="0 -.1 -.04">
            <joint name="2a_right_hip_x" axis="1 0 0" range="-25 5" class="big_joint"/>
            <joint name="2a_right_hip_z" axis="0 0 1" range="-60 35" class="big_joint"/>
            <joint name="2a_right_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="2a_right_thigh" fromto="0 0 0 0 .01 -.34" size=".06"/>
            <body name="2a_right_shin" pos="0 .01 -.403">
              <joint name="2a_right_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="2a_right_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="2a_right_foot" pos="0 0 -.39">
                <joint name="2a_right_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="2a_right_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="2a_right_right_foot" fromto="-.07 -.02 0 .14 -.04 0" size=".027"/>
                <geom name="2a_left_right_foot" fromto="-.07 0 0 .14  .02 0" size=".027"/>
              </body>
            </body>
          </body>
          <body name="2a_left_thigh" pos="0 .1 -.04">
            <joint name="2a_left_hip_x" axis="-1 0 0" range="-25 5" class="big_joint"/>
            <joint name="2a_left_hip_z" axis="0 0 -1" range="-60 35" class="big_joint"/>
            <joint name="2a_left_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="2a_left_thigh" fromto="0 0 0 0 -.01 -.34" size=".06"/>
            <body name="2a_left_shin" pos="0 -.01 -.403">
              <joint name="2a_left_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="2a_left_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="2a_left_foot" pos="0 0 -.39">
                <joint name="2a_left_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="2a_left_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="2a_left_left_foot" fromto="-.07 .02 0 .14 .04 0" size=".027"/>
                <geom name="2a_right_left_foot" fromto="-.07 0 0 .14 -.02 0" size=".027"/>
              </body>
            </body>
          </body>
        </body>
      </body>
      <body name="2a_right_upper_arm" pos="0 -.17 .06">
        <joint name="2a_right_shoulder1" axis="2 1 1"  range="-85 60"/>
        <joint name="2a_right_shoulder2" axis="0 -1 1" range="-85 60"/>
        <geom name="2a_right_upper_arm" fromto="0 0 0 .16 -.16 -.16" size=".04 .16"/>
        <body name="2a_right_lower_arm" pos=".18 -.18 -.18">
          <joint name="2a_right_elbow" axis="0 -1 1" range="-90 50" stiffness="0"/>
          <geom name="2a_right_lower_arm" fromto=".01 .01 .01 .17 .17 .17" size=".031"/>
          <body name="2a_right_hand" pos=".18 .18 .18">
            <geom name="2a_right_hand" type="sphere" size=".04" zaxis="1 1 1"/>
          </body>
        </body>
      </body>
      <body name="2a_left_upper_arm" pos="0 .17 .06">
        <joint name="2a_left_shoulder1" axis="2 -1 1" range="-60 85"/>
        <joint name="2a_left_shoulder2" axis="0 1 1"  range="-60 85"/>
        <geom name="2a_left_upper_arm" fromto="0 0 0 .16 .16 -.16" size=".04 .16"/>
        <body name="2a_left_lower_arm" pos=".18 .18 -.18">
          <joint name="2a_left_elbow" axis="0 -1 -1" range="-90 50" stiffness="0"/>
          <geom name="2a_left_lower_arm" fromto=".01 -.01 .01 .17 -.17 .17" size=".031"/>
          <body name="2a_left_hand" pos=".18 -.18 .18">
            <geom name="2a_left_hand" type="sphere" size=".04" zaxis="1 -1 1"/>
          </body>
        </body>
      </body>
    </body>
    <body name="3a_torso" pos="-1 -1 1.5" childclass="body3">
      <camera name="3a_back" pos="-3 0 1" xyaxes="0 -1 0 1 0 2" mode="trackcom"/>
      <camera name="3a_side" pos="0 -3 1" xyaxes="1 0 0 0 1 2" mode="trackcom"/>
      <freejoint name="3a_root"/>
      <geom name="3a_torso" fromto="0 -.07 0 0 .07 0" size=".07"/>
      <geom name="3a_upper_waist" fromto="-.01 -.06 -.12 -.01 .06 -.12" size=".06"/>
      <body name="3a_head" pos="0 0 .19">
        <geom name="3a_head" type="sphere" size=".09"/>
        <camera name="3a_egocentric" pos=".09 0 0" xyaxes="0 -1 0 .1 0 1" fovy="80"/>
      </body>
      <body name="3a_lower_waist" pos="-.01 0 -.26">
        <geom name="3a_lower_waist" fromto="0 -.06 0 0 .06 0" size=".06"/>
        <joint name="3a_abdomen_z" pos="0 0 .065" axis="0 0 1" range="-45 45" class="big_stiff_joint"/>
        <joint name="3a_abdomen_y" pos="0 0 .065" axis="0 1 0" range="-75 30" class="big_joint"/>
        <body name="3a_pelvis" pos="0 0 -.165">
          <joint name="3a_abdomen_x" pos="0 0 .1" axis="1 0 0" range="-35 35" class="big_joint"/>
          <geom name="3a_butt" fromto="-.02 -.07 0 -.02 .07 0" size=".09"/>
          <body name="3a_right_thigh" pos="0 -.1 -.04">
            <joint name="3a_right_hip_x" axis="1 0 0" range="-25 5" class="big_joint"/>
            <joint name="3a_right_hip_z" axis="0 0 1" range="-60 35" class="big_joint"/>
            <joint name="3a_right_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="3a_right_thigh" fromto="0 0 0 0 .01 -.34" size=".06"/>
            <body name="3a_right_shin" pos="0 .01 -.403">
              <joint name="3a_right_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="3a_right_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="3a_right_foot" pos="0 0 -.39">
                <joint name="3a_right_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="3a_right_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="3a_right_right_foot" fromto="-.07 -.02 0 .14 -.04 0" size=".027"/>
                <geom name="3a_left_right_foot" fromto="-.07 0 0 .14  .02 0" size=".027"/>
              </body>
            </body>
          </body>
          <body name="3a_left_thigh" pos="0 .1 -.04">
            <joint name="3a_left_hip_x" axis="-1 0 0" range="-25 5" class="big_joint"/>
            <joint name="3a_left_hip_z" axis="0 0 -1" range="-60 35" class="big_joint"/>
            <joint name="3a_left_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="3a_left_thigh" fromto="0 0 0 0 -.01 -.34" size=".06"/>
            <body name="3a_left_shin" pos="0 -.01 -.403">
              <joint name="3a_left_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="3a_left_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="3a_left_foot" pos="0 0 -.39">
                <joint name="3a_left_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="3a_left_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="3a_left_left_foot" fromto="-.07 .02 0 .14 .04 0" size=".027"/>
                <geom name="3a_right_left_foot" fromto="-.07 0 0 .14 -.02 0" size=".027"/>
              </body>
            </body>
          </body>
        </body>
      </body>
      <body name="3a_right_upper_arm" pos="0 -.17 .06">
        <joint name="3a_right_shoulder1" axis="2 1 1"  range="-85 60"/>
        <joint name="3a_right_shoulder2" axis="0 -1 1" range="-85 60"/>
        <geom name="3a_right_upper_arm" fromto="0 0 0 .16 -.16 -.16" size=".04 .16"/>
        <body name="3a_right_lower_arm" pos=".18 -.18 -.18">
          <joint name="3a_right_elbow" axis="0 -1 1" range="-90 50" stiffness="0"/>
          <geom name="3a_right_lower_arm" fromto=".01 .01 .01 .17 .17 .17" size=".031"/>
          <body name="3a_right_hand" pos=".18 .18 .18">
            <geom name="3a_right_hand" type="sphere" size=".04" zaxis="1 1 1"/>
          </body>
        </body>
      </body>
      <body name="3a_left_upper_arm" pos="0 .17 .06">
        <joint name="3a_left_shoulder1" axis="2 -1 1" range="-60 85"/>
        <joint name="3a_left_shoulder2" axis="0 1 1"  range="-60 85"/>
        <geom name="3a_left_upper_arm" fromto="0 0 0 .16 .16 -.16" size=".04 .16"/>
        <body name="3a_left_lower_arm" pos=".18 .18 -.18">
          <joint name="3a_left_elbow" axis="0 -1 -1" range="-90 50" stiffness="0"/>
          <geom name="3a_left_lower_arm" fromto=".01 -.01 .01 .17 -.17 .17" size=".031"/>
          <body name="3a_left_hand" pos=".18 -.18 .18">
            <geom name="3a_left_hand" type="sphere" size=".04" zaxis="1 -1 1"/>
          </body>
        </body>
      </body>
    </body>
    <body name="4a_torso" pos="-1 2 1.5" childclass="body4">
      <camera name="4a_back" pos="-3 0 1" xyaxes="0 -1 0 1 0 2" mode="trackcom"/>
      <camera name="4a_side" pos="0 -3 1" xyaxes="1 0 0 0 1 2" mode="trackcom"/>
      <freejoint name="4a_root"/>
      <geom name="4a_torso" fromto="0 -.07 0 0 .07 0" size=".07"/>
      <geom name="4a_upper_waist" fromto="-.01 -.06 -.12 -.01 .06 -.12" size=".06"/>
      <body name="4a_head" pos="0 0 .19">
        <geom name="4a_head" type="sphere" size=".09"/>
        <camera name="4a_egocentric" pos=".09 0 0" xyaxes="0 -1 0 .1 0 1" fovy="80"/>
      </body>
      <body name="4a_lower_waist" pos="-.01 0 -.26">
        <geom name="4a_lower_waist" fromto="0 -.06 0 0 .06 0" size=".06"/>
        <joint name="4a_abdomen_z" pos="0 0 .065" axis="0 0 1" range="-45 45" class="big_stiff_joint"/>
        <joint name="4a_abdomen_y" pos="0 0 .065" axis="0 1 0" range="-75 30" class="big_joint"/>
        <body name="4a_pelvis" pos="0 0 -.165">
          <joint name="4a_abdomen_x" pos="0 0 .1" axis="1 0 0" range="-35 35" class="big_joint"/>
          <geom name="4a_butt" fromto="-.02 -.07 0 -.02 .07 0" size=".09"/>
          <body name="4a_right_thigh" pos="0 -.1 -.04">
            <joint name="4a_right_hip_x" axis="1 0 0" range="-25 5" class="big_joint"/>
            <joint name="4a_right_hip_z" axis="0 0 1" range="-60 35" class="big_joint"/>
            <joint name="4a_right_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="4a_right_thigh" fromto="0 0 0 0 .01 -.34" size=".06"/>
            <body name="4a_right_shin" pos="0 .01 -.403">
              <joint name="4a_right_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="4a_right_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="4a_right_foot" pos="0 0 -.39">
                <joint name="4a_right_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="4a_right_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="4a_right_right_foot" fromto="-.07 -.02 0 .14 -.04 0" size=".027"/>
                <geom name="4a_left_right_foot" fromto="-.07 0 0 .14  .02 0" size=".027"/>
              </body>
            </body>
          </body>
          <body name="4a_left_thigh" pos="0 .1 -.04">
            <joint name="4a_left_hip_x" axis="-1 0 0" range="-25 5" class="big_joint"/>
            <joint name="4a_left_hip_z" axis="0 0 -1" range="-60 35" class="big_joint"/>
            <joint name="4a_left_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="4a_left_thigh" fromto="0 0 0 0 -.01 -.34" size=".06"/>
            <body name="4a_left_shin" pos="0 -.01 -.403">
              <joint name="4a_left_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="4a_left_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="4a_left_foot" pos="0 0 -.39">
                <joint name="4a_left_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="4a_left_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="4a_left_left_foot" fromto="-.07 .02 0 .14 .04 0" size=".027"/>
                <geom name="4a_right_left_foot" fromto="-.07 0 0 .14 -.02 0" size=".027"/>
              </body>
            </body>
          </body>
        </body>
      </body>
      <body name="4a_right_upper_arm" pos="0 -.17 .06">
        <joint name="4a_right_shoulder1" axis="2 1 1"  range="-85 60"/>
        <joint name="4a_right_shoulder2" axis="0 -1 1" range="-85 60"/>
        <geom name="4a_right_upper_arm" fromto="0 0 0 .16 -.16 -.16" size=".04 .16"/>
        <body name="4a_right_lower_arm" pos=".18 -.18 -.18">
          <joint name="4a_right_elbow" axis="0 -1 1" range="-90 50" stiffness="0"/>
          <geom name="4a_right_lower_arm" fromto=".01 .01 .01 .17 .17 .17" size=".031"/>
          <body name="4a_right_hand" pos=".18 .18 .18">
            <geom name="4a_right_hand" type="sphere" size=".04" zaxis="1 1 1"/>
          </body>
        </body>
      </body>
      <body name="4a_left_upper_arm" pos="0 .17 .06">
        <joint name="4a_left_shoulder1" axis="2 -1 1" range="-60 85"/>
        <joint name="4a_left_shoulder2" axis="0 1 1"  range="-60 85"/>
        <geom name="4a_left_upper_arm" fromto="0 0 0 .16 .16 -.16" size=".04 .16"/>
        <body name="4a_left_lower_arm" pos=".18 .18 -.18">
          <joint name="4a_left_elbow" axis="0 -1 -1" range="-90 50" stiffness="0"/>
          <geom name="4a_left_lower_arm" fromto=".01 -.01 .01 .17 -.17 .17" size=".031"/>
          <body name="4a_left_hand" pos=".18 -.18 .18">
            <geom name="4a_left_hand" type="sphere" size=".04" zaxis="1 -1 1"/>
          </body>
        </body>
      </body>
    </body>
  </worldbody>
  <actuator>
    <motor gear="40"  joint="1a_abdomen_y"/>
    <motor gear="40"  joint="1a_abdomen_z"/>
    <motor gear="40"  joint="1a_abdomen_x"/>
    <motor gear="40"  joint="1a_right_hip_x"/>
    <motor gear="40"  joint="1a_right_hip_z"/>
    <motor gear="120" joint="1a_right_hip_y"/>
    <motor gear="80"  joint="1a_right_knee"/>
    <motor gear="20"  joint="1a_right_ankle_x"/>
    <motor gear="20"  joint="1a_right_ankle_y"/>
    <motor gear="40"  joint="1a_left_hip_x"/>
    <motor gear="40"  joint="1a_left_hip_z"/>
    <motor gear="120" joint="1a_left_hip_y"/>
    <motor gear="80"  joint="1a_left_knee"/>
    <motor gear="20"  joint="1a_left_ankle_x"/>
    <motor gear="20"  joint="1a_left_ankle_y"/>
    <motor gear="20"  joint="1a_right_shoulder1"/>
    <motor gear="20"  joint="1a_right_shoulder2"/>
    <motor gear="40"  joint="1a_right_elbow"/>
    <motor gear="20"  joint="1a_left_shoulder1"/>
    <motor gear="20"  joint="1a_left_shoulder2"/>
    <motor gear="40"  joint="1a_left_elbow"/>
  </actuator>
  <actuator>
    <motor gear="40"  joint="2a_abdomen_y"/>
    <motor gear="40"  joint="2a_abdomen_z"/>
    <motor gear="40"  joint="2a_abdomen_x"/>
    <motor gear="40"  joint="2a_right_hip_x"/>
    <motor gear="40"  joint="2a_right_hip_z"/>
    <motor gear="120" joint="2a_right_hip_y"/>
    <motor gear="80"  joint="2a_right_knee"/>
    <motor gear="20"  joint="2a_right_ankle_x"/>
    <motor gear="20"  joint="2a_right_ankle_y"/>
    <motor gear="40"  joint="2a_left_hip_x"/>
    <motor gear="40"  joint="2a_left_hip_z"/>
    <motor gear="120" joint="2a_left_hip_y"/>
    <motor gear="80"  joint="2a_left_knee"/>
    <motor gear="20"  joint="2a_left_ankle_x"/>
    <motor gear="20"  joint="2a_left_ankle_y"/>
    <motor gear="20"  joint="2a_right_shoulder1"/>
    <motor gear="20"  joint="2a_right_shoulder2"/>
    <motor gear="40"  joint="2a_right_elbow"/>
    <motor gear="20"  joint="2a_left_shoulder1"/>
    <motor gear="20"  joint="2a_left_shoulder2"/>
    <motor gear="40"  joint="2a_left_elbow"/>
  </actuator>
  <actuator>
    <motor gear="40"  joint="3a_abdomen_y"/>
    <motor gear="40"  joint="3a_abdomen_z"/>
    <motor gear="40"  joint="3a_abdomen_x"/>
    <motor gear="40"  joint="3a_right_hip_x"/>
    <motor gear="40"  joint="3a_right_hip_z"/>
    <motor gear="120" joint="3a_right_hip_y"/>
    <motor gear="80"  joint="3a_right_knee"/>
    <motor gear="20"  joint="3a_right_ankle_x"/>
    <motor gear="20"  joint="3a_right_ankle_y"/>
    <motor gear="40"  joint="3a_left_hip_x"/>
    <motor gear="40"  joint="3a_left_hip_z"/>
    <motor gear="120" joint="3a_left_hip_y"/>
    <motor gear="80"  joint="3a_left_knee"/>
    <motor gear="20"  joint="3a_left_ankle_x"/>
    <motor gear="20"  joint="3a_left_ankle_y"/>
    <motor gear="20"  joint="3a_right_shoulder1"/>
    <motor gear="20"  joint="3a_right_shoulder2"/>
    <motor gear="40"  joint="3a_right_elbow"/>
    <motor gear="20"  joint="3a_left_shoulder1"/>
    <motor gear="20"  joint="3a_left_shoulder2"/>
    <motor gear="40"  joint="3a_left_elbow"/>
  </actuator>
  <actuator>
    <motor gear="40"  joint="4a_abdomen_y"/>
    <motor gear="40"  joint="4a_abdomen_z"/>
    <motor gear="40"  joint="4a_abdomen_x"/>
    <motor gear="40"  joint="4a_right_hip_x"/>
    <motor gear="40"  joint="4a_right_hip_z"/>
    <motor gear="120" joint="4a_right_hip_y"/>
    <motor gear="80"  joint="4a_right_knee"/>
    <motor gear="20"  joint="4a_right_ankle_x"/>
    <motor gear="20"  joint="4a_right_ankle_y"/>
    <motor gear="40"  joint="4a_left_hip_x"/>
    <motor gear="40"  joint="4a_left_hip_z"/>
    <motor gear="120" joint="4a_left_hip_y"/>
    <motor gear="80"  joint="4a_left_knee"/>
    <motor gear="20"  joint="4a_left_ankle_x"/>
    <motor gear="20"  joint="4a_left_ankle_y"/>
    <motor gear="20"  joint="4a_right_shoulder1"/>
    <motor gear="20"  joint="4a_right_shoulder2"/>
    <motor gear="40"  joint="4a_right_elbow"/>
    <motor gear="20"  joint="4a_left_shoulder1"/>
    <motor gear="20"  joint="4a_left_shoulder2"/>
    <motor gear="40"  joint="4a_left_elbow"/>
  </actuator>
 </mujoco>
@@ -0,0 +1,567 @@
 <mujoco model="05 Humanoids">
  <option timestep="0.005" solver="Newton" iterations="1" ls_iterations="4">
    <flag eulerdamp="disable"/>
  </option>
  <custom>
    <numeric data="20" name="max_contact_points"/>
    <numeric data="20" name="max_geom_pairs"/>
  </custom>
  <size memory="100M"/>
  <asset>
    <texture type="skybox" builtin="gradient" rgb1=".3 .5 .7" rgb2="0 0 0" width="512" height="512"/>
    <texture name="body" type="cube" builtin="flat" mark="cross" width="128" height="128"
             rgb1="0.8 0.6 0.4" rgb2="0.8 0.6 0.4" markrgb="1 1 1" random="0.01"/>
    <material name="body" texture="body" texuniform="true" rgba="0.8 0.6 .4 1"/>
    <texture name="grid" type="2d" builtin="checker" width="512" height="512" rgb1=".1 .2 .3" rgb2=".2 .3 .4"/>
    <material name="grid" texture="grid" texrepeat="1 1" texuniform="true" reflectance=".2"/>
  </asset>
  <default>
    <motor ctrlrange="-1 1" ctrllimited="true"/>
    <joint type="hinge" damping=".2" stiffness="1" armature=".01" limited="true" solimplimit="0 .99 .01"/>
    <default class="big_joint">
      <joint damping="5" stiffness="10"/>
      <default class="big_stiff_joint">
        <joint stiffness="20"/>
      </default>
    </default>
    <default class="body1">
      <geom type="capsule" condim="3" friction=".7" solimp=".9 .99 .003" solref=".015 1" material="body" contype="2" conaffinity="61"/>
    </default>
    <default class="body2">
      <geom type="capsule" condim="3" friction=".7" solimp=".9 .99 .003" solref=".015 1" material="body" contype="4" conaffinity="59"/>
    </default>
    <default class="body3">
      <geom type="capsule" condim="3" friction=".7" solimp=".9 .99 .003" solref=".015 1" material="body" contype="8" conaffinity="55"/>
    </default>
    <default class="body4">
      <geom type="capsule" condim="3" friction=".7" solimp=".9 .99 .003" solref=".015 1" material="body" contype="16" conaffinity="47"/>
    </default>
    <default class="body5">
      <geom type="capsule" condim="3" friction=".7" solimp=".9 .99 .003" solref=".015 1" material="body" contype="32" conaffinity="31"/>
    </default>
  </default>
  <visual>
    <map force="0.1" zfar="30"/>
    <rgba haze="0.15 0.25 0.35 1"/>
    <quality shadowsize="4096"/>
    <global offwidth="800" offheight="800"/>
  </visual>
  <worldbody>
    <geom size="10 10 .05" type="plane" material="grid" condim="3"/>
    <light dir=".2 1 -.4" diffuse=".8 .8 .8" specular="0.3 0.3 0.3" pos="-2 -10 4" cutoff="35"/>
    <light dir="-.2 1 -.4" diffuse=".8 .8 .8" specular="0.3 0.3 0.3" pos="2 -10 4" cutoff="35"/>
    <body name="1a_torso" pos="-1 0 1.5" childclass="body1">
      <camera name="1a_back" pos="-3 0 1" xyaxes="0 -1 0 1 0 2" mode="trackcom"/>
      <camera name="1a_side" pos="0 -3 1" xyaxes="1 0 0 0 1 2" mode="trackcom"/>
      <freejoint name="1a_root"/>
      <geom name="1a_torso" fromto="0 -.07 0 0 .07 0" size=".07"/>
      <geom name="1a_upper_waist" fromto="-.01 -.06 -.12 -.01 .06 -.12" size=".06"/>
      <body name="1a_head" pos="0 0 .19">
        <geom name="1a_head" type="sphere" size=".09"/>
        <camera name="1a_egocentric" pos=".09 0 0" xyaxes="0 -1 0 .1 0 1" fovy="80"/>
      </body>
      <body name="1a_lower_waist" pos="-.01 0 -.26">
        <geom name="1a_lower_waist" fromto="0 -.06 0 0 .06 0" size=".06"/>
        <joint name="1a_abdomen_z" pos="0 0 .065" axis="0 0 1" range="-45 45" class="big_stiff_joint"/>
        <joint name="1a_abdomen_y" pos="0 0 .065" axis="0 1 0" range="-75 30" class="big_joint"/>
        <body name="1a_pelvis" pos="0 0 -.165">
          <joint name="1a_abdomen_x" pos="0 0 .1" axis="1 0 0" range="-35 35" class="big_joint"/>
          <geom name="1a_butt" fromto="-.02 -.07 0 -.02 .07 0" size=".09"/>
          <body name="1a_right_thigh" pos="0 -.1 -.04">
            <joint name="1a_right_hip_x" axis="1 0 0" range="-25 5" class="big_joint"/>
            <joint name="1a_right_hip_z" axis="0 0 1" range="-60 35" class="big_joint"/>
            <joint name="1a_right_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="1a_right_thigh" fromto="0 0 0 0 .01 -.34" size=".06"/>
            <body name="1a_right_shin" pos="0 .01 -.403">
              <joint name="1a_right_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="1a_right_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="1a_right_foot" pos="0 0 -.39">
                <joint name="1a_right_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="1a_right_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="1a_right_right_foot" fromto="-.07 -.02 0 .14 -.04 0" size=".027"/>
                <geom name="1a_left_right_foot" fromto="-.07 0 0 .14  .02 0" size=".027"/>
              </body>
            </body>
          </body>
          <body name="1a_left_thigh" pos="0 .1 -.04">
            <joint name="1a_left_hip_x" axis="-1 0 0" range="-25 5" class="big_joint"/>
            <joint name="1a_left_hip_z" axis="0 0 -1" range="-60 35" class="big_joint"/>
            <joint name="1a_left_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="1a_left_thigh" fromto="0 0 0 0 -.01 -.34" size=".06"/>
            <body name="1a_left_shin" pos="0 -.01 -.403">
              <joint name="1a_left_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="1a_left_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="1a_left_foot" pos="0 0 -.39">
                <joint name="1a_left_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="1a_left_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="1a_left_left_foot" fromto="-.07 .02 0 .14 .04 0" size=".027"/>
                <geom name="1a_right_left_foot" fromto="-.07 0 0 .14 -.02 0" size=".027"/>
              </body>
            </body>
          </body>
        </body>
      </body>
      <body name="1a_right_upper_arm" pos="0 -.17 .06">
        <joint name="1a_right_shoulder1" axis="2 1 1"  range="-85 60"/>
        <joint name="1a_right_shoulder2" axis="0 -1 1" range="-85 60"/>
        <geom name="1a_right_upper_arm" fromto="0 0 0 .16 -.16 -.16" size=".04 .16"/>
        <body name="1a_right_lower_arm" pos=".18 -.18 -.18">
          <joint name="1a_right_elbow" axis="0 -1 1" range="-90 50" stiffness="0"/>
          <geom name="1a_right_lower_arm" fromto=".01 .01 .01 .17 .17 .17" size=".031"/>
          <body name="1a_right_hand" pos=".18 .18 .18">
            <geom name="1a_right_hand" type="sphere" size=".04" zaxis="1 1 1"/>
          </body>
        </body>
      </body>
      <body name="1a_left_upper_arm" pos="0 .17 .06">
        <joint name="1a_left_shoulder1" axis="2 -1 1" range="-60 85"/>
        <joint name="1a_left_shoulder2" axis="0 1 1"  range="-60 85"/>
        <geom name="1a_left_upper_arm" fromto="0 0 0 .16 .16 -.16" size=".04 .16"/>
        <body name="1a_left_lower_arm" pos=".18 .18 -.18">
          <joint name="1a_left_elbow" axis="0 -1 -1" range="-90 50" stiffness="0"/>
          <geom name="1a_left_lower_arm" fromto=".01 -.01 .01 .17 -.17 .17" size=".031"/>
          <body name="1a_left_hand" pos=".18 -.18 .18">
            <geom name="1a_left_hand" type="sphere" size=".04" zaxis="1 -1 1"/>
          </body>
        </body>
      </body>
    </body>
    <body name="2a_torso" pos="-1 1 1.5" childclass="body2">
      <camera name="2a_back" pos="-3 0 1" xyaxes="0 -1 0 1 0 2" mode="trackcom"/>
      <camera name="2a_side" pos="0 -3 1" xyaxes="1 0 0 0 1 2" mode="trackcom"/>
      <freejoint name="2a_root"/>
      <geom name="2a_torso" fromto="0 -.07 0 0 .07 0" size=".07"/>
      <geom name="2a_upper_waist" fromto="-.01 -.06 -.12 -.01 .06 -.12" size=".06"/>
      <body name="2a_head" pos="0 0 .19">
        <geom name="2a_head" type="sphere" size=".09"/>
        <camera name="2a_egocentric" pos=".09 0 0" xyaxes="0 -1 0 .1 0 1" fovy="80"/>
      </body>
      <body name="2a_lower_waist" pos="-.01 0 -.26">
        <geom name="2a_lower_waist" fromto="0 -.06 0 0 .06 0" size=".06"/>
        <joint name="2a_abdomen_z" pos="0 0 .065" axis="0 0 1" range="-45 45" class="big_stiff_joint"/>
        <joint name="2a_abdomen_y" pos="0 0 .065" axis="0 1 0" range="-75 30" class="big_joint"/>
        <body name="2a_pelvis" pos="0 0 -.165">
          <joint name="2a_abdomen_x" pos="0 0 .1" axis="1 0 0" range="-35 35" class="big_joint"/>
          <geom name="2a_butt" fromto="-.02 -.07 0 -.02 .07 0" size=".09"/>
          <body name="2a_right_thigh" pos="0 -.1 -.04">
            <joint name="2a_right_hip_x" axis="1 0 0" range="-25 5" class="big_joint"/>
            <joint name="2a_right_hip_z" axis="0 0 1" range="-60 35" class="big_joint"/>
            <joint name="2a_right_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="2a_right_thigh" fromto="0 0 0 0 .01 -.34" size=".06"/>
            <body name="2a_right_shin" pos="0 .01 -.403">
              <joint name="2a_right_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="2a_right_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="2a_right_foot" pos="0 0 -.39">
                <joint name="2a_right_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="2a_right_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="2a_right_right_foot" fromto="-.07 -.02 0 .14 -.04 0" size=".027"/>
                <geom name="2a_left_right_foot" fromto="-.07 0 0 .14  .02 0" size=".027"/>
              </body>
            </body>
          </body>
          <body name="2a_left_thigh" pos="0 .1 -.04">
            <joint name="2a_left_hip_x" axis="-1 0 0" range="-25 5" class="big_joint"/>
            <joint name="2a_left_hip_z" axis="0 0 -1" range="-60 35" class="big_joint"/>
            <joint name="2a_left_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="2a_left_thigh" fromto="0 0 0 0 -.01 -.34" size=".06"/>
            <body name="2a_left_shin" pos="0 -.01 -.403">
              <joint name="2a_left_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="2a_left_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="2a_left_foot" pos="0 0 -.39">
                <joint name="2a_left_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="2a_left_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="2a_left_left_foot" fromto="-.07 .02 0 .14 .04 0" size=".027"/>
                <geom name="2a_right_left_foot" fromto="-.07 0 0 .14 -.02 0" size=".027"/>
              </body>
            </body>
          </body>
        </body>
      </body>
      <body name="2a_right_upper_arm" pos="0 -.17 .06">
        <joint name="2a_right_shoulder1" axis="2 1 1"  range="-85 60"/>
        <joint name="2a_right_shoulder2" axis="0 -1 1" range="-85 60"/>
        <geom name="2a_right_upper_arm" fromto="0 0 0 .16 -.16 -.16" size=".04 .16"/>
        <body name="2a_right_lower_arm" pos=".18 -.18 -.18">
          <joint name="2a_right_elbow" axis="0 -1 1" range="-90 50" stiffness="0"/>
          <geom name="2a_right_lower_arm" fromto=".01 .01 .01 .17 .17 .17" size=".031"/>
          <body name="2a_right_hand" pos=".18 .18 .18">
            <geom name="2a_right_hand" type="sphere" size=".04" zaxis="1 1 1"/>
          </body>
        </body>
      </body>
      <body name="2a_left_upper_arm" pos="0 .17 .06">
        <joint name="2a_left_shoulder1" axis="2 -1 1" range="-60 85"/>
        <joint name="2a_left_shoulder2" axis="0 1 1"  range="-60 85"/>
        <geom name="2a_left_upper_arm" fromto="0 0 0 .16 .16 -.16" size=".04 .16"/>
        <body name="2a_left_lower_arm" pos=".18 .18 -.18">
          <joint name="2a_left_elbow" axis="0 -1 -1" range="-90 50" stiffness="0"/>
          <geom name="2a_left_lower_arm" fromto=".01 -.01 .01 .17 -.17 .17" size=".031"/>
          <body name="2a_left_hand" pos=".18 -.18 .18">
            <geom name="2a_left_hand" type="sphere" size=".04" zaxis="1 -1 1"/>
          </body>
        </body>
      </body>
    </body>
    <body name="3a_torso" pos="-1 -1 1.5" childclass="body3">
      <camera name="3a_back" pos="-3 0 1" xyaxes="0 -1 0 1 0 2" mode="trackcom"/>
      <camera name="3a_side" pos="0 -3 1" xyaxes="1 0 0 0 1 2" mode="trackcom"/>
      <freejoint name="3a_root"/>
      <geom name="3a_torso" fromto="0 -.07 0 0 .07 0" size=".07"/>
      <geom name="3a_upper_waist" fromto="-.01 -.06 -.12 -.01 .06 -.12" size=".06"/>
      <body name="3a_head" pos="0 0 .19">
        <geom name="3a_head" type="sphere" size=".09"/>
        <camera name="3a_egocentric" pos=".09 0 0" xyaxes="0 -1 0 .1 0 1" fovy="80"/>
      </body>
      <body name="3a_lower_waist" pos="-.01 0 -.26">
        <geom name="3a_lower_waist" fromto="0 -.06 0 0 .06 0" size=".06"/>
        <joint name="3a_abdomen_z" pos="0 0 .065" axis="0 0 1" range="-45 45" class="big_stiff_joint"/>
        <joint name="3a_abdomen_y" pos="0 0 .065" axis="0 1 0" range="-75 30" class="big_joint"/>
        <body name="3a_pelvis" pos="0 0 -.165">
          <joint name="3a_abdomen_x" pos="0 0 .1" axis="1 0 0" range="-35 35" class="big_joint"/>
          <geom name="3a_butt" fromto="-.02 -.07 0 -.02 .07 0" size=".09"/>
          <body name="3a_right_thigh" pos="0 -.1 -.04">
            <joint name="3a_right_hip_x" axis="1 0 0" range="-25 5" class="big_joint"/>
            <joint name="3a_right_hip_z" axis="0 0 1" range="-60 35" class="big_joint"/>
            <joint name="3a_right_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="3a_right_thigh" fromto="0 0 0 0 .01 -.34" size=".06"/>
            <body name="3a_right_shin" pos="0 .01 -.403">
              <joint name="3a_right_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="3a_right_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="3a_right_foot" pos="0 0 -.39">
                <joint name="3a_right_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="3a_right_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="3a_right_right_foot" fromto="-.07 -.02 0 .14 -.04 0" size=".027"/>
                <geom name="3a_left_right_foot" fromto="-.07 0 0 .14  .02 0" size=".027"/>
              </body>
            </body>
          </body>
          <body name="3a_left_thigh" pos="0 .1 -.04">
            <joint name="3a_left_hip_x" axis="-1 0 0" range="-25 5" class="big_joint"/>
            <joint name="3a_left_hip_z" axis="0 0 -1" range="-60 35" class="big_joint"/>
            <joint name="3a_left_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="3a_left_thigh" fromto="0 0 0 0 -.01 -.34" size=".06"/>
            <body name="3a_left_shin" pos="0 -.01 -.403">
              <joint name="3a_left_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="3a_left_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="3a_left_foot" pos="0 0 -.39">
                <joint name="3a_left_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="3a_left_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="3a_left_left_foot" fromto="-.07 .02 0 .14 .04 0" size=".027"/>
                <geom name="3a_right_left_foot" fromto="-.07 0 0 .14 -.02 0" size=".027"/>
              </body>
            </body>
          </body>
        </body>
      </body>
      <body name="3a_right_upper_arm" pos="0 -.17 .06">
        <joint name="3a_right_shoulder1" axis="2 1 1"  range="-85 60"/>
        <joint name="3a_right_shoulder2" axis="0 -1 1" range="-85 60"/>
        <geom name="3a_right_upper_arm" fromto="0 0 0 .16 -.16 -.16" size=".04 .16"/>
        <body name="3a_right_lower_arm" pos=".18 -.18 -.18">
          <joint name="3a_right_elbow" axis="0 -1 1" range="-90 50" stiffness="0"/>
          <geom name="3a_right_lower_arm" fromto=".01 .01 .01 .17 .17 .17" size=".031"/>
          <body name="3a_right_hand" pos=".18 .18 .18">
            <geom name="3a_right_hand" type="sphere" size=".04" zaxis="1 1 1"/>
          </body>
        </body>
      </body>
      <body name="3a_left_upper_arm" pos="0 .17 .06">
        <joint name="3a_left_shoulder1" axis="2 -1 1" range="-60 85"/>
        <joint name="3a_left_shoulder2" axis="0 1 1"  range="-60 85"/>
        <geom name="3a_left_upper_arm" fromto="0 0 0 .16 .16 -.16" size=".04 .16"/>
        <body name="3a_left_lower_arm" pos=".18 .18 -.18">
          <joint name="3a_left_elbow" axis="0 -1 -1" range="-90 50" stiffness="0"/>
          <geom name="3a_left_lower_arm" fromto=".01 -.01 .01 .17 -.17 .17" size=".031"/>
          <body name="3a_left_hand" pos=".18 -.18 .18">
            <geom name="3a_left_hand" type="sphere" size=".04" zaxis="1 -1 1"/>
          </body>
        </body>
      </body>
    </body>
    <body name="4a_torso" pos="-1 2 1.5" childclass="body4">
      <camera name="4a_back" pos="-3 0 1" xyaxes="0 -1 0 1 0 2" mode="trackcom"/>
      <camera name="4a_side" pos="0 -3 1" xyaxes="1 0 0 0 1 2" mode="trackcom"/>
      <freejoint name="4a_root"/>
      <geom name="4a_torso" fromto="0 -.07 0 0 .07 0" size=".07"/>
      <geom name="4a_upper_waist" fromto="-.01 -.06 -.12 -.01 .06 -.12" size=".06"/>
      <body name="4a_head" pos="0 0 .19">
        <geom name="4a_head" type="sphere" size=".09"/>
        <camera name="4a_egocentric" pos=".09 0 0" xyaxes="0 -1 0 .1 0 1" fovy="80"/>
      </body>
      <body name="4a_lower_waist" pos="-.01 0 -.26">
        <geom name="4a_lower_waist" fromto="0 -.06 0 0 .06 0" size=".06"/>
        <joint name="4a_abdomen_z" pos="0 0 .065" axis="0 0 1" range="-45 45" class="big_stiff_joint"/>
        <joint name="4a_abdomen_y" pos="0 0 .065" axis="0 1 0" range="-75 30" class="big_joint"/>
        <body name="4a_pelvis" pos="0 0 -.165">
          <joint name="4a_abdomen_x" pos="0 0 .1" axis="1 0 0" range="-35 35" class="big_joint"/>
          <geom name="4a_butt" fromto="-.02 -.07 0 -.02 .07 0" size=".09"/>
          <body name="4a_right_thigh" pos="0 -.1 -.04">
            <joint name="4a_right_hip_x" axis="1 0 0" range="-25 5" class="big_joint"/>
            <joint name="4a_right_hip_z" axis="0 0 1" range="-60 35" class="big_joint"/>
            <joint name="4a_right_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="4a_right_thigh" fromto="0 0 0 0 .01 -.34" size=".06"/>
            <body name="4a_right_shin" pos="0 .01 -.403">
              <joint name="4a_right_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="4a_right_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="4a_right_foot" pos="0 0 -.39">
                <joint name="4a_right_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="4a_right_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="4a_right_right_foot" fromto="-.07 -.02 0 .14 -.04 0" size=".027"/>
                <geom name="4a_left_right_foot" fromto="-.07 0 0 .14  .02 0" size=".027"/>
              </body>
            </body>
          </body>
          <body name="4a_left_thigh" pos="0 .1 -.04">
            <joint name="4a_left_hip_x" axis="-1 0 0" range="-25 5" class="big_joint"/>
            <joint name="4a_left_hip_z" axis="0 0 -1" range="-60 35" class="big_joint"/>
            <joint name="4a_left_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="4a_left_thigh" fromto="0 0 0 0 -.01 -.34" size=".06"/>
            <body name="4a_left_shin" pos="0 -.01 -.403">
              <joint name="4a_left_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="4a_left_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="4a_left_foot" pos="0 0 -.39">
                <joint name="4a_left_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="4a_left_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="4a_left_left_foot" fromto="-.07 .02 0 .14 .04 0" size=".027"/>
                <geom name="4a_right_left_foot" fromto="-.07 0 0 .14 -.02 0" size=".027"/>
              </body>
            </body>
          </body>
        </body>
      </body>
      <body name="4a_right_upper_arm" pos="0 -.17 .06">
        <joint name="4a_right_shoulder1" axis="2 1 1"  range="-85 60"/>
        <joint name="4a_right_shoulder2" axis="0 -1 1" range="-85 60"/>
        <geom name="4a_right_upper_arm" fromto="0 0 0 .16 -.16 -.16" size=".04 .16"/>
        <body name="4a_right_lower_arm" pos=".18 -.18 -.18">
          <joint name="4a_right_elbow" axis="0 -1 1" range="-90 50" stiffness="0"/>
          <geom name="4a_right_lower_arm" fromto=".01 .01 .01 .17 .17 .17" size=".031"/>
          <body name="4a_right_hand" pos=".18 .18 .18">
            <geom name="4a_right_hand" type="sphere" size=".04" zaxis="1 1 1"/>
          </body>
        </body>
      </body>
      <body name="4a_left_upper_arm" pos="0 .17 .06">
        <joint name="4a_left_shoulder1" axis="2 -1 1" range="-60 85"/>
        <joint name="4a_left_shoulder2" axis="0 1 1"  range="-60 85"/>
        <geom name="4a_left_upper_arm" fromto="0 0 0 .16 .16 -.16" size=".04 .16"/>
        <body name="4a_left_lower_arm" pos=".18 .18 -.18">
          <joint name="4a_left_elbow" axis="0 -1 -1" range="-90 50" stiffness="0"/>
          <geom name="4a_left_lower_arm" fromto=".01 -.01 .01 .17 -.17 .17" size=".031"/>
          <body name="4a_left_hand" pos=".18 -.18 .18">
            <geom name="4a_left_hand" type="sphere" size=".04" zaxis="1 -1 1"/>
          </body>
        </body>
      </body>
    </body>
    <body name="5a_torso" pos="-1 -2 1.5" childclass="body5">
      <camera name="5a_back" pos="-3 0 1" xyaxes="0 -1 0 1 0 2" mode="trackcom"/>
      <camera name="5a_side" pos="0 -3 1" xyaxes="1 0 0 0 1 2" mode="trackcom"/>
      <freejoint name="5a_root"/>
      <geom name="5a_torso" fromto="0 -.07 0 0 .07 0" size=".07"/>
      <geom name="5a_upper_waist" fromto="-.01 -.06 -.12 -.01 .06 -.12" size=".06"/>
      <body name="5a_head" pos="0 0 .19">
        <geom name="5a_head" type="sphere" size=".09"/>
        <camera name="5a_egocentric" pos=".09 0 0" xyaxes="0 -1 0 .1 0 1" fovy="80"/>
      </body>
      <body name="5a_lower_waist" pos="-.01 0 -.26">
        <geom name="5a_lower_waist" fromto="0 -.06 0 0 .06 0" size=".06"/>
        <joint name="5a_abdomen_z" pos="0 0 .065" axis="0 0 1" range="-45 45" class="big_stiff_joint"/>
        <joint name="5a_abdomen_y" pos="0 0 .065" axis="0 1 0" range="-75 30" class="big_joint"/>
        <body name="5a_pelvis" pos="0 0 -.165">
          <joint name="5a_abdomen_x" pos="0 0 .1" axis="1 0 0" range="-35 35" class="big_joint"/>
          <geom name="5a_butt" fromto="-.02 -.07 0 -.02 .07 0" size=".09"/>
          <body name="5a_right_thigh" pos="0 -.1 -.04">
            <joint name="5a_right_hip_x" axis="1 0 0" range="-25 5" class="big_joint"/>
            <joint name="5a_right_hip_z" axis="0 0 1" range="-60 35" class="big_joint"/>
            <joint name="5a_right_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="5a_right_thigh" fromto="0 0 0 0 .01 -.34" size=".06"/>
            <body name="5a_right_shin" pos="0 .01 -.403">
              <joint name="5a_right_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="5a_right_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="5a_right_foot" pos="0 0 -.39">
                <joint name="5a_right_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="5a_right_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="5a_right_right_foot" fromto="-.07 -.02 0 .14 -.04 0" size=".027"/>
                <geom name="5a_left_right_foot" fromto="-.07 0 0 .14  .02 0" size=".027"/>
              </body>
            </body>
          </body>
          <body name="5a_left_thigh" pos="0 .1 -.04">
            <joint name="5a_left_hip_x" axis="-1 0 0" range="-25 5" class="big_joint"/>
            <joint name="5a_left_hip_z" axis="0 0 -1" range="-60 35" class="big_joint"/>
            <joint name="5a_left_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="5a_left_thigh" fromto="0 0 0 0 -.01 -.34" size=".06"/>
            <body name="5a_left_shin" pos="0 -.01 -.403">
              <joint name="5a_left_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="5a_left_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="5a_left_foot" pos="0 0 -.39">
                <joint name="5a_left_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="5a_left_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="5a_left_left_foot" fromto="-.07 .02 0 .14 .04 0" size=".027"/>
                <geom name="5a_right_left_foot" fromto="-.07 0 0 .14 -.02 0" size=".027"/>
              </body>
            </body>
          </body>
        </body>
      </body>
      <body name="5a_right_upper_arm" pos="0 -.17 .06">
        <joint name="5a_right_shoulder1" axis="2 1 1"  range="-85 60"/>
        <joint name="5a_right_shoulder2" axis="0 -1 1" range="-85 60"/>
        <geom name="5a_right_upper_arm" fromto="0 0 0 .16 -.16 -.16" size=".04 .16"/>
        <body name="5a_right_lower_arm" pos=".18 -.18 -.18">
          <joint name="5a_right_elbow" axis="0 -1 1" range="-90 50" stiffness="0"/>
          <geom name="5a_right_lower_arm" fromto=".01 .01 .01 .17 .17 .17" size=".031"/>
          <body name="5a_right_hand" pos=".18 .18 .18">
            <geom name="5a_right_hand" type="sphere" size=".04" zaxis="1 1 1"/>
          </body>
        </body>
      </body>
      <body name="5a_left_upper_arm" pos="0 .17 .06">
        <joint name="5a_left_shoulder1" axis="2 -1 1" range="-60 85"/>
        <joint name="5a_left_shoulder2" axis="0 1 1"  range="-60 85"/>
        <geom name="5a_left_upper_arm" fromto="0 0 0 .16 .16 -.16" size=".04 .16"/>
        <body name="5a_left_lower_arm" pos=".18 .18 -.18">
          <joint name="5a_left_elbow" axis="0 -1 -1" range="-90 50" stiffness="0"/>
          <geom name="5a_left_lower_arm" fromto=".01 -.01 .01 .17 -.17 .17" size=".031"/>
          <body name="5a_left_hand" pos=".18 -.18 .18">
            <geom name="5a_left_hand" type="sphere" size=".04" zaxis="1 -1 1"/>
          </body>
        </body>
      </body>
    </body>
  </worldbody>
  <actuator>
    <motor gear="40"  joint="1a_abdomen_y"/>
    <motor gear="40"  joint="1a_abdomen_z"/>
    <motor gear="40"  joint="1a_abdomen_x"/>
    <motor gear="40"  joint="1a_right_hip_x"/>
    <motor gear="40"  joint="1a_right_hip_z"/>
    <motor gear="120" joint="1a_right_hip_y"/>
    <motor gear="80"  joint="1a_right_knee"/>
    <motor gear="20"  joint="1a_right_ankle_x"/>
    <motor gear="20"  joint="1a_right_ankle_y"/>
    <motor gear="40"  joint="1a_left_hip_x"/>
    <motor gear="40"  joint="1a_left_hip_z"/>
    <motor gear="120" joint="1a_left_hip_y"/>
    <motor gear="80"  joint="1a_left_knee"/>
    <motor gear="20"  joint="1a_left_ankle_x"/>
    <motor gear="20"  joint="1a_left_ankle_y"/>
    <motor gear="20"  joint="1a_right_shoulder1"/>
    <motor gear="20"  joint="1a_right_shoulder2"/>
    <motor gear="40"  joint="1a_right_elbow"/>
    <motor gear="20"  joint="1a_left_shoulder1"/>
    <motor gear="20"  joint="1a_left_shoulder2"/>
    <motor gear="40"  joint="1a_left_elbow"/>
  </actuator>
  <actuator>
    <motor gear="40"  joint="2a_abdomen_y"/>
    <motor gear="40"  joint="2a_abdomen_z"/>
    <motor gear="40"  joint="2a_abdomen_x"/>
    <motor gear="40"  joint="2a_right_hip_x"/>
    <motor gear="40"  joint="2a_right_hip_z"/>
    <motor gear="120" joint="2a_right_hip_y"/>
    <motor gear="80"  joint="2a_right_knee"/>
    <motor gear="20"  joint="2a_right_ankle_x"/>
    <motor gear="20"  joint="2a_right_ankle_y"/>
    <motor gear="40"  joint="2a_left_hip_x"/>
    <motor gear="40"  joint="2a_left_hip_z"/>
    <motor gear="120" joint="2a_left_hip_y"/>
    <motor gear="80"  joint="2a_left_knee"/>
    <motor gear="20"  joint="2a_left_ankle_x"/>
    <motor gear="20"  joint="2a_left_ankle_y"/>
    <motor gear="20"  joint="2a_right_shoulder1"/>
    <motor gear="20"  joint="2a_right_shoulder2"/>
    <motor gear="40"  joint="2a_right_elbow"/>
    <motor gear="20"  joint="2a_left_shoulder1"/>
    <motor gear="20"  joint="2a_left_shoulder2"/>
    <motor gear="40"  joint="2a_left_elbow"/>
  </actuator>
  <actuator>
    <motor gear="40"  joint="3a_abdomen_y"/>
    <motor gear="40"  joint="3a_abdomen_z"/>
    <motor gear="40"  joint="3a_abdomen_x"/>
    <motor gear="40"  joint="3a_right_hip_x"/>
    <motor gear="40"  joint="3a_right_hip_z"/>
    <motor gear="120" joint="3a_right_hip_y"/>
    <motor gear="80"  joint="3a_right_knee"/>
    <motor gear="20"  joint="3a_right_ankle_x"/>
    <motor gear="20"  joint="3a_right_ankle_y"/>
    <motor gear="40"  joint="3a_left_hip_x"/>
    <motor gear="40"  joint="3a_left_hip_z"/>
    <motor gear="120" joint="3a_left_hip_y"/>
    <motor gear="80"  joint="3a_left_knee"/>
    <motor gear="20"  joint="3a_left_ankle_x"/>
    <motor gear="20"  joint="3a_left_ankle_y"/>
    <motor gear="20"  joint="3a_right_shoulder1"/>
    <motor gear="20"  joint="3a_right_shoulder2"/>
    <motor gear="40"  joint="3a_right_elbow"/>
    <motor gear="20"  joint="3a_left_shoulder1"/>
    <motor gear="20"  joint="3a_left_shoulder2"/>
    <motor gear="40"  joint="3a_left_elbow"/>
  </actuator>
  <actuator>
    <motor gear="40"  joint="4a_abdomen_y"/>
    <motor gear="40"  joint="4a_abdomen_z"/>
    <motor gear="40"  joint="4a_abdomen_x"/>
    <motor gear="40"  joint="4a_right_hip_x"/>
    <motor gear="40"  joint="4a_right_hip_z"/>
    <motor gear="120" joint="4a_right_hip_y"/>
    <motor gear="80"  joint="4a_right_knee"/>
    <motor gear="20"  joint="4a_right_ankle_x"/>
    <motor gear="20"  joint="4a_right_ankle_y"/>
    <motor gear="40"  joint="4a_left_hip_x"/>
    <motor gear="40"  joint="4a_left_hip_z"/>
    <motor gear="120" joint="4a_left_hip_y"/>
    <motor gear="80"  joint="4a_left_knee"/>
    <motor gear="20"  joint="4a_left_ankle_x"/>
    <motor gear="20"  joint="4a_left_ankle_y"/>
    <motor gear="20"  joint="4a_right_shoulder1"/>
    <motor gear="20"  joint="4a_right_shoulder2"/>
    <motor gear="40"  joint="4a_right_elbow"/>
    <motor gear="20"  joint="4a_left_shoulder1"/>
    <motor gear="20"  joint="4a_left_shoulder2"/>
    <motor gear="40"  joint="4a_left_elbow"/>
  </actuator>
  <actuator>
    <motor gear="40"  joint="5a_abdomen_y"/>
    <motor gear="40"  joint="5a_abdomen_z"/>
    <motor gear="40"  joint="5a_abdomen_x"/>
    <motor gear="40"  joint="5a_right_hip_x"/>
    <motor gear="40"  joint="5a_right_hip_z"/>
    <motor gear="120" joint="5a_right_hip_y"/>
    <motor gear="80"  joint="5a_right_knee"/>
    <motor gear="20"  joint="5a_right_ankle_x"/>
    <motor gear="20"  joint="5a_right_ankle_y"/>
    <motor gear="40"  joint="5a_left_hip_x"/>
    <motor gear="40"  joint="5a_left_hip_z"/>
    <motor gear="120" joint="5a_left_hip_y"/>
    <motor gear="80"  joint="5a_left_knee"/>
    <motor gear="20"  joint="5a_left_ankle_x"/>
    <motor gear="20"  joint="5a_left_ankle_y"/>
    <motor gear="20"  joint="5a_right_shoulder1"/>
    <motor gear="20"  joint="5a_right_shoulder2"/>
    <motor gear="40"  joint="5a_right_elbow"/>
    <motor gear="20"  joint="5a_left_shoulder1"/>
    <motor gear="20"  joint="5a_left_shoulder2"/>
    <motor gear="40"  joint="5a_left_elbow"/>
  </actuator>
 </mujoco>
@@ -0,0 +1,671 @@
 <mujoco model="06 Humanoids">
  <option timestep="0.005" solver="Newton" iterations="1" ls_iterations="4">
    <flag eulerdamp="disable"/>
  </option>
  <custom>
    <numeric data="24" name="max_contact_points"/>
    <numeric data="24" name="max_geom_pairs"/>
  </custom>
  <size memory="100M"/>
  <asset>
    <texture type="skybox" builtin="gradient" rgb1=".3 .5 .7" rgb2="0 0 0" width="512" height="512"/>
    <texture name="body" type="cube" builtin="flat" mark="cross" width="128" height="128"
             rgb1="0.8 0.6 0.4" rgb2="0.8 0.6 0.4" markrgb="1 1 1" random="0.01"/>
    <material name="body" texture="body" texuniform="true" rgba="0.8 0.6 .4 1"/>
    <texture name="grid" type="2d" builtin="checker" width="512" height="512" rgb1=".1 .2 .3" rgb2=".2 .3 .4"/>
    <material name="grid" texture="grid" texrepeat="1 1" texuniform="true" reflectance=".2"/>
  </asset>
  <default>
    <motor ctrlrange="-1 1" ctrllimited="true"/>
    <joint type="hinge" damping=".2" stiffness="1" armature=".01" limited="true" solimplimit="0 .99 .01"/>
    <default class="big_joint">
      <joint damping="5" stiffness="10"/>
      <default class="big_stiff_joint">
        <joint stiffness="20"/>
      </default>
    </default>
    <default class="body1">
      <geom type="capsule" condim="3" friction=".7" solimp=".9 .99 .003" solref=".015 1" material="body" contype="2" conaffinity="125"/>
    </default>
    <default class="body2">
      <geom type="capsule" condim="3" friction=".7" solimp=".9 .99 .003" solref=".015 1" material="body" contype="4" conaffinity="123"/>
    </default>
    <default class="body3">
      <geom type="capsule" condim="3" friction=".7" solimp=".9 .99 .003" solref=".015 1" material="body" contype="8" conaffinity="119"/>
    </default>
    <default class="body4">
      <geom type="capsule" condim="3" friction=".7" solimp=".9 .99 .003" solref=".015 1" material="body" contype="16" conaffinity="111"/>
    </default>
    <default class="body5">
      <geom type="capsule" condim="3" friction=".7" solimp=".9 .99 .003" solref=".015 1" material="body" contype="32" conaffinity="95"/>
    </default>
    <default class="body6">
      <geom type="capsule" condim="3" friction=".7" solimp=".9 .99 .003" solref=".015 1" material="body" contype="64" conaffinity="63"/>
    </default>
  </default>
  <visual>
    <map force="0.1" zfar="30"/>
    <rgba haze="0.15 0.25 0.35 1"/>
    <quality shadowsize="4096"/>
    <global offwidth="800" offheight="800"/>
  </visual>
  <worldbody>
    <geom size="10 10 .05" type="plane" material="grid" condim="3"/>
    <light dir=".2 1 -.4" diffuse=".8 .8 .8" specular="0.3 0.3 0.3" pos="-2 -10 4" cutoff="35"/>
    <light dir="-.2 1 -.4" diffuse=".8 .8 .8" specular="0.3 0.3 0.3" pos="2 -10 4" cutoff="35"/>
    <body name="1a_torso" pos="-1 0 1.5" childclass="body1">
      <camera name="1a_back" pos="-3 0 1" xyaxes="0 -1 0 1 0 2" mode="trackcom"/>
      <camera name="1a_side" pos="0 -3 1" xyaxes="1 0 0 0 1 2" mode="trackcom"/>
      <freejoint name="1a_root"/>
      <geom name="1a_torso" fromto="0 -.07 0 0 .07 0" size=".07"/>
      <geom name="1a_upper_waist" fromto="-.01 -.06 -.12 -.01 .06 -.12" size=".06"/>
      <body name="1a_head" pos="0 0 .19">
        <geom name="1a_head" type="sphere" size=".09"/>
        <camera name="1a_egocentric" pos=".09 0 0" xyaxes="0 -1 0 .1 0 1" fovy="80"/>
      </body>
      <body name="1a_lower_waist" pos="-.01 0 -.26">
        <geom name="1a_lower_waist" fromto="0 -.06 0 0 .06 0" size=".06"/>
        <joint name="1a_abdomen_z" pos="0 0 .065" axis="0 0 1" range="-45 45" class="big_stiff_joint"/>
        <joint name="1a_abdomen_y" pos="0 0 .065" axis="0 1 0" range="-75 30" class="big_joint"/>
        <body name="1a_pelvis" pos="0 0 -.165">
          <joint name="1a_abdomen_x" pos="0 0 .1" axis="1 0 0" range="-35 35" class="big_joint"/>
          <geom name="1a_butt" fromto="-.02 -.07 0 -.02 .07 0" size=".09"/>
          <body name="1a_right_thigh" pos="0 -.1 -.04">
            <joint name="1a_right_hip_x" axis="1 0 0" range="-25 5" class="big_joint"/>
            <joint name="1a_right_hip_z" axis="0 0 1" range="-60 35" class="big_joint"/>
            <joint name="1a_right_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="1a_right_thigh" fromto="0 0 0 0 .01 -.34" size=".06"/>
            <body name="1a_right_shin" pos="0 .01 -.403">
              <joint name="1a_right_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="1a_right_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="1a_right_foot" pos="0 0 -.39">
                <joint name="1a_right_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="1a_right_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="1a_right_right_foot" fromto="-.07 -.02 0 .14 -.04 0" size=".027"/>
                <geom name="1a_left_right_foot" fromto="-.07 0 0 .14  .02 0" size=".027"/>
              </body>
            </body>
          </body>
          <body name="1a_left_thigh" pos="0 .1 -.04">
            <joint name="1a_left_hip_x" axis="-1 0 0" range="-25 5" class="big_joint"/>
            <joint name="1a_left_hip_z" axis="0 0 -1" range="-60 35" class="big_joint"/>
            <joint name="1a_left_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="1a_left_thigh" fromto="0 0 0 0 -.01 -.34" size=".06"/>
            <body name="1a_left_shin" pos="0 -.01 -.403">
              <joint name="1a_left_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="1a_left_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="1a_left_foot" pos="0 0 -.39">
                <joint name="1a_left_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="1a_left_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="1a_left_left_foot" fromto="-.07 .02 0 .14 .04 0" size=".027"/>
                <geom name="1a_right_left_foot" fromto="-.07 0 0 .14 -.02 0" size=".027"/>
              </body>
            </body>
          </body>
        </body>
      </body>
      <body name="1a_right_upper_arm" pos="0 -.17 .06">
        <joint name="1a_right_shoulder1" axis="2 1 1"  range="-85 60"/>
        <joint name="1a_right_shoulder2" axis="0 -1 1" range="-85 60"/>
        <geom name="1a_right_upper_arm" fromto="0 0 0 .16 -.16 -.16" size=".04 .16"/>
        <body name="1a_right_lower_arm" pos=".18 -.18 -.18">
          <joint name="1a_right_elbow" axis="0 -1 1" range="-90 50" stiffness="0"/>
          <geom name="1a_right_lower_arm" fromto=".01 .01 .01 .17 .17 .17" size=".031"/>
          <body name="1a_right_hand" pos=".18 .18 .18">
            <geom name="1a_right_hand" type="sphere" size=".04" zaxis="1 1 1"/>
          </body>
        </body>
      </body>
      <body name="1a_left_upper_arm" pos="0 .17 .06">
        <joint name="1a_left_shoulder1" axis="2 -1 1" range="-60 85"/>
        <joint name="1a_left_shoulder2" axis="0 1 1"  range="-60 85"/>
        <geom name="1a_left_upper_arm" fromto="0 0 0 .16 .16 -.16" size=".04 .16"/>
        <body name="1a_left_lower_arm" pos=".18 .18 -.18">
          <joint name="1a_left_elbow" axis="0 -1 -1" range="-90 50" stiffness="0"/>
          <geom name="1a_left_lower_arm" fromto=".01 -.01 .01 .17 -.17 .17" size=".031"/>
          <body name="1a_left_hand" pos=".18 -.18 .18">
            <geom name="1a_left_hand" type="sphere" size=".04" zaxis="1 -1 1"/>
          </body>
        </body>
      </body>
    </body>
    <body name="2a_torso" pos="-1 1 1.5" childclass="body2">
      <camera name="2a_back" pos="-3 0 1" xyaxes="0 -1 0 1 0 2" mode="trackcom"/>
      <camera name="2a_side" pos="0 -3 1" xyaxes="1 0 0 0 1 2" mode="trackcom"/>
      <freejoint name="2a_root"/>
      <geom name="2a_torso" fromto="0 -.07 0 0 .07 0" size=".07"/>
      <geom name="2a_upper_waist" fromto="-.01 -.06 -.12 -.01 .06 -.12" size=".06"/>
      <body name="2a_head" pos="0 0 .19">
        <geom name="2a_head" type="sphere" size=".09"/>
        <camera name="2a_egocentric" pos=".09 0 0" xyaxes="0 -1 0 .1 0 1" fovy="80"/>
      </body>
      <body name="2a_lower_waist" pos="-.01 0 -.26">
        <geom name="2a_lower_waist" fromto="0 -.06 0 0 .06 0" size=".06"/>
        <joint name="2a_abdomen_z" pos="0 0 .065" axis="0 0 1" range="-45 45" class="big_stiff_joint"/>
        <joint name="2a_abdomen_y" pos="0 0 .065" axis="0 1 0" range="-75 30" class="big_joint"/>
        <body name="2a_pelvis" pos="0 0 -.165">
          <joint name="2a_abdomen_x" pos="0 0 .1" axis="1 0 0" range="-35 35" class="big_joint"/>
          <geom name="2a_butt" fromto="-.02 -.07 0 -.02 .07 0" size=".09"/>
          <body name="2a_right_thigh" pos="0 -.1 -.04">
            <joint name="2a_right_hip_x" axis="1 0 0" range="-25 5" class="big_joint"/>
            <joint name="2a_right_hip_z" axis="0 0 1" range="-60 35" class="big_joint"/>
            <joint name="2a_right_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="2a_right_thigh" fromto="0 0 0 0 .01 -.34" size=".06"/>
            <body name="2a_right_shin" pos="0 .01 -.403">
              <joint name="2a_right_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="2a_right_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="2a_right_foot" pos="0 0 -.39">
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                <geom name="2a_left_right_foot" fromto="-.07 0 0 .14  .02 0" size=".027"/>
              </body>
            </body>
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            <joint name="2a_left_hip_z" axis="0 0 -1" range="-60 35" class="big_joint"/>
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              <geom name="2a_left_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="2a_left_foot" pos="0 0 -.39">
                <joint name="2a_left_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="2a_left_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
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                <geom name="2a_right_left_foot" fromto="-.07 0 0 .14 -.02 0" size=".027"/>
              </body>
            </body>
          </body>
        </body>
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        <joint name="2a_right_shoulder1" axis="2 1 1"  range="-85 60"/>
        <joint name="2a_right_shoulder2" axis="0 -1 1" range="-85 60"/>
        <geom name="2a_right_upper_arm" fromto="0 0 0 .16 -.16 -.16" size=".04 .16"/>
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          <body name="2a_right_hand" pos=".18 .18 .18">
            <geom name="2a_right_hand" type="sphere" size=".04" zaxis="1 1 1"/>
          </body>
        </body>
      </body>
      <body name="2a_left_upper_arm" pos="0 .17 .06">
        <joint name="2a_left_shoulder1" axis="2 -1 1" range="-60 85"/>
        <joint name="2a_left_shoulder2" axis="0 1 1"  range="-60 85"/>
        <geom name="2a_left_upper_arm" fromto="0 0 0 .16 .16 -.16" size=".04 .16"/>
        <body name="2a_left_lower_arm" pos=".18 .18 -.18">
          <joint name="2a_left_elbow" axis="0 -1 -1" range="-90 50" stiffness="0"/>
          <geom name="2a_left_lower_arm" fromto=".01 -.01 .01 .17 -.17 .17" size=".031"/>
          <body name="2a_left_hand" pos=".18 -.18 .18">
            <geom name="2a_left_hand" type="sphere" size=".04" zaxis="1 -1 1"/>
          </body>
        </body>
      </body>
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      <camera name="3a_back" pos="-3 0 1" xyaxes="0 -1 0 1 0 2" mode="trackcom"/>
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      <freejoint name="3a_root"/>
      <geom name="3a_torso" fromto="0 -.07 0 0 .07 0" size=".07"/>
      <geom name="3a_upper_waist" fromto="-.01 -.06 -.12 -.01 .06 -.12" size=".06"/>
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        <geom name="3a_head" type="sphere" size=".09"/>
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        <geom name="3a_lower_waist" fromto="0 -.06 0 0 .06 0" size=".06"/>
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        <joint name="3a_abdomen_y" pos="0 0 .065" axis="0 1 0" range="-75 30" class="big_joint"/>
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            <joint name="3a_right_hip_x" axis="1 0 0" range="-25 5" class="big_joint"/>
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            <joint name="3a_right_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="3a_right_thigh" fromto="0 0 0 0 .01 -.34" size=".06"/>
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              <joint name="3a_right_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="3a_right_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="3a_right_foot" pos="0 0 -.39">
                <joint name="3a_right_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="3a_right_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="3a_right_right_foot" fromto="-.07 -.02 0 .14 -.04 0" size=".027"/>
                <geom name="3a_left_right_foot" fromto="-.07 0 0 .14  .02 0" size=".027"/>
              </body>
            </body>
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            <joint name="3a_left_hip_x" axis="-1 0 0" range="-25 5" class="big_joint"/>
            <joint name="3a_left_hip_z" axis="0 0 -1" range="-60 35" class="big_joint"/>
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            <geom name="3a_left_thigh" fromto="0 0 0 0 -.01 -.34" size=".06"/>
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              <joint name="3a_left_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="3a_left_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="3a_left_foot" pos="0 0 -.39">
                <joint name="3a_left_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="3a_left_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="3a_left_left_foot" fromto="-.07 .02 0 .14 .04 0" size=".027"/>
                <geom name="3a_right_left_foot" fromto="-.07 0 0 .14 -.02 0" size=".027"/>
              </body>
            </body>
          </body>
        </body>
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      <body name="3a_right_upper_arm" pos="0 -.17 .06">
        <joint name="3a_right_shoulder1" axis="2 1 1"  range="-85 60"/>
        <joint name="3a_right_shoulder2" axis="0 -1 1" range="-85 60"/>
        <geom name="3a_right_upper_arm" fromto="0 0 0 .16 -.16 -.16" size=".04 .16"/>
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          <geom name="3a_right_lower_arm" fromto=".01 .01 .01 .17 .17 .17" size=".031"/>
          <body name="3a_right_hand" pos=".18 .18 .18">
            <geom name="3a_right_hand" type="sphere" size=".04" zaxis="1 1 1"/>
          </body>
        </body>
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      <body name="3a_left_upper_arm" pos="0 .17 .06">
        <joint name="3a_left_shoulder1" axis="2 -1 1" range="-60 85"/>
        <joint name="3a_left_shoulder2" axis="0 1 1"  range="-60 85"/>
        <geom name="3a_left_upper_arm" fromto="0 0 0 .16 .16 -.16" size=".04 .16"/>
        <body name="3a_left_lower_arm" pos=".18 .18 -.18">
          <joint name="3a_left_elbow" axis="0 -1 -1" range="-90 50" stiffness="0"/>
          <geom name="3a_left_lower_arm" fromto=".01 -.01 .01 .17 -.17 .17" size=".031"/>
          <body name="3a_left_hand" pos=".18 -.18 .18">
            <geom name="3a_left_hand" type="sphere" size=".04" zaxis="1 -1 1"/>
          </body>
        </body>
      </body>
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      <camera name="4a_back" pos="-3 0 1" xyaxes="0 -1 0 1 0 2" mode="trackcom"/>
      <camera name="4a_side" pos="0 -3 1" xyaxes="1 0 0 0 1 2" mode="trackcom"/>
      <freejoint name="4a_root"/>
      <geom name="4a_torso" fromto="0 -.07 0 0 .07 0" size=".07"/>
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        <geom name="4a_head" type="sphere" size=".09"/>
        <camera name="4a_egocentric" pos=".09 0 0" xyaxes="0 -1 0 .1 0 1" fovy="80"/>
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        <joint name="4a_abdomen_y" pos="0 0 .065" axis="0 1 0" range="-75 30" class="big_joint"/>
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          <body name="4a_right_thigh" pos="0 -.1 -.04">
            <joint name="4a_right_hip_x" axis="1 0 0" range="-25 5" class="big_joint"/>
            <joint name="4a_right_hip_z" axis="0 0 1" range="-60 35" class="big_joint"/>
            <joint name="4a_right_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="4a_right_thigh" fromto="0 0 0 0 .01 -.34" size=".06"/>
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              <joint name="4a_right_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="4a_right_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="4a_right_foot" pos="0 0 -.39">
                <joint name="4a_right_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="4a_right_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="4a_right_right_foot" fromto="-.07 -.02 0 .14 -.04 0" size=".027"/>
                <geom name="4a_left_right_foot" fromto="-.07 0 0 .14  .02 0" size=".027"/>
              </body>
            </body>
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            <joint name="4a_left_hip_x" axis="-1 0 0" range="-25 5" class="big_joint"/>
            <joint name="4a_left_hip_z" axis="0 0 -1" range="-60 35" class="big_joint"/>
            <joint name="4a_left_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
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              <joint name="4a_left_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="4a_left_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="4a_left_foot" pos="0 0 -.39">
                <joint name="4a_left_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="4a_left_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="4a_left_left_foot" fromto="-.07 .02 0 .14 .04 0" size=".027"/>
                <geom name="4a_right_left_foot" fromto="-.07 0 0 .14 -.02 0" size=".027"/>
              </body>
            </body>
          </body>
        </body>
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        <joint name="4a_right_shoulder1" axis="2 1 1"  range="-85 60"/>
        <joint name="4a_right_shoulder2" axis="0 -1 1" range="-85 60"/>
        <geom name="4a_right_upper_arm" fromto="0 0 0 .16 -.16 -.16" size=".04 .16"/>
        <body name="4a_right_lower_arm" pos=".18 -.18 -.18">
          <joint name="4a_right_elbow" axis="0 -1 1" range="-90 50" stiffness="0"/>
          <geom name="4a_right_lower_arm" fromto=".01 .01 .01 .17 .17 .17" size=".031"/>
          <body name="4a_right_hand" pos=".18 .18 .18">
            <geom name="4a_right_hand" type="sphere" size=".04" zaxis="1 1 1"/>
          </body>
        </body>
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      <body name="4a_left_upper_arm" pos="0 .17 .06">
        <joint name="4a_left_shoulder1" axis="2 -1 1" range="-60 85"/>
        <joint name="4a_left_shoulder2" axis="0 1 1"  range="-60 85"/>
        <geom name="4a_left_upper_arm" fromto="0 0 0 .16 .16 -.16" size=".04 .16"/>
        <body name="4a_left_lower_arm" pos=".18 .18 -.18">
          <joint name="4a_left_elbow" axis="0 -1 -1" range="-90 50" stiffness="0"/>
          <geom name="4a_left_lower_arm" fromto=".01 -.01 .01 .17 -.17 .17" size=".031"/>
          <body name="4a_left_hand" pos=".18 -.18 .18">
            <geom name="4a_left_hand" type="sphere" size=".04" zaxis="1 -1 1"/>
          </body>
        </body>
      </body>
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      <camera name="5a_back" pos="-3 0 1" xyaxes="0 -1 0 1 0 2" mode="trackcom"/>
      <camera name="5a_side" pos="0 -3 1" xyaxes="1 0 0 0 1 2" mode="trackcom"/>
      <freejoint name="5a_root"/>
      <geom name="5a_torso" fromto="0 -.07 0 0 .07 0" size=".07"/>
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        <geom name="5a_head" type="sphere" size=".09"/>
        <camera name="5a_egocentric" pos=".09 0 0" xyaxes="0 -1 0 .1 0 1" fovy="80"/>
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      <body name="5a_lower_waist" pos="-.01 0 -.26">
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        <joint name="5a_abdomen_y" pos="0 0 .065" axis="0 1 0" range="-75 30" class="big_joint"/>
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            <joint name="5a_right_hip_x" axis="1 0 0" range="-25 5" class="big_joint"/>
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            <joint name="5a_right_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="5a_right_thigh" fromto="0 0 0 0 .01 -.34" size=".06"/>
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              <geom name="5a_right_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="5a_right_foot" pos="0 0 -.39">
                <joint name="5a_right_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="5a_right_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="5a_right_right_foot" fromto="-.07 -.02 0 .14 -.04 0" size=".027"/>
                <geom name="5a_left_right_foot" fromto="-.07 0 0 .14  .02 0" size=".027"/>
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            <joint name="5a_left_hip_z" axis="0 0 -1" range="-60 35" class="big_joint"/>
            <joint name="5a_left_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
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              <joint name="5a_left_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="5a_left_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="5a_left_foot" pos="0 0 -.39">
                <joint name="5a_left_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="5a_left_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="5a_left_left_foot" fromto="-.07 .02 0 .14 .04 0" size=".027"/>
                <geom name="5a_right_left_foot" fromto="-.07 0 0 .14 -.02 0" size=".027"/>
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            </body>
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      <body name="5a_right_upper_arm" pos="0 -.17 .06">
        <joint name="5a_right_shoulder1" axis="2 1 1"  range="-85 60"/>
        <joint name="5a_right_shoulder2" axis="0 -1 1" range="-85 60"/>
        <geom name="5a_right_upper_arm" fromto="0 0 0 .16 -.16 -.16" size=".04 .16"/>
        <body name="5a_right_lower_arm" pos=".18 -.18 -.18">
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          <geom name="5a_right_lower_arm" fromto=".01 .01 .01 .17 .17 .17" size=".031"/>
          <body name="5a_right_hand" pos=".18 .18 .18">
            <geom name="5a_right_hand" type="sphere" size=".04" zaxis="1 1 1"/>
          </body>
        </body>
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      <body name="5a_left_upper_arm" pos="0 .17 .06">
        <joint name="5a_left_shoulder1" axis="2 -1 1" range="-60 85"/>
        <joint name="5a_left_shoulder2" axis="0 1 1"  range="-60 85"/>
        <geom name="5a_left_upper_arm" fromto="0 0 0 .16 .16 -.16" size=".04 .16"/>
        <body name="5a_left_lower_arm" pos=".18 .18 -.18">
          <joint name="5a_left_elbow" axis="0 -1 -1" range="-90 50" stiffness="0"/>
          <geom name="5a_left_lower_arm" fromto=".01 -.01 .01 .17 -.17 .17" size=".031"/>
          <body name="5a_left_hand" pos=".18 -.18 .18">
            <geom name="5a_left_hand" type="sphere" size=".04" zaxis="1 -1 1"/>
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        </body>
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      <camera name="6a_side" pos="0 -3 1" xyaxes="1 0 0 0 1 2" mode="trackcom"/>
      <freejoint name="6a_root"/>
      <geom name="6a_torso" fromto="0 -.07 0 0 .07 0" size=".07"/>
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        <geom name="6a_head" type="sphere" size=".09"/>
        <camera name="6a_egocentric" pos=".09 0 0" xyaxes="0 -1 0 .1 0 1" fovy="80"/>
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        <joint name="6a_abdomen_y" pos="0 0 .065" axis="0 1 0" range="-75 30" class="big_joint"/>
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              <geom name="6a_right_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="6a_right_foot" pos="0 0 -.39">
                <joint name="6a_right_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="6a_right_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="6a_right_right_foot" fromto="-.07 -.02 0 .14 -.04 0" size=".027"/>
                <geom name="6a_left_right_foot" fromto="-.07 0 0 .14  .02 0" size=".027"/>
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            <joint name="6a_left_hip_z" axis="0 0 -1" range="-60 35" class="big_joint"/>
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            <geom name="6a_left_thigh" fromto="0 0 0 0 -.01 -.34" size=".06"/>
            <body name="6a_left_shin" pos="0 -.01 -.403">
              <joint name="6a_left_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="6a_left_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="6a_left_foot" pos="0 0 -.39">
                <joint name="6a_left_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="6a_left_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="6a_left_left_foot" fromto="-.07 .02 0 .14 .04 0" size=".027"/>
                <geom name="6a_right_left_foot" fromto="-.07 0 0 .14 -.02 0" size=".027"/>
              </body>
            </body>
          </body>
        </body>
      </body>
      <body name="6a_right_upper_arm" pos="0 -.17 .06">
        <joint name="6a_right_shoulder1" axis="2 1 1"  range="-85 60"/>
        <joint name="6a_right_shoulder2" axis="0 -1 1" range="-85 60"/>
        <geom name="6a_right_upper_arm" fromto="0 0 0 .16 -.16 -.16" size=".04 .16"/>
        <body name="6a_right_lower_arm" pos=".18 -.18 -.18">
          <joint name="6a_right_elbow" axis="0 -1 1" range="-90 50" stiffness="0"/>
          <geom name="6a_right_lower_arm" fromto=".01 .01 .01 .17 .17 .17" size=".031"/>
          <body name="6a_right_hand" pos=".18 .18 .18">
            <geom name="6a_right_hand" type="sphere" size=".04" zaxis="1 1 1"/>
          </body>
        </body>
      </body>
      <body name="6a_left_upper_arm" pos="0 .17 .06">
        <joint name="6a_left_shoulder1" axis="2 -1 1" range="-60 85"/>
        <joint name="6a_left_shoulder2" axis="0 1 1"  range="-60 85"/>
        <geom name="6a_left_upper_arm" fromto="0 0 0 .16 .16 -.16" size=".04 .16"/>
        <body name="6a_left_lower_arm" pos=".18 .18 -.18">
          <joint name="6a_left_elbow" axis="0 -1 -1" range="-90 50" stiffness="0"/>
          <geom name="6a_left_lower_arm" fromto=".01 -.01 .01 .17 -.17 .17" size=".031"/>
          <body name="6a_left_hand" pos=".18 -.18 .18">
            <geom name="6a_left_hand" type="sphere" size=".04" zaxis="1 -1 1"/>
          </body>
        </body>
      </body>
    </body>
  </worldbody>
  <actuator>
    <motor gear="40"  joint="1a_abdomen_y"/>
    <motor gear="40"  joint="1a_abdomen_z"/>
    <motor gear="40"  joint="1a_abdomen_x"/>
    <motor gear="40"  joint="1a_right_hip_x"/>
    <motor gear="40"  joint="1a_right_hip_z"/>
    <motor gear="120" joint="1a_right_hip_y"/>
    <motor gear="80"  joint="1a_right_knee"/>
    <motor gear="20"  joint="1a_right_ankle_x"/>
    <motor gear="20"  joint="1a_right_ankle_y"/>
    <motor gear="40"  joint="1a_left_hip_x"/>
    <motor gear="40"  joint="1a_left_hip_z"/>
    <motor gear="120" joint="1a_left_hip_y"/>
    <motor gear="80"  joint="1a_left_knee"/>
    <motor gear="20"  joint="1a_left_ankle_x"/>
    <motor gear="20"  joint="1a_left_ankle_y"/>
    <motor gear="20"  joint="1a_right_shoulder1"/>
    <motor gear="20"  joint="1a_right_shoulder2"/>
    <motor gear="40"  joint="1a_right_elbow"/>
    <motor gear="20"  joint="1a_left_shoulder1"/>
    <motor gear="20"  joint="1a_left_shoulder2"/>
    <motor gear="40"  joint="1a_left_elbow"/>
  </actuator>
  <actuator>
    <motor gear="40"  joint="2a_abdomen_y"/>
    <motor gear="40"  joint="2a_abdomen_z"/>
    <motor gear="40"  joint="2a_abdomen_x"/>
    <motor gear="40"  joint="2a_right_hip_x"/>
    <motor gear="40"  joint="2a_right_hip_z"/>
    <motor gear="120" joint="2a_right_hip_y"/>
    <motor gear="80"  joint="2a_right_knee"/>
    <motor gear="20"  joint="2a_right_ankle_x"/>
    <motor gear="20"  joint="2a_right_ankle_y"/>
    <motor gear="40"  joint="2a_left_hip_x"/>
    <motor gear="40"  joint="2a_left_hip_z"/>
    <motor gear="120" joint="2a_left_hip_y"/>
    <motor gear="80"  joint="2a_left_knee"/>
    <motor gear="20"  joint="2a_left_ankle_x"/>
    <motor gear="20"  joint="2a_left_ankle_y"/>
    <motor gear="20"  joint="2a_right_shoulder1"/>
    <motor gear="20"  joint="2a_right_shoulder2"/>
    <motor gear="40"  joint="2a_right_elbow"/>
    <motor gear="20"  joint="2a_left_shoulder1"/>
    <motor gear="20"  joint="2a_left_shoulder2"/>
    <motor gear="40"  joint="2a_left_elbow"/>
  </actuator>
  <actuator>
    <motor gear="40"  joint="3a_abdomen_y"/>
    <motor gear="40"  joint="3a_abdomen_z"/>
    <motor gear="40"  joint="3a_abdomen_x"/>
    <motor gear="40"  joint="3a_right_hip_x"/>
    <motor gear="40"  joint="3a_right_hip_z"/>
    <motor gear="120" joint="3a_right_hip_y"/>
    <motor gear="80"  joint="3a_right_knee"/>
    <motor gear="20"  joint="3a_right_ankle_x"/>
    <motor gear="20"  joint="3a_right_ankle_y"/>
    <motor gear="40"  joint="3a_left_hip_x"/>
    <motor gear="40"  joint="3a_left_hip_z"/>
    <motor gear="120" joint="3a_left_hip_y"/>
    <motor gear="80"  joint="3a_left_knee"/>
    <motor gear="20"  joint="3a_left_ankle_x"/>
    <motor gear="20"  joint="3a_left_ankle_y"/>
    <motor gear="20"  joint="3a_right_shoulder1"/>
    <motor gear="20"  joint="3a_right_shoulder2"/>
    <motor gear="40"  joint="3a_right_elbow"/>
    <motor gear="20"  joint="3a_left_shoulder1"/>
    <motor gear="20"  joint="3a_left_shoulder2"/>
    <motor gear="40"  joint="3a_left_elbow"/>
  </actuator>
  <actuator>
    <motor gear="40"  joint="4a_abdomen_y"/>
    <motor gear="40"  joint="4a_abdomen_z"/>
    <motor gear="40"  joint="4a_abdomen_x"/>
    <motor gear="40"  joint="4a_right_hip_x"/>
    <motor gear="40"  joint="4a_right_hip_z"/>
    <motor gear="120" joint="4a_right_hip_y"/>
    <motor gear="80"  joint="4a_right_knee"/>
    <motor gear="20"  joint="4a_right_ankle_x"/>
    <motor gear="20"  joint="4a_right_ankle_y"/>
    <motor gear="40"  joint="4a_left_hip_x"/>
    <motor gear="40"  joint="4a_left_hip_z"/>
    <motor gear="120" joint="4a_left_hip_y"/>
    <motor gear="80"  joint="4a_left_knee"/>
    <motor gear="20"  joint="4a_left_ankle_x"/>
    <motor gear="20"  joint="4a_left_ankle_y"/>
    <motor gear="20"  joint="4a_right_shoulder1"/>
    <motor gear="20"  joint="4a_right_shoulder2"/>
    <motor gear="40"  joint="4a_right_elbow"/>
    <motor gear="20"  joint="4a_left_shoulder1"/>
    <motor gear="20"  joint="4a_left_shoulder2"/>
    <motor gear="40"  joint="4a_left_elbow"/>
  </actuator>
  <actuator>
    <motor gear="40"  joint="5a_abdomen_y"/>
    <motor gear="40"  joint="5a_abdomen_z"/>
    <motor gear="40"  joint="5a_abdomen_x"/>
    <motor gear="40"  joint="5a_right_hip_x"/>
    <motor gear="40"  joint="5a_right_hip_z"/>
    <motor gear="120" joint="5a_right_hip_y"/>
    <motor gear="80"  joint="5a_right_knee"/>
    <motor gear="20"  joint="5a_right_ankle_x"/>
    <motor gear="20"  joint="5a_right_ankle_y"/>
    <motor gear="40"  joint="5a_left_hip_x"/>
    <motor gear="40"  joint="5a_left_hip_z"/>
    <motor gear="120" joint="5a_left_hip_y"/>
    <motor gear="80"  joint="5a_left_knee"/>
    <motor gear="20"  joint="5a_left_ankle_x"/>
    <motor gear="20"  joint="5a_left_ankle_y"/>
    <motor gear="20"  joint="5a_right_shoulder1"/>
    <motor gear="20"  joint="5a_right_shoulder2"/>
    <motor gear="40"  joint="5a_right_elbow"/>
    <motor gear="20"  joint="5a_left_shoulder1"/>
    <motor gear="20"  joint="5a_left_shoulder2"/>
    <motor gear="40"  joint="5a_left_elbow"/>
  </actuator>
  <actuator>
    <motor gear="40"  joint="6a_abdomen_y"/>
    <motor gear="40"  joint="6a_abdomen_z"/>
    <motor gear="40"  joint="6a_abdomen_x"/>
    <motor gear="40"  joint="6a_right_hip_x"/>
    <motor gear="40"  joint="6a_right_hip_z"/>
    <motor gear="120" joint="6a_right_hip_y"/>
    <motor gear="80"  joint="6a_right_knee"/>
    <motor gear="20"  joint="6a_right_ankle_x"/>
    <motor gear="20"  joint="6a_right_ankle_y"/>
    <motor gear="40"  joint="6a_left_hip_x"/>
    <motor gear="40"  joint="6a_left_hip_z"/>
    <motor gear="120" joint="6a_left_hip_y"/>
    <motor gear="80"  joint="6a_left_knee"/>
    <motor gear="20"  joint="6a_left_ankle_x"/>
    <motor gear="20"  joint="6a_left_ankle_y"/>
    <motor gear="20"  joint="6a_right_shoulder1"/>
    <motor gear="20"  joint="6a_right_shoulder2"/>
    <motor gear="40"  joint="6a_right_elbow"/>
    <motor gear="20"  joint="6a_left_shoulder1"/>
    <motor gear="20"  joint="6a_left_shoulder2"/>
    <motor gear="40"  joint="6a_left_elbow"/>
  </actuator>
 </mujoco>
@@ -0,0 +1,775 @@
 <mujoco model="07 Humanoids">
  <option timestep="0.005" solver="Newton" iterations="1" ls_iterations="4">
    <flag eulerdamp="disable"/>
  </option>
  <custom>
    <numeric data="28" name="max_contact_points"/>
    <numeric data="28" name="max_geom_pairs"/>
  </custom>
  <size memory="100M"/>
  <asset>
    <texture type="skybox" builtin="gradient" rgb1=".3 .5 .7" rgb2="0 0 0" width="512" height="512"/>
    <texture name="body" type="cube" builtin="flat" mark="cross" width="128" height="128"
             rgb1="0.8 0.6 0.4" rgb2="0.8 0.6 0.4" markrgb="1 1 1" random="0.01"/>
    <material name="body" texture="body" texuniform="true" rgba="0.8 0.6 .4 1"/>
    <texture name="grid" type="2d" builtin="checker" width="512" height="512" rgb1=".1 .2 .3" rgb2=".2 .3 .4"/>
    <material name="grid" texture="grid" texrepeat="1 1" texuniform="true" reflectance=".2"/>
  </asset>
  <default>
    <motor ctrlrange="-1 1" ctrllimited="true"/>
    <joint type="hinge" damping=".2" stiffness="1" armature=".01" limited="true" solimplimit="0 .99 .01"/>
    <default class="big_joint">
      <joint damping="5" stiffness="10"/>
      <default class="big_stiff_joint">
        <joint stiffness="20"/>
      </default>
    </default>
    <default class="body1">
      <geom type="capsule" condim="3" friction=".7" solimp=".9 .99 .003" solref=".015 1" material="body" contype="2" conaffinity="253"/>
    </default>
    <default class="body2">
      <geom type="capsule" condim="3" friction=".7" solimp=".9 .99 .003" solref=".015 1" material="body" contype="4" conaffinity="251"/>
    </default>
    <default class="body3">
      <geom type="capsule" condim="3" friction=".7" solimp=".9 .99 .003" solref=".015 1" material="body" contype="8" conaffinity="247"/>
    </default>
    <default class="body4">
      <geom type="capsule" condim="3" friction=".7" solimp=".9 .99 .003" solref=".015 1" material="body" contype="16" conaffinity="239"/>
    </default>
    <default class="body5">
      <geom type="capsule" condim="3" friction=".7" solimp=".9 .99 .003" solref=".015 1" material="body" contype="32" conaffinity="223"/>
    </default>
    <default class="body6">
      <geom type="capsule" condim="3" friction=".7" solimp=".9 .99 .003" solref=".015 1" material="body" contype="64" conaffinity="191"/>
    </default>
    <default class="body7">
      <geom type="capsule" condim="3" friction=".7" solimp=".9 .99 .003" solref=".015 1" material="body" contype="128" conaffinity="127"/>
    </default>
  </default>
  <visual>
    <map force="0.1" zfar="30"/>
    <rgba haze="0.15 0.25 0.35 1"/>
    <quality shadowsize="4096"/>
    <global offwidth="800" offheight="800"/>
  </visual>
  <worldbody>
    <geom size="10 10 .05" type="plane" material="grid" condim="3"/>
    <light dir=".2 1 -.4" diffuse=".8 .8 .8" specular="0.3 0.3 0.3" pos="-2 -10 4" cutoff="35"/>
    <light dir="-.2 1 -.4" diffuse=".8 .8 .8" specular="0.3 0.3 0.3" pos="2 -10 4" cutoff="35"/>
    <body name="1a_torso" pos="-1 0 1.5" childclass="body1">
      <camera name="1a_back" pos="-3 0 1" xyaxes="0 -1 0 1 0 2" mode="trackcom"/>
      <camera name="1a_side" pos="0 -3 1" xyaxes="1 0 0 0 1 2" mode="trackcom"/>
      <freejoint name="1a_root"/>
      <geom name="1a_torso" fromto="0 -.07 0 0 .07 0" size=".07"/>
      <geom name="1a_upper_waist" fromto="-.01 -.06 -.12 -.01 .06 -.12" size=".06"/>
      <body name="1a_head" pos="0 0 .19">
        <geom name="1a_head" type="sphere" size=".09"/>
        <camera name="1a_egocentric" pos=".09 0 0" xyaxes="0 -1 0 .1 0 1" fovy="80"/>
      </body>
      <body name="1a_lower_waist" pos="-.01 0 -.26">
        <geom name="1a_lower_waist" fromto="0 -.06 0 0 .06 0" size=".06"/>
        <joint name="1a_abdomen_z" pos="0 0 .065" axis="0 0 1" range="-45 45" class="big_stiff_joint"/>
        <joint name="1a_abdomen_y" pos="0 0 .065" axis="0 1 0" range="-75 30" class="big_joint"/>
        <body name="1a_pelvis" pos="0 0 -.165">
          <joint name="1a_abdomen_x" pos="0 0 .1" axis="1 0 0" range="-35 35" class="big_joint"/>
          <geom name="1a_butt" fromto="-.02 -.07 0 -.02 .07 0" size=".09"/>
          <body name="1a_right_thigh" pos="0 -.1 -.04">
            <joint name="1a_right_hip_x" axis="1 0 0" range="-25 5" class="big_joint"/>
            <joint name="1a_right_hip_z" axis="0 0 1" range="-60 35" class="big_joint"/>
            <joint name="1a_right_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="1a_right_thigh" fromto="0 0 0 0 .01 -.34" size=".06"/>
            <body name="1a_right_shin" pos="0 .01 -.403">
              <joint name="1a_right_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="1a_right_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="1a_right_foot" pos="0 0 -.39">
                <joint name="1a_right_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="1a_right_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="1a_right_right_foot" fromto="-.07 -.02 0 .14 -.04 0" size=".027"/>
                <geom name="1a_left_right_foot" fromto="-.07 0 0 .14  .02 0" size=".027"/>
              </body>
            </body>
          </body>
          <body name="1a_left_thigh" pos="0 .1 -.04">
            <joint name="1a_left_hip_x" axis="-1 0 0" range="-25 5" class="big_joint"/>
            <joint name="1a_left_hip_z" axis="0 0 -1" range="-60 35" class="big_joint"/>
            <joint name="1a_left_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="1a_left_thigh" fromto="0 0 0 0 -.01 -.34" size=".06"/>
            <body name="1a_left_shin" pos="0 -.01 -.403">
              <joint name="1a_left_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="1a_left_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="1a_left_foot" pos="0 0 -.39">
                <joint name="1a_left_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="1a_left_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="1a_left_left_foot" fromto="-.07 .02 0 .14 .04 0" size=".027"/>
                <geom name="1a_right_left_foot" fromto="-.07 0 0 .14 -.02 0" size=".027"/>
              </body>
            </body>
          </body>
        </body>
      </body>
      <body name="1a_right_upper_arm" pos="0 -.17 .06">
        <joint name="1a_right_shoulder1" axis="2 1 1"  range="-85 60"/>
        <joint name="1a_right_shoulder2" axis="0 -1 1" range="-85 60"/>
        <geom name="1a_right_upper_arm" fromto="0 0 0 .16 -.16 -.16" size=".04 .16"/>
        <body name="1a_right_lower_arm" pos=".18 -.18 -.18">
          <joint name="1a_right_elbow" axis="0 -1 1" range="-90 50" stiffness="0"/>
          <geom name="1a_right_lower_arm" fromto=".01 .01 .01 .17 .17 .17" size=".031"/>
          <body name="1a_right_hand" pos=".18 .18 .18">
            <geom name="1a_right_hand" type="sphere" size=".04" zaxis="1 1 1"/>
          </body>
        </body>
      </body>
      <body name="1a_left_upper_arm" pos="0 .17 .06">
        <joint name="1a_left_shoulder1" axis="2 -1 1" range="-60 85"/>
        <joint name="1a_left_shoulder2" axis="0 1 1"  range="-60 85"/>
        <geom name="1a_left_upper_arm" fromto="0 0 0 .16 .16 -.16" size=".04 .16"/>
        <body name="1a_left_lower_arm" pos=".18 .18 -.18">
          <joint name="1a_left_elbow" axis="0 -1 -1" range="-90 50" stiffness="0"/>
          <geom name="1a_left_lower_arm" fromto=".01 -.01 .01 .17 -.17 .17" size=".031"/>
          <body name="1a_left_hand" pos=".18 -.18 .18">
            <geom name="1a_left_hand" type="sphere" size=".04" zaxis="1 -1 1"/>
          </body>
        </body>
      </body>
    </body>
    <body name="2a_torso" pos="-1 1 1.5" childclass="body2">
      <camera name="2a_back" pos="-3 0 1" xyaxes="0 -1 0 1 0 2" mode="trackcom"/>
      <camera name="2a_side" pos="0 -3 1" xyaxes="1 0 0 0 1 2" mode="trackcom"/>
      <freejoint name="2a_root"/>
      <geom name="2a_torso" fromto="0 -.07 0 0 .07 0" size=".07"/>
      <geom name="2a_upper_waist" fromto="-.01 -.06 -.12 -.01 .06 -.12" size=".06"/>
      <body name="2a_head" pos="0 0 .19">
        <geom name="2a_head" type="sphere" size=".09"/>
        <camera name="2a_egocentric" pos=".09 0 0" xyaxes="0 -1 0 .1 0 1" fovy="80"/>
      </body>
      <body name="2a_lower_waist" pos="-.01 0 -.26">
        <geom name="2a_lower_waist" fromto="0 -.06 0 0 .06 0" size=".06"/>
        <joint name="2a_abdomen_z" pos="0 0 .065" axis="0 0 1" range="-45 45" class="big_stiff_joint"/>
        <joint name="2a_abdomen_y" pos="0 0 .065" axis="0 1 0" range="-75 30" class="big_joint"/>
        <body name="2a_pelvis" pos="0 0 -.165">
          <joint name="2a_abdomen_x" pos="0 0 .1" axis="1 0 0" range="-35 35" class="big_joint"/>
          <geom name="2a_butt" fromto="-.02 -.07 0 -.02 .07 0" size=".09"/>
          <body name="2a_right_thigh" pos="0 -.1 -.04">
            <joint name="2a_right_hip_x" axis="1 0 0" range="-25 5" class="big_joint"/>
            <joint name="2a_right_hip_z" axis="0 0 1" range="-60 35" class="big_joint"/>
            <joint name="2a_right_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="2a_right_thigh" fromto="0 0 0 0 .01 -.34" size=".06"/>
            <body name="2a_right_shin" pos="0 .01 -.403">
              <joint name="2a_right_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="2a_right_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="2a_right_foot" pos="0 0 -.39">
                <joint name="2a_right_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="2a_right_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="2a_right_right_foot" fromto="-.07 -.02 0 .14 -.04 0" size=".027"/>
                <geom name="2a_left_right_foot" fromto="-.07 0 0 .14  .02 0" size=".027"/>
              </body>
            </body>
          </body>
          <body name="2a_left_thigh" pos="0 .1 -.04">
            <joint name="2a_left_hip_x" axis="-1 0 0" range="-25 5" class="big_joint"/>
            <joint name="2a_left_hip_z" axis="0 0 -1" range="-60 35" class="big_joint"/>
            <joint name="2a_left_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="2a_left_thigh" fromto="0 0 0 0 -.01 -.34" size=".06"/>
            <body name="2a_left_shin" pos="0 -.01 -.403">
              <joint name="2a_left_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="2a_left_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="2a_left_foot" pos="0 0 -.39">
                <joint name="2a_left_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="2a_left_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="2a_left_left_foot" fromto="-.07 .02 0 .14 .04 0" size=".027"/>
                <geom name="2a_right_left_foot" fromto="-.07 0 0 .14 -.02 0" size=".027"/>
              </body>
            </body>
          </body>
        </body>
      </body>
      <body name="2a_right_upper_arm" pos="0 -.17 .06">
        <joint name="2a_right_shoulder1" axis="2 1 1"  range="-85 60"/>
        <joint name="2a_right_shoulder2" axis="0 -1 1" range="-85 60"/>
        <geom name="2a_right_upper_arm" fromto="0 0 0 .16 -.16 -.16" size=".04 .16"/>
        <body name="2a_right_lower_arm" pos=".18 -.18 -.18">
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          <body name="2a_right_hand" pos=".18 .18 .18">
            <geom name="2a_right_hand" type="sphere" size=".04" zaxis="1 1 1"/>
          </body>
        </body>
      </body>
      <body name="2a_left_upper_arm" pos="0 .17 .06">
        <joint name="2a_left_shoulder1" axis="2 -1 1" range="-60 85"/>
        <joint name="2a_left_shoulder2" axis="0 1 1"  range="-60 85"/>
        <geom name="2a_left_upper_arm" fromto="0 0 0 .16 .16 -.16" size=".04 .16"/>
        <body name="2a_left_lower_arm" pos=".18 .18 -.18">
          <joint name="2a_left_elbow" axis="0 -1 -1" range="-90 50" stiffness="0"/>
          <geom name="2a_left_lower_arm" fromto=".01 -.01 .01 .17 -.17 .17" size=".031"/>
          <body name="2a_left_hand" pos=".18 -.18 .18">
            <geom name="2a_left_hand" type="sphere" size=".04" zaxis="1 -1 1"/>
          </body>
        </body>
      </body>
    </body>
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      <camera name="3a_back" pos="-3 0 1" xyaxes="0 -1 0 1 0 2" mode="trackcom"/>
      <camera name="3a_side" pos="0 -3 1" xyaxes="1 0 0 0 1 2" mode="trackcom"/>
      <freejoint name="3a_root"/>
      <geom name="3a_torso" fromto="0 -.07 0 0 .07 0" size=".07"/>
      <geom name="3a_upper_waist" fromto="-.01 -.06 -.12 -.01 .06 -.12" size=".06"/>
      <body name="3a_head" pos="0 0 .19">
        <geom name="3a_head" type="sphere" size=".09"/>
        <camera name="3a_egocentric" pos=".09 0 0" xyaxes="0 -1 0 .1 0 1" fovy="80"/>
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        <geom name="3a_lower_waist" fromto="0 -.06 0 0 .06 0" size=".06"/>
        <joint name="3a_abdomen_z" pos="0 0 .065" axis="0 0 1" range="-45 45" class="big_stiff_joint"/>
        <joint name="3a_abdomen_y" pos="0 0 .065" axis="0 1 0" range="-75 30" class="big_joint"/>
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          <body name="3a_right_thigh" pos="0 -.1 -.04">
            <joint name="3a_right_hip_x" axis="1 0 0" range="-25 5" class="big_joint"/>
            <joint name="3a_right_hip_z" axis="0 0 1" range="-60 35" class="big_joint"/>
            <joint name="3a_right_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="3a_right_thigh" fromto="0 0 0 0 .01 -.34" size=".06"/>
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              <joint name="3a_right_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="3a_right_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="3a_right_foot" pos="0 0 -.39">
                <joint name="3a_right_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="3a_right_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="3a_right_right_foot" fromto="-.07 -.02 0 .14 -.04 0" size=".027"/>
                <geom name="3a_left_right_foot" fromto="-.07 0 0 .14  .02 0" size=".027"/>
              </body>
            </body>
          </body>
          <body name="3a_left_thigh" pos="0 .1 -.04">
            <joint name="3a_left_hip_x" axis="-1 0 0" range="-25 5" class="big_joint"/>
            <joint name="3a_left_hip_z" axis="0 0 -1" range="-60 35" class="big_joint"/>
            <joint name="3a_left_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="3a_left_thigh" fromto="0 0 0 0 -.01 -.34" size=".06"/>
            <body name="3a_left_shin" pos="0 -.01 -.403">
              <joint name="3a_left_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="3a_left_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="3a_left_foot" pos="0 0 -.39">
                <joint name="3a_left_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="3a_left_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="3a_left_left_foot" fromto="-.07 .02 0 .14 .04 0" size=".027"/>
                <geom name="3a_right_left_foot" fromto="-.07 0 0 .14 -.02 0" size=".027"/>
              </body>
            </body>
          </body>
        </body>
      </body>
      <body name="3a_right_upper_arm" pos="0 -.17 .06">
        <joint name="3a_right_shoulder1" axis="2 1 1"  range="-85 60"/>
        <joint name="3a_right_shoulder2" axis="0 -1 1" range="-85 60"/>
        <geom name="3a_right_upper_arm" fromto="0 0 0 .16 -.16 -.16" size=".04 .16"/>
        <body name="3a_right_lower_arm" pos=".18 -.18 -.18">
          <joint name="3a_right_elbow" axis="0 -1 1" range="-90 50" stiffness="0"/>
          <geom name="3a_right_lower_arm" fromto=".01 .01 .01 .17 .17 .17" size=".031"/>
          <body name="3a_right_hand" pos=".18 .18 .18">
            <geom name="3a_right_hand" type="sphere" size=".04" zaxis="1 1 1"/>
          </body>
        </body>
      </body>
      <body name="3a_left_upper_arm" pos="0 .17 .06">
        <joint name="3a_left_shoulder1" axis="2 -1 1" range="-60 85"/>
        <joint name="3a_left_shoulder2" axis="0 1 1"  range="-60 85"/>
        <geom name="3a_left_upper_arm" fromto="0 0 0 .16 .16 -.16" size=".04 .16"/>
        <body name="3a_left_lower_arm" pos=".18 .18 -.18">
          <joint name="3a_left_elbow" axis="0 -1 -1" range="-90 50" stiffness="0"/>
          <geom name="3a_left_lower_arm" fromto=".01 -.01 .01 .17 -.17 .17" size=".031"/>
          <body name="3a_left_hand" pos=".18 -.18 .18">
            <geom name="3a_left_hand" type="sphere" size=".04" zaxis="1 -1 1"/>
          </body>
        </body>
      </body>
    </body>
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      <camera name="4a_back" pos="-3 0 1" xyaxes="0 -1 0 1 0 2" mode="trackcom"/>
      <camera name="4a_side" pos="0 -3 1" xyaxes="1 0 0 0 1 2" mode="trackcom"/>
      <freejoint name="4a_root"/>
      <geom name="4a_torso" fromto="0 -.07 0 0 .07 0" size=".07"/>
      <geom name="4a_upper_waist" fromto="-.01 -.06 -.12 -.01 .06 -.12" size=".06"/>
      <body name="4a_head" pos="0 0 .19">
        <geom name="4a_head" type="sphere" size=".09"/>
        <camera name="4a_egocentric" pos=".09 0 0" xyaxes="0 -1 0 .1 0 1" fovy="80"/>
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      <body name="4a_lower_waist" pos="-.01 0 -.26">
        <geom name="4a_lower_waist" fromto="0 -.06 0 0 .06 0" size=".06"/>
        <joint name="4a_abdomen_z" pos="0 0 .065" axis="0 0 1" range="-45 45" class="big_stiff_joint"/>
        <joint name="4a_abdomen_y" pos="0 0 .065" axis="0 1 0" range="-75 30" class="big_joint"/>
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          <joint name="4a_abdomen_x" pos="0 0 .1" axis="1 0 0" range="-35 35" class="big_joint"/>
          <geom name="4a_butt" fromto="-.02 -.07 0 -.02 .07 0" size=".09"/>
          <body name="4a_right_thigh" pos="0 -.1 -.04">
            <joint name="4a_right_hip_x" axis="1 0 0" range="-25 5" class="big_joint"/>
            <joint name="4a_right_hip_z" axis="0 0 1" range="-60 35" class="big_joint"/>
            <joint name="4a_right_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="4a_right_thigh" fromto="0 0 0 0 .01 -.34" size=".06"/>
            <body name="4a_right_shin" pos="0 .01 -.403">
              <joint name="4a_right_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="4a_right_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="4a_right_foot" pos="0 0 -.39">
                <joint name="4a_right_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="4a_right_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="4a_right_right_foot" fromto="-.07 -.02 0 .14 -.04 0" size=".027"/>
                <geom name="4a_left_right_foot" fromto="-.07 0 0 .14  .02 0" size=".027"/>
              </body>
            </body>
          </body>
          <body name="4a_left_thigh" pos="0 .1 -.04">
            <joint name="4a_left_hip_x" axis="-1 0 0" range="-25 5" class="big_joint"/>
            <joint name="4a_left_hip_z" axis="0 0 -1" range="-60 35" class="big_joint"/>
            <joint name="4a_left_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="4a_left_thigh" fromto="0 0 0 0 -.01 -.34" size=".06"/>
            <body name="4a_left_shin" pos="0 -.01 -.403">
              <joint name="4a_left_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="4a_left_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="4a_left_foot" pos="0 0 -.39">
                <joint name="4a_left_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="4a_left_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="4a_left_left_foot" fromto="-.07 .02 0 .14 .04 0" size=".027"/>
                <geom name="4a_right_left_foot" fromto="-.07 0 0 .14 -.02 0" size=".027"/>
              </body>
            </body>
          </body>
        </body>
      </body>
      <body name="4a_right_upper_arm" pos="0 -.17 .06">
        <joint name="4a_right_shoulder1" axis="2 1 1"  range="-85 60"/>
        <joint name="4a_right_shoulder2" axis="0 -1 1" range="-85 60"/>
        <geom name="4a_right_upper_arm" fromto="0 0 0 .16 -.16 -.16" size=".04 .16"/>
        <body name="4a_right_lower_arm" pos=".18 -.18 -.18">
          <joint name="4a_right_elbow" axis="0 -1 1" range="-90 50" stiffness="0"/>
          <geom name="4a_right_lower_arm" fromto=".01 .01 .01 .17 .17 .17" size=".031"/>
          <body name="4a_right_hand" pos=".18 .18 .18">
            <geom name="4a_right_hand" type="sphere" size=".04" zaxis="1 1 1"/>
          </body>
        </body>
      </body>
      <body name="4a_left_upper_arm" pos="0 .17 .06">
        <joint name="4a_left_shoulder1" axis="2 -1 1" range="-60 85"/>
        <joint name="4a_left_shoulder2" axis="0 1 1"  range="-60 85"/>
        <geom name="4a_left_upper_arm" fromto="0 0 0 .16 .16 -.16" size=".04 .16"/>
        <body name="4a_left_lower_arm" pos=".18 .18 -.18">
          <joint name="4a_left_elbow" axis="0 -1 -1" range="-90 50" stiffness="0"/>
          <geom name="4a_left_lower_arm" fromto=".01 -.01 .01 .17 -.17 .17" size=".031"/>
          <body name="4a_left_hand" pos=".18 -.18 .18">
            <geom name="4a_left_hand" type="sphere" size=".04" zaxis="1 -1 1"/>
          </body>
        </body>
      </body>
    </body>
    <body name="5a_torso" pos="-1 -2 1.5" childclass="body5">
      <camera name="5a_back" pos="-3 0 1" xyaxes="0 -1 0 1 0 2" mode="trackcom"/>
      <camera name="5a_side" pos="0 -3 1" xyaxes="1 0 0 0 1 2" mode="trackcom"/>
      <freejoint name="5a_root"/>
      <geom name="5a_torso" fromto="0 -.07 0 0 .07 0" size=".07"/>
      <geom name="5a_upper_waist" fromto="-.01 -.06 -.12 -.01 .06 -.12" size=".06"/>
      <body name="5a_head" pos="0 0 .19">
        <geom name="5a_head" type="sphere" size=".09"/>
        <camera name="5a_egocentric" pos=".09 0 0" xyaxes="0 -1 0 .1 0 1" fovy="80"/>
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      <body name="5a_lower_waist" pos="-.01 0 -.26">
        <geom name="5a_lower_waist" fromto="0 -.06 0 0 .06 0" size=".06"/>
        <joint name="5a_abdomen_z" pos="0 0 .065" axis="0 0 1" range="-45 45" class="big_stiff_joint"/>
        <joint name="5a_abdomen_y" pos="0 0 .065" axis="0 1 0" range="-75 30" class="big_joint"/>
        <body name="5a_pelvis" pos="0 0 -.165">
          <joint name="5a_abdomen_x" pos="0 0 .1" axis="1 0 0" range="-35 35" class="big_joint"/>
          <geom name="5a_butt" fromto="-.02 -.07 0 -.02 .07 0" size=".09"/>
          <body name="5a_right_thigh" pos="0 -.1 -.04">
            <joint name="5a_right_hip_x" axis="1 0 0" range="-25 5" class="big_joint"/>
            <joint name="5a_right_hip_z" axis="0 0 1" range="-60 35" class="big_joint"/>
            <joint name="5a_right_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="5a_right_thigh" fromto="0 0 0 0 .01 -.34" size=".06"/>
            <body name="5a_right_shin" pos="0 .01 -.403">
              <joint name="5a_right_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="5a_right_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="5a_right_foot" pos="0 0 -.39">
                <joint name="5a_right_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="5a_right_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="5a_right_right_foot" fromto="-.07 -.02 0 .14 -.04 0" size=".027"/>
                <geom name="5a_left_right_foot" fromto="-.07 0 0 .14  .02 0" size=".027"/>
              </body>
            </body>
          </body>
          <body name="5a_left_thigh" pos="0 .1 -.04">
            <joint name="5a_left_hip_x" axis="-1 0 0" range="-25 5" class="big_joint"/>
            <joint name="5a_left_hip_z" axis="0 0 -1" range="-60 35" class="big_joint"/>
            <joint name="5a_left_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="5a_left_thigh" fromto="0 0 0 0 -.01 -.34" size=".06"/>
            <body name="5a_left_shin" pos="0 -.01 -.403">
              <joint name="5a_left_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="5a_left_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="5a_left_foot" pos="0 0 -.39">
                <joint name="5a_left_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="5a_left_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="5a_left_left_foot" fromto="-.07 .02 0 .14 .04 0" size=".027"/>
                <geom name="5a_right_left_foot" fromto="-.07 0 0 .14 -.02 0" size=".027"/>
              </body>
            </body>
          </body>
        </body>
      </body>
      <body name="5a_right_upper_arm" pos="0 -.17 .06">
        <joint name="5a_right_shoulder1" axis="2 1 1"  range="-85 60"/>
        <joint name="5a_right_shoulder2" axis="0 -1 1" range="-85 60"/>
        <geom name="5a_right_upper_arm" fromto="0 0 0 .16 -.16 -.16" size=".04 .16"/>
        <body name="5a_right_lower_arm" pos=".18 -.18 -.18">
          <joint name="5a_right_elbow" axis="0 -1 1" range="-90 50" stiffness="0"/>
          <geom name="5a_right_lower_arm" fromto=".01 .01 .01 .17 .17 .17" size=".031"/>
          <body name="5a_right_hand" pos=".18 .18 .18">
            <geom name="5a_right_hand" type="sphere" size=".04" zaxis="1 1 1"/>
          </body>
        </body>
      </body>
      <body name="5a_left_upper_arm" pos="0 .17 .06">
        <joint name="5a_left_shoulder1" axis="2 -1 1" range="-60 85"/>
        <joint name="5a_left_shoulder2" axis="0 1 1"  range="-60 85"/>
        <geom name="5a_left_upper_arm" fromto="0 0 0 .16 .16 -.16" size=".04 .16"/>
        <body name="5a_left_lower_arm" pos=".18 .18 -.18">
          <joint name="5a_left_elbow" axis="0 -1 -1" range="-90 50" stiffness="0"/>
          <geom name="5a_left_lower_arm" fromto=".01 -.01 .01 .17 -.17 .17" size=".031"/>
          <body name="5a_left_hand" pos=".18 -.18 .18">
            <geom name="5a_left_hand" type="sphere" size=".04" zaxis="1 -1 1"/>
          </body>
        </body>
      </body>
    </body>
    <body name="6a_torso" pos="-1 3 1.5" childclass="body6">
      <camera name="6a_back" pos="-3 0 1" xyaxes="0 -1 0 1 0 2" mode="trackcom"/>
      <camera name="6a_side" pos="0 -3 1" xyaxes="1 0 0 0 1 2" mode="trackcom"/>
      <freejoint name="6a_root"/>
      <geom name="6a_torso" fromto="0 -.07 0 0 .07 0" size=".07"/>
      <geom name="6a_upper_waist" fromto="-.01 -.06 -.12 -.01 .06 -.12" size=".06"/>
      <body name="6a_head" pos="0 0 .19">
        <geom name="6a_head" type="sphere" size=".09"/>
        <camera name="6a_egocentric" pos=".09 0 0" xyaxes="0 -1 0 .1 0 1" fovy="80"/>
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      <body name="6a_lower_waist" pos="-.01 0 -.26">
        <geom name="6a_lower_waist" fromto="0 -.06 0 0 .06 0" size=".06"/>
        <joint name="6a_abdomen_z" pos="0 0 .065" axis="0 0 1" range="-45 45" class="big_stiff_joint"/>
        <joint name="6a_abdomen_y" pos="0 0 .065" axis="0 1 0" range="-75 30" class="big_joint"/>
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          <joint name="6a_abdomen_x" pos="0 0 .1" axis="1 0 0" range="-35 35" class="big_joint"/>
          <geom name="6a_butt" fromto="-.02 -.07 0 -.02 .07 0" size=".09"/>
          <body name="6a_right_thigh" pos="0 -.1 -.04">
            <joint name="6a_right_hip_x" axis="1 0 0" range="-25 5" class="big_joint"/>
            <joint name="6a_right_hip_z" axis="0 0 1" range="-60 35" class="big_joint"/>
            <joint name="6a_right_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="6a_right_thigh" fromto="0 0 0 0 .01 -.34" size=".06"/>
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              <joint name="6a_right_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="6a_right_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="6a_right_foot" pos="0 0 -.39">
                <joint name="6a_right_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="6a_right_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="6a_right_right_foot" fromto="-.07 -.02 0 .14 -.04 0" size=".027"/>
                <geom name="6a_left_right_foot" fromto="-.07 0 0 .14  .02 0" size=".027"/>
              </body>
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          <body name="6a_left_thigh" pos="0 .1 -.04">
            <joint name="6a_left_hip_x" axis="-1 0 0" range="-25 5" class="big_joint"/>
            <joint name="6a_left_hip_z" axis="0 0 -1" range="-60 35" class="big_joint"/>
            <joint name="6a_left_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="6a_left_thigh" fromto="0 0 0 0 -.01 -.34" size=".06"/>
            <body name="6a_left_shin" pos="0 -.01 -.403">
              <joint name="6a_left_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="6a_left_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="6a_left_foot" pos="0 0 -.39">
                <joint name="6a_left_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="6a_left_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="6a_left_left_foot" fromto="-.07 .02 0 .14 .04 0" size=".027"/>
                <geom name="6a_right_left_foot" fromto="-.07 0 0 .14 -.02 0" size=".027"/>
              </body>
            </body>
          </body>
        </body>
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      <body name="6a_right_upper_arm" pos="0 -.17 .06">
        <joint name="6a_right_shoulder1" axis="2 1 1"  range="-85 60"/>
        <joint name="6a_right_shoulder2" axis="0 -1 1" range="-85 60"/>
        <geom name="6a_right_upper_arm" fromto="0 0 0 .16 -.16 -.16" size=".04 .16"/>
        <body name="6a_right_lower_arm" pos=".18 -.18 -.18">
          <joint name="6a_right_elbow" axis="0 -1 1" range="-90 50" stiffness="0"/>
          <geom name="6a_right_lower_arm" fromto=".01 .01 .01 .17 .17 .17" size=".031"/>
          <body name="6a_right_hand" pos=".18 .18 .18">
            <geom name="6a_right_hand" type="sphere" size=".04" zaxis="1 1 1"/>
          </body>
        </body>
      </body>
      <body name="6a_left_upper_arm" pos="0 .17 .06">
        <joint name="6a_left_shoulder1" axis="2 -1 1" range="-60 85"/>
        <joint name="6a_left_shoulder2" axis="0 1 1"  range="-60 85"/>
        <geom name="6a_left_upper_arm" fromto="0 0 0 .16 .16 -.16" size=".04 .16"/>
        <body name="6a_left_lower_arm" pos=".18 .18 -.18">
          <joint name="6a_left_elbow" axis="0 -1 -1" range="-90 50" stiffness="0"/>
          <geom name="6a_left_lower_arm" fromto=".01 -.01 .01 .17 -.17 .17" size=".031"/>
          <body name="6a_left_hand" pos=".18 -.18 .18">
            <geom name="6a_left_hand" type="sphere" size=".04" zaxis="1 -1 1"/>
          </body>
        </body>
      </body>
    </body>
    <body name="7a_torso" pos="-1 -3 1.5" childclass="body7">
      <camera name="7a_back" pos="-3 0 1" xyaxes="0 -1 0 1 0 2" mode="trackcom"/>
      <camera name="7a_side" pos="0 -3 1" xyaxes="1 0 0 0 1 2" mode="trackcom"/>
      <freejoint name="7a_root"/>
      <geom name="7a_torso" fromto="0 -.07 0 0 .07 0" size=".07"/>
      <geom name="7a_upper_waist" fromto="-.01 -.06 -.12 -.01 .06 -.12" size=".06"/>
      <body name="7a_head" pos="0 0 .19">
        <geom name="7a_head" type="sphere" size=".09"/>
        <camera name="7a_egocentric" pos=".09 0 0" xyaxes="0 -1 0 .1 0 1" fovy="80"/>
      </body>
      <body name="7a_lower_waist" pos="-.01 0 -.26">
        <geom name="7a_lower_waist" fromto="0 -.06 0 0 .06 0" size=".06"/>
        <joint name="7a_abdomen_z" pos="0 0 .065" axis="0 0 1" range="-45 45" class="big_stiff_joint"/>
        <joint name="7a_abdomen_y" pos="0 0 .065" axis="0 1 0" range="-75 30" class="big_joint"/>
        <body name="7a_pelvis" pos="0 0 -.165">
          <joint name="7a_abdomen_x" pos="0 0 .1" axis="1 0 0" range="-35 35" class="big_joint"/>
          <geom name="7a_butt" fromto="-.02 -.07 0 -.02 .07 0" size=".09"/>
          <body name="7a_right_thigh" pos="0 -.1 -.04">
            <joint name="7a_right_hip_x" axis="1 0 0" range="-25 5" class="big_joint"/>
            <joint name="7a_right_hip_z" axis="0 0 1" range="-60 35" class="big_joint"/>
            <joint name="7a_right_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="7a_right_thigh" fromto="0 0 0 0 .01 -.34" size=".06"/>
            <body name="7a_right_shin" pos="0 .01 -.403">
              <joint name="7a_right_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="7a_right_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="7a_right_foot" pos="0 0 -.39">
                <joint name="7a_right_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="7a_right_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="7a_right_right_foot" fromto="-.07 -.02 0 .14 -.04 0" size=".027"/>
                <geom name="7a_left_right_foot" fromto="-.07 0 0 .14  .02 0" size=".027"/>
              </body>
            </body>
          </body>
          <body name="7a_left_thigh" pos="0 .1 -.04">
            <joint name="7a_left_hip_x" axis="-1 0 0" range="-25 5" class="big_joint"/>
            <joint name="7a_left_hip_z" axis="0 0 -1" range="-60 35" class="big_joint"/>
            <joint name="7a_left_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="7a_left_thigh" fromto="0 0 0 0 -.01 -.34" size=".06"/>
            <body name="7a_left_shin" pos="0 -.01 -.403">
              <joint name="7a_left_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="7a_left_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="7a_left_foot" pos="0 0 -.39">
                <joint name="7a_left_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="7a_left_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="7a_left_left_foot" fromto="-.07 .02 0 .14 .04 0" size=".027"/>
                <geom name="7a_right_left_foot" fromto="-.07 0 0 .14 -.02 0" size=".027"/>
              </body>
            </body>
          </body>
        </body>
      </body>
      <body name="7a_right_upper_arm" pos="0 -.17 .06">
        <joint name="7a_right_shoulder1" axis="2 1 1"  range="-85 60"/>
        <joint name="7a_right_shoulder2" axis="0 -1 1" range="-85 60"/>
        <geom name="7a_right_upper_arm" fromto="0 0 0 .16 -.16 -.16" size=".04 .16"/>
        <body name="7a_right_lower_arm" pos=".18 -.18 -.18">
          <joint name="7a_right_elbow" axis="0 -1 1" range="-90 50" stiffness="0"/>
          <geom name="7a_right_lower_arm" fromto=".01 .01 .01 .17 .17 .17" size=".031"/>
          <body name="7a_right_hand" pos=".18 .18 .18">
            <geom name="7a_right_hand" type="sphere" size=".04" zaxis="1 1 1"/>
          </body>
        </body>
      </body>
      <body name="7a_left_upper_arm" pos="0 .17 .06">
        <joint name="7a_left_shoulder1" axis="2 -1 1" range="-60 85"/>
        <joint name="7a_left_shoulder2" axis="0 1 1"  range="-60 85"/>
        <geom name="7a_left_upper_arm" fromto="0 0 0 .16 .16 -.16" size=".04 .16"/>
        <body name="7a_left_lower_arm" pos=".18 .18 -.18">
          <joint name="7a_left_elbow" axis="0 -1 -1" range="-90 50" stiffness="0"/>
          <geom name="7a_left_lower_arm" fromto=".01 -.01 .01 .17 -.17 .17" size=".031"/>
          <body name="7a_left_hand" pos=".18 -.18 .18">
            <geom name="7a_left_hand" type="sphere" size=".04" zaxis="1 -1 1"/>
          </body>
        </body>
      </body>
    </body>
  </worldbody>
  <actuator>
    <motor gear="40"  joint="1a_abdomen_y"/>
    <motor gear="40"  joint="1a_abdomen_z"/>
    <motor gear="40"  joint="1a_abdomen_x"/>
    <motor gear="40"  joint="1a_right_hip_x"/>
    <motor gear="40"  joint="1a_right_hip_z"/>
    <motor gear="120" joint="1a_right_hip_y"/>
    <motor gear="80"  joint="1a_right_knee"/>
    <motor gear="20"  joint="1a_right_ankle_x"/>
    <motor gear="20"  joint="1a_right_ankle_y"/>
    <motor gear="40"  joint="1a_left_hip_x"/>
    <motor gear="40"  joint="1a_left_hip_z"/>
    <motor gear="120" joint="1a_left_hip_y"/>
    <motor gear="80"  joint="1a_left_knee"/>
    <motor gear="20"  joint="1a_left_ankle_x"/>
    <motor gear="20"  joint="1a_left_ankle_y"/>
    <motor gear="20"  joint="1a_right_shoulder1"/>
    <motor gear="20"  joint="1a_right_shoulder2"/>
    <motor gear="40"  joint="1a_right_elbow"/>
    <motor gear="20"  joint="1a_left_shoulder1"/>
    <motor gear="20"  joint="1a_left_shoulder2"/>
    <motor gear="40"  joint="1a_left_elbow"/>
  </actuator>
  <actuator>
    <motor gear="40"  joint="2a_abdomen_y"/>
    <motor gear="40"  joint="2a_abdomen_z"/>
    <motor gear="40"  joint="2a_abdomen_x"/>
    <motor gear="40"  joint="2a_right_hip_x"/>
    <motor gear="40"  joint="2a_right_hip_z"/>
    <motor gear="120" joint="2a_right_hip_y"/>
    <motor gear="80"  joint="2a_right_knee"/>
    <motor gear="20"  joint="2a_right_ankle_x"/>
    <motor gear="20"  joint="2a_right_ankle_y"/>
    <motor gear="40"  joint="2a_left_hip_x"/>
    <motor gear="40"  joint="2a_left_hip_z"/>
    <motor gear="120" joint="2a_left_hip_y"/>
    <motor gear="80"  joint="2a_left_knee"/>
    <motor gear="20"  joint="2a_left_ankle_x"/>
    <motor gear="20"  joint="2a_left_ankle_y"/>
    <motor gear="20"  joint="2a_right_shoulder1"/>
    <motor gear="20"  joint="2a_right_shoulder2"/>
    <motor gear="40"  joint="2a_right_elbow"/>
    <motor gear="20"  joint="2a_left_shoulder1"/>
    <motor gear="20"  joint="2a_left_shoulder2"/>
    <motor gear="40"  joint="2a_left_elbow"/>
  </actuator>
  <actuator>
    <motor gear="40"  joint="3a_abdomen_y"/>
    <motor gear="40"  joint="3a_abdomen_z"/>
    <motor gear="40"  joint="3a_abdomen_x"/>
    <motor gear="40"  joint="3a_right_hip_x"/>
    <motor gear="40"  joint="3a_right_hip_z"/>
    <motor gear="120" joint="3a_right_hip_y"/>
    <motor gear="80"  joint="3a_right_knee"/>
    <motor gear="20"  joint="3a_right_ankle_x"/>
    <motor gear="20"  joint="3a_right_ankle_y"/>
    <motor gear="40"  joint="3a_left_hip_x"/>
    <motor gear="40"  joint="3a_left_hip_z"/>
    <motor gear="120" joint="3a_left_hip_y"/>
    <motor gear="80"  joint="3a_left_knee"/>
    <motor gear="20"  joint="3a_left_ankle_x"/>
    <motor gear="20"  joint="3a_left_ankle_y"/>
    <motor gear="20"  joint="3a_right_shoulder1"/>
    <motor gear="20"  joint="3a_right_shoulder2"/>
    <motor gear="40"  joint="3a_right_elbow"/>
    <motor gear="20"  joint="3a_left_shoulder1"/>
    <motor gear="20"  joint="3a_left_shoulder2"/>
    <motor gear="40"  joint="3a_left_elbow"/>
  </actuator>
  <actuator>
    <motor gear="40"  joint="4a_abdomen_y"/>
    <motor gear="40"  joint="4a_abdomen_z"/>
    <motor gear="40"  joint="4a_abdomen_x"/>
    <motor gear="40"  joint="4a_right_hip_x"/>
    <motor gear="40"  joint="4a_right_hip_z"/>
    <motor gear="120" joint="4a_right_hip_y"/>
    <motor gear="80"  joint="4a_right_knee"/>
    <motor gear="20"  joint="4a_right_ankle_x"/>
    <motor gear="20"  joint="4a_right_ankle_y"/>
    <motor gear="40"  joint="4a_left_hip_x"/>
    <motor gear="40"  joint="4a_left_hip_z"/>
    <motor gear="120" joint="4a_left_hip_y"/>
    <motor gear="80"  joint="4a_left_knee"/>
    <motor gear="20"  joint="4a_left_ankle_x"/>
    <motor gear="20"  joint="4a_left_ankle_y"/>
    <motor gear="20"  joint="4a_right_shoulder1"/>
    <motor gear="20"  joint="4a_right_shoulder2"/>
    <motor gear="40"  joint="4a_right_elbow"/>
    <motor gear="20"  joint="4a_left_shoulder1"/>
    <motor gear="20"  joint="4a_left_shoulder2"/>
    <motor gear="40"  joint="4a_left_elbow"/>
  </actuator>
  <actuator>
    <motor gear="40"  joint="5a_abdomen_y"/>
    <motor gear="40"  joint="5a_abdomen_z"/>
    <motor gear="40"  joint="5a_abdomen_x"/>
    <motor gear="40"  joint="5a_right_hip_x"/>
    <motor gear="40"  joint="5a_right_hip_z"/>
    <motor gear="120" joint="5a_right_hip_y"/>
    <motor gear="80"  joint="5a_right_knee"/>
    <motor gear="20"  joint="5a_right_ankle_x"/>
    <motor gear="20"  joint="5a_right_ankle_y"/>
    <motor gear="40"  joint="5a_left_hip_x"/>
    <motor gear="40"  joint="5a_left_hip_z"/>
    <motor gear="120" joint="5a_left_hip_y"/>
    <motor gear="80"  joint="5a_left_knee"/>
    <motor gear="20"  joint="5a_left_ankle_x"/>
    <motor gear="20"  joint="5a_left_ankle_y"/>
    <motor gear="20"  joint="5a_right_shoulder1"/>
    <motor gear="20"  joint="5a_right_shoulder2"/>
    <motor gear="40"  joint="5a_right_elbow"/>
    <motor gear="20"  joint="5a_left_shoulder1"/>
    <motor gear="20"  joint="5a_left_shoulder2"/>
    <motor gear="40"  joint="5a_left_elbow"/>
  </actuator>
  <actuator>
    <motor gear="40"  joint="6a_abdomen_y"/>
    <motor gear="40"  joint="6a_abdomen_z"/>
    <motor gear="40"  joint="6a_abdomen_x"/>
    <motor gear="40"  joint="6a_right_hip_x"/>
    <motor gear="40"  joint="6a_right_hip_z"/>
    <motor gear="120" joint="6a_right_hip_y"/>
    <motor gear="80"  joint="6a_right_knee"/>
    <motor gear="20"  joint="6a_right_ankle_x"/>
    <motor gear="20"  joint="6a_right_ankle_y"/>
    <motor gear="40"  joint="6a_left_hip_x"/>
    <motor gear="40"  joint="6a_left_hip_z"/>
    <motor gear="120" joint="6a_left_hip_y"/>
    <motor gear="80"  joint="6a_left_knee"/>
    <motor gear="20"  joint="6a_left_ankle_x"/>
    <motor gear="20"  joint="6a_left_ankle_y"/>
    <motor gear="20"  joint="6a_right_shoulder1"/>
    <motor gear="20"  joint="6a_right_shoulder2"/>
    <motor gear="40"  joint="6a_right_elbow"/>
    <motor gear="20"  joint="6a_left_shoulder1"/>
    <motor gear="20"  joint="6a_left_shoulder2"/>
    <motor gear="40"  joint="6a_left_elbow"/>
  </actuator>
  <actuator>
    <motor gear="40"  joint="7a_abdomen_y"/>
    <motor gear="40"  joint="7a_abdomen_z"/>
    <motor gear="40"  joint="7a_abdomen_x"/>
    <motor gear="40"  joint="7a_right_hip_x"/>
    <motor gear="40"  joint="7a_right_hip_z"/>
    <motor gear="120" joint="7a_right_hip_y"/>
    <motor gear="80"  joint="7a_right_knee"/>
    <motor gear="20"  joint="7a_right_ankle_x"/>
    <motor gear="20"  joint="7a_right_ankle_y"/>
    <motor gear="40"  joint="7a_left_hip_x"/>
    <motor gear="40"  joint="7a_left_hip_z"/>
    <motor gear="120" joint="7a_left_hip_y"/>
    <motor gear="80"  joint="7a_left_knee"/>
    <motor gear="20"  joint="7a_left_ankle_x"/>
    <motor gear="20"  joint="7a_left_ankle_y"/>
    <motor gear="20"  joint="7a_right_shoulder1"/>
    <motor gear="20"  joint="7a_right_shoulder2"/>
    <motor gear="40"  joint="7a_right_elbow"/>
    <motor gear="20"  joint="7a_left_shoulder1"/>
    <motor gear="20"  joint="7a_left_shoulder2"/>
    <motor gear="40"  joint="7a_left_elbow"/>
  </actuator>
 </mujoco>
@@ -0,0 +1,879 @@
 <mujoco model="08 Humanoids">
  <option timestep="0.005" solver="Newton" iterations="1" ls_iterations="4">
    <flag eulerdamp="disable"/>
  </option>
  <custom>
    <numeric data="32" name="max_contact_points"/>
    <numeric data="32" name="max_geom_pairs"/>
  </custom>
  <size memory="100M"/>
  <asset>
    <texture type="skybox" builtin="gradient" rgb1=".3 .5 .7" rgb2="0 0 0" width="512" height="512"/>
    <texture name="body" type="cube" builtin="flat" mark="cross" width="128" height="128"
             rgb1="0.8 0.6 0.4" rgb2="0.8 0.6 0.4" markrgb="1 1 1" random="0.01"/>
    <material name="body" texture="body" texuniform="true" rgba="0.8 0.6 .4 1"/>
    <texture name="grid" type="2d" builtin="checker" width="512" height="512" rgb1=".1 .2 .3" rgb2=".2 .3 .4"/>
    <material name="grid" texture="grid" texrepeat="1 1" texuniform="true" reflectance=".2"/>
  </asset>
  <default>
    <motor ctrlrange="-1 1" ctrllimited="true"/>
    <joint type="hinge" damping=".2" stiffness="1" armature=".01" limited="true" solimplimit="0 .99 .01"/>
    <default class="big_joint">
      <joint damping="5" stiffness="10"/>
      <default class="big_stiff_joint">
        <joint stiffness="20"/>
      </default>
    </default>
    <default class="body1">
      <geom type="capsule" condim="3" friction=".7" solimp=".9 .99 .003" solref=".015 1" material="body" contype="2" conaffinity="509"/>
    </default>
    <default class="body2">
      <geom type="capsule" condim="3" friction=".7" solimp=".9 .99 .003" solref=".015 1" material="body" contype="4" conaffinity="507"/>
    </default>
    <default class="body3">
      <geom type="capsule" condim="3" friction=".7" solimp=".9 .99 .003" solref=".015 1" material="body" contype="8" conaffinity="503"/>
    </default>
    <default class="body4">
      <geom type="capsule" condim="3" friction=".7" solimp=".9 .99 .003" solref=".015 1" material="body" contype="16" conaffinity="495"/>
    </default>
    <default class="body5">
      <geom type="capsule" condim="3" friction=".7" solimp=".9 .99 .003" solref=".015 1" material="body" contype="32" conaffinity="479"/>
    </default>
    <default class="body6">
      <geom type="capsule" condim="3" friction=".7" solimp=".9 .99 .003" solref=".015 1" material="body" contype="64" conaffinity="447"/>
    </default>
    <default class="body7">
      <geom type="capsule" condim="3" friction=".7" solimp=".9 .99 .003" solref=".015 1" material="body" contype="128" conaffinity="383"/>
    </default>
    <default class="body8">
      <geom type="capsule" condim="3" friction=".7" solimp=".9 .99 .003" solref=".015 1" material="body" contype="256" conaffinity="255"/>
    </default>
  </default>
  <visual>
    <map force="0.1" zfar="30"/>
    <rgba haze="0.15 0.25 0.35 1"/>
    <quality shadowsize="4096"/>
    <global offwidth="800" offheight="800"/>
  </visual>
  <worldbody>
    <geom size="10 10 .05" type="plane" material="grid" condim="3"/>
    <light dir=".2 1 -.4" diffuse=".8 .8 .8" specular="0.3 0.3 0.3" pos="-2 -10 4" cutoff="35"/>
    <light dir="-.2 1 -.4" diffuse=".8 .8 .8" specular="0.3 0.3 0.3" pos="2 -10 4" cutoff="35"/>
    <body name="1a_torso" pos="-1 0 1.5" childclass="body1">
      <camera name="1a_back" pos="-3 0 1" xyaxes="0 -1 0 1 0 2" mode="trackcom"/>
      <camera name="1a_side" pos="0 -3 1" xyaxes="1 0 0 0 1 2" mode="trackcom"/>
      <freejoint name="1a_root"/>
      <geom name="1a_torso" fromto="0 -.07 0 0 .07 0" size=".07"/>
      <geom name="1a_upper_waist" fromto="-.01 -.06 -.12 -.01 .06 -.12" size=".06"/>
      <body name="1a_head" pos="0 0 .19">
        <geom name="1a_head" type="sphere" size=".09"/>
        <camera name="1a_egocentric" pos=".09 0 0" xyaxes="0 -1 0 .1 0 1" fovy="80"/>
      </body>
      <body name="1a_lower_waist" pos="-.01 0 -.26">
        <geom name="1a_lower_waist" fromto="0 -.06 0 0 .06 0" size=".06"/>
        <joint name="1a_abdomen_z" pos="0 0 .065" axis="0 0 1" range="-45 45" class="big_stiff_joint"/>
        <joint name="1a_abdomen_y" pos="0 0 .065" axis="0 1 0" range="-75 30" class="big_joint"/>
        <body name="1a_pelvis" pos="0 0 -.165">
          <joint name="1a_abdomen_x" pos="0 0 .1" axis="1 0 0" range="-35 35" class="big_joint"/>
          <geom name="1a_butt" fromto="-.02 -.07 0 -.02 .07 0" size=".09"/>
          <body name="1a_right_thigh" pos="0 -.1 -.04">
            <joint name="1a_right_hip_x" axis="1 0 0" range="-25 5" class="big_joint"/>
            <joint name="1a_right_hip_z" axis="0 0 1" range="-60 35" class="big_joint"/>
            <joint name="1a_right_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="1a_right_thigh" fromto="0 0 0 0 .01 -.34" size=".06"/>
            <body name="1a_right_shin" pos="0 .01 -.403">
              <joint name="1a_right_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="1a_right_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="1a_right_foot" pos="0 0 -.39">
                <joint name="1a_right_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="1a_right_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="1a_right_right_foot" fromto="-.07 -.02 0 .14 -.04 0" size=".027"/>
                <geom name="1a_left_right_foot" fromto="-.07 0 0 .14  .02 0" size=".027"/>
              </body>
            </body>
          </body>
          <body name="1a_left_thigh" pos="0 .1 -.04">
            <joint name="1a_left_hip_x" axis="-1 0 0" range="-25 5" class="big_joint"/>
            <joint name="1a_left_hip_z" axis="0 0 -1" range="-60 35" class="big_joint"/>
            <joint name="1a_left_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="1a_left_thigh" fromto="0 0 0 0 -.01 -.34" size=".06"/>
            <body name="1a_left_shin" pos="0 -.01 -.403">
              <joint name="1a_left_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="1a_left_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="1a_left_foot" pos="0 0 -.39">
                <joint name="1a_left_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="1a_left_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="1a_left_left_foot" fromto="-.07 .02 0 .14 .04 0" size=".027"/>
                <geom name="1a_right_left_foot" fromto="-.07 0 0 .14 -.02 0" size=".027"/>
              </body>
            </body>
          </body>
        </body>
      </body>
      <body name="1a_right_upper_arm" pos="0 -.17 .06">
        <joint name="1a_right_shoulder1" axis="2 1 1"  range="-85 60"/>
        <joint name="1a_right_shoulder2" axis="0 -1 1" range="-85 60"/>
        <geom name="1a_right_upper_arm" fromto="0 0 0 .16 -.16 -.16" size=".04 .16"/>
        <body name="1a_right_lower_arm" pos=".18 -.18 -.18">
          <joint name="1a_right_elbow" axis="0 -1 1" range="-90 50" stiffness="0"/>
          <geom name="1a_right_lower_arm" fromto=".01 .01 .01 .17 .17 .17" size=".031"/>
          <body name="1a_right_hand" pos=".18 .18 .18">
            <geom name="1a_right_hand" type="sphere" size=".04" zaxis="1 1 1"/>
          </body>
        </body>
      </body>
      <body name="1a_left_upper_arm" pos="0 .17 .06">
        <joint name="1a_left_shoulder1" axis="2 -1 1" range="-60 85"/>
        <joint name="1a_left_shoulder2" axis="0 1 1"  range="-60 85"/>
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        <body name="1a_left_lower_arm" pos=".18 .18 -.18">
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          <geom name="1a_left_lower_arm" fromto=".01 -.01 .01 .17 -.17 .17" size=".031"/>
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          </body>
        </body>
      </body>
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      <camera name="2a_back" pos="-3 0 1" xyaxes="0 -1 0 1 0 2" mode="trackcom"/>
      <camera name="2a_side" pos="0 -3 1" xyaxes="1 0 0 0 1 2" mode="trackcom"/>
      <freejoint name="2a_root"/>
      <geom name="2a_torso" fromto="0 -.07 0 0 .07 0" size=".07"/>
      <geom name="2a_upper_waist" fromto="-.01 -.06 -.12 -.01 .06 -.12" size=".06"/>
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        <geom name="2a_head" type="sphere" size=".09"/>
        <camera name="2a_egocentric" pos=".09 0 0" xyaxes="0 -1 0 .1 0 1" fovy="80"/>
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      <body name="2a_lower_waist" pos="-.01 0 -.26">
        <geom name="2a_lower_waist" fromto="0 -.06 0 0 .06 0" size=".06"/>
        <joint name="2a_abdomen_z" pos="0 0 .065" axis="0 0 1" range="-45 45" class="big_stiff_joint"/>
        <joint name="2a_abdomen_y" pos="0 0 .065" axis="0 1 0" range="-75 30" class="big_joint"/>
        <body name="2a_pelvis" pos="0 0 -.165">
          <joint name="2a_abdomen_x" pos="0 0 .1" axis="1 0 0" range="-35 35" class="big_joint"/>
          <geom name="2a_butt" fromto="-.02 -.07 0 -.02 .07 0" size=".09"/>
          <body name="2a_right_thigh" pos="0 -.1 -.04">
            <joint name="2a_right_hip_x" axis="1 0 0" range="-25 5" class="big_joint"/>
            <joint name="2a_right_hip_z" axis="0 0 1" range="-60 35" class="big_joint"/>
            <joint name="2a_right_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="2a_right_thigh" fromto="0 0 0 0 .01 -.34" size=".06"/>
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              <joint name="2a_right_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="2a_right_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="2a_right_foot" pos="0 0 -.39">
                <joint name="2a_right_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="2a_right_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="2a_right_right_foot" fromto="-.07 -.02 0 .14 -.04 0" size=".027"/>
                <geom name="2a_left_right_foot" fromto="-.07 0 0 .14  .02 0" size=".027"/>
              </body>
            </body>
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            <joint name="2a_left_hip_x" axis="-1 0 0" range="-25 5" class="big_joint"/>
            <joint name="2a_left_hip_z" axis="0 0 -1" range="-60 35" class="big_joint"/>
            <joint name="2a_left_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="2a_left_thigh" fromto="0 0 0 0 -.01 -.34" size=".06"/>
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              <joint name="2a_left_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="2a_left_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="2a_left_foot" pos="0 0 -.39">
                <joint name="2a_left_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="2a_left_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="2a_left_left_foot" fromto="-.07 .02 0 .14 .04 0" size=".027"/>
                <geom name="2a_right_left_foot" fromto="-.07 0 0 .14 -.02 0" size=".027"/>
              </body>
            </body>
          </body>
        </body>
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      <body name="2a_right_upper_arm" pos="0 -.17 .06">
        <joint name="2a_right_shoulder1" axis="2 1 1"  range="-85 60"/>
        <joint name="2a_right_shoulder2" axis="0 -1 1" range="-85 60"/>
        <geom name="2a_right_upper_arm" fromto="0 0 0 .16 -.16 -.16" size=".04 .16"/>
        <body name="2a_right_lower_arm" pos=".18 -.18 -.18">
          <joint name="2a_right_elbow" axis="0 -1 1" range="-90 50" stiffness="0"/>
          <geom name="2a_right_lower_arm" fromto=".01 .01 .01 .17 .17 .17" size=".031"/>
          <body name="2a_right_hand" pos=".18 .18 .18">
            <geom name="2a_right_hand" type="sphere" size=".04" zaxis="1 1 1"/>
          </body>
        </body>
      </body>
      <body name="2a_left_upper_arm" pos="0 .17 .06">
        <joint name="2a_left_shoulder1" axis="2 -1 1" range="-60 85"/>
        <joint name="2a_left_shoulder2" axis="0 1 1"  range="-60 85"/>
        <geom name="2a_left_upper_arm" fromto="0 0 0 .16 .16 -.16" size=".04 .16"/>
        <body name="2a_left_lower_arm" pos=".18 .18 -.18">
          <joint name="2a_left_elbow" axis="0 -1 -1" range="-90 50" stiffness="0"/>
          <geom name="2a_left_lower_arm" fromto=".01 -.01 .01 .17 -.17 .17" size=".031"/>
          <body name="2a_left_hand" pos=".18 -.18 .18">
            <geom name="2a_left_hand" type="sphere" size=".04" zaxis="1 -1 1"/>
          </body>
        </body>
      </body>
    </body>
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      <camera name="3a_back" pos="-3 0 1" xyaxes="0 -1 0 1 0 2" mode="trackcom"/>
      <camera name="3a_side" pos="0 -3 1" xyaxes="1 0 0 0 1 2" mode="trackcom"/>
      <freejoint name="3a_root"/>
      <geom name="3a_torso" fromto="0 -.07 0 0 .07 0" size=".07"/>
      <geom name="3a_upper_waist" fromto="-.01 -.06 -.12 -.01 .06 -.12" size=".06"/>
      <body name="3a_head" pos="0 0 .19">
        <geom name="3a_head" type="sphere" size=".09"/>
        <camera name="3a_egocentric" pos=".09 0 0" xyaxes="0 -1 0 .1 0 1" fovy="80"/>
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      <body name="3a_lower_waist" pos="-.01 0 -.26">
        <geom name="3a_lower_waist" fromto="0 -.06 0 0 .06 0" size=".06"/>
        <joint name="3a_abdomen_z" pos="0 0 .065" axis="0 0 1" range="-45 45" class="big_stiff_joint"/>
        <joint name="3a_abdomen_y" pos="0 0 .065" axis="0 1 0" range="-75 30" class="big_joint"/>
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          <body name="3a_right_thigh" pos="0 -.1 -.04">
            <joint name="3a_right_hip_x" axis="1 0 0" range="-25 5" class="big_joint"/>
            <joint name="3a_right_hip_z" axis="0 0 1" range="-60 35" class="big_joint"/>
            <joint name="3a_right_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="3a_right_thigh" fromto="0 0 0 0 .01 -.34" size=".06"/>
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              <joint name="3a_right_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="3a_right_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="3a_right_foot" pos="0 0 -.39">
                <joint name="3a_right_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="3a_right_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="3a_right_right_foot" fromto="-.07 -.02 0 .14 -.04 0" size=".027"/>
                <geom name="3a_left_right_foot" fromto="-.07 0 0 .14  .02 0" size=".027"/>
              </body>
            </body>
          </body>
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            <joint name="3a_left_hip_x" axis="-1 0 0" range="-25 5" class="big_joint"/>
            <joint name="3a_left_hip_z" axis="0 0 -1" range="-60 35" class="big_joint"/>
            <joint name="3a_left_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="3a_left_thigh" fromto="0 0 0 0 -.01 -.34" size=".06"/>
            <body name="3a_left_shin" pos="0 -.01 -.403">
              <joint name="3a_left_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="3a_left_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="3a_left_foot" pos="0 0 -.39">
                <joint name="3a_left_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="3a_left_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="3a_left_left_foot" fromto="-.07 .02 0 .14 .04 0" size=".027"/>
                <geom name="3a_right_left_foot" fromto="-.07 0 0 .14 -.02 0" size=".027"/>
              </body>
            </body>
          </body>
        </body>
      </body>
      <body name="3a_right_upper_arm" pos="0 -.17 .06">
        <joint name="3a_right_shoulder1" axis="2 1 1"  range="-85 60"/>
        <joint name="3a_right_shoulder2" axis="0 -1 1" range="-85 60"/>
        <geom name="3a_right_upper_arm" fromto="0 0 0 .16 -.16 -.16" size=".04 .16"/>
        <body name="3a_right_lower_arm" pos=".18 -.18 -.18">
          <joint name="3a_right_elbow" axis="0 -1 1" range="-90 50" stiffness="0"/>
          <geom name="3a_right_lower_arm" fromto=".01 .01 .01 .17 .17 .17" size=".031"/>
          <body name="3a_right_hand" pos=".18 .18 .18">
            <geom name="3a_right_hand" type="sphere" size=".04" zaxis="1 1 1"/>
          </body>
        </body>
      </body>
      <body name="3a_left_upper_arm" pos="0 .17 .06">
        <joint name="3a_left_shoulder1" axis="2 -1 1" range="-60 85"/>
        <joint name="3a_left_shoulder2" axis="0 1 1"  range="-60 85"/>
        <geom name="3a_left_upper_arm" fromto="0 0 0 .16 .16 -.16" size=".04 .16"/>
        <body name="3a_left_lower_arm" pos=".18 .18 -.18">
          <joint name="3a_left_elbow" axis="0 -1 -1" range="-90 50" stiffness="0"/>
          <geom name="3a_left_lower_arm" fromto=".01 -.01 .01 .17 -.17 .17" size=".031"/>
          <body name="3a_left_hand" pos=".18 -.18 .18">
            <geom name="3a_left_hand" type="sphere" size=".04" zaxis="1 -1 1"/>
          </body>
        </body>
      </body>
    </body>
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      <camera name="4a_back" pos="-3 0 1" xyaxes="0 -1 0 1 0 2" mode="trackcom"/>
      <camera name="4a_side" pos="0 -3 1" xyaxes="1 0 0 0 1 2" mode="trackcom"/>
      <freejoint name="4a_root"/>
      <geom name="4a_torso" fromto="0 -.07 0 0 .07 0" size=".07"/>
      <geom name="4a_upper_waist" fromto="-.01 -.06 -.12 -.01 .06 -.12" size=".06"/>
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        <geom name="4a_head" type="sphere" size=".09"/>
        <camera name="4a_egocentric" pos=".09 0 0" xyaxes="0 -1 0 .1 0 1" fovy="80"/>
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      <body name="4a_lower_waist" pos="-.01 0 -.26">
        <geom name="4a_lower_waist" fromto="0 -.06 0 0 .06 0" size=".06"/>
        <joint name="4a_abdomen_z" pos="0 0 .065" axis="0 0 1" range="-45 45" class="big_stiff_joint"/>
        <joint name="4a_abdomen_y" pos="0 0 .065" axis="0 1 0" range="-75 30" class="big_joint"/>
        <body name="4a_pelvis" pos="0 0 -.165">
          <joint name="4a_abdomen_x" pos="0 0 .1" axis="1 0 0" range="-35 35" class="big_joint"/>
          <geom name="4a_butt" fromto="-.02 -.07 0 -.02 .07 0" size=".09"/>
          <body name="4a_right_thigh" pos="0 -.1 -.04">
            <joint name="4a_right_hip_x" axis="1 0 0" range="-25 5" class="big_joint"/>
            <joint name="4a_right_hip_z" axis="0 0 1" range="-60 35" class="big_joint"/>
            <joint name="4a_right_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="4a_right_thigh" fromto="0 0 0 0 .01 -.34" size=".06"/>
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              <joint name="4a_right_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="4a_right_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="4a_right_foot" pos="0 0 -.39">
                <joint name="4a_right_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="4a_right_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="4a_right_right_foot" fromto="-.07 -.02 0 .14 -.04 0" size=".027"/>
                <geom name="4a_left_right_foot" fromto="-.07 0 0 .14  .02 0" size=".027"/>
              </body>
            </body>
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            <joint name="4a_left_hip_x" axis="-1 0 0" range="-25 5" class="big_joint"/>
            <joint name="4a_left_hip_z" axis="0 0 -1" range="-60 35" class="big_joint"/>
            <joint name="4a_left_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="4a_left_thigh" fromto="0 0 0 0 -.01 -.34" size=".06"/>
            <body name="4a_left_shin" pos="0 -.01 -.403">
              <joint name="4a_left_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="4a_left_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="4a_left_foot" pos="0 0 -.39">
                <joint name="4a_left_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="4a_left_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="4a_left_left_foot" fromto="-.07 .02 0 .14 .04 0" size=".027"/>
                <geom name="4a_right_left_foot" fromto="-.07 0 0 .14 -.02 0" size=".027"/>
              </body>
            </body>
          </body>
        </body>
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      <body name="4a_right_upper_arm" pos="0 -.17 .06">
        <joint name="4a_right_shoulder1" axis="2 1 1"  range="-85 60"/>
        <joint name="4a_right_shoulder2" axis="0 -1 1" range="-85 60"/>
        <geom name="4a_right_upper_arm" fromto="0 0 0 .16 -.16 -.16" size=".04 .16"/>
        <body name="4a_right_lower_arm" pos=".18 -.18 -.18">
          <joint name="4a_right_elbow" axis="0 -1 1" range="-90 50" stiffness="0"/>
          <geom name="4a_right_lower_arm" fromto=".01 .01 .01 .17 .17 .17" size=".031"/>
          <body name="4a_right_hand" pos=".18 .18 .18">
            <geom name="4a_right_hand" type="sphere" size=".04" zaxis="1 1 1"/>
          </body>
        </body>
      </body>
      <body name="4a_left_upper_arm" pos="0 .17 .06">
        <joint name="4a_left_shoulder1" axis="2 -1 1" range="-60 85"/>
        <joint name="4a_left_shoulder2" axis="0 1 1"  range="-60 85"/>
        <geom name="4a_left_upper_arm" fromto="0 0 0 .16 .16 -.16" size=".04 .16"/>
        <body name="4a_left_lower_arm" pos=".18 .18 -.18">
          <joint name="4a_left_elbow" axis="0 -1 -1" range="-90 50" stiffness="0"/>
          <geom name="4a_left_lower_arm" fromto=".01 -.01 .01 .17 -.17 .17" size=".031"/>
          <body name="4a_left_hand" pos=".18 -.18 .18">
            <geom name="4a_left_hand" type="sphere" size=".04" zaxis="1 -1 1"/>
          </body>
        </body>
      </body>
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      <camera name="5a_back" pos="-3 0 1" xyaxes="0 -1 0 1 0 2" mode="trackcom"/>
      <camera name="5a_side" pos="0 -3 1" xyaxes="1 0 0 0 1 2" mode="trackcom"/>
      <freejoint name="5a_root"/>
      <geom name="5a_torso" fromto="0 -.07 0 0 .07 0" size=".07"/>
      <geom name="5a_upper_waist" fromto="-.01 -.06 -.12 -.01 .06 -.12" size=".06"/>
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        <geom name="5a_head" type="sphere" size=".09"/>
        <camera name="5a_egocentric" pos=".09 0 0" xyaxes="0 -1 0 .1 0 1" fovy="80"/>
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      <body name="5a_lower_waist" pos="-.01 0 -.26">
        <geom name="5a_lower_waist" fromto="0 -.06 0 0 .06 0" size=".06"/>
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        <joint name="5a_abdomen_y" pos="0 0 .065" axis="0 1 0" range="-75 30" class="big_joint"/>
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          <body name="5a_right_thigh" pos="0 -.1 -.04">
            <joint name="5a_right_hip_x" axis="1 0 0" range="-25 5" class="big_joint"/>
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            <joint name="5a_right_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="5a_right_thigh" fromto="0 0 0 0 .01 -.34" size=".06"/>
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              <joint name="5a_right_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="5a_right_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="5a_right_foot" pos="0 0 -.39">
                <joint name="5a_right_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="5a_right_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="5a_right_right_foot" fromto="-.07 -.02 0 .14 -.04 0" size=".027"/>
                <geom name="5a_left_right_foot" fromto="-.07 0 0 .14  .02 0" size=".027"/>
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            <joint name="5a_left_hip_z" axis="0 0 -1" range="-60 35" class="big_joint"/>
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              <joint name="5a_left_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="5a_left_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="5a_left_foot" pos="0 0 -.39">
                <joint name="5a_left_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="5a_left_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="5a_left_left_foot" fromto="-.07 .02 0 .14 .04 0" size=".027"/>
                <geom name="5a_right_left_foot" fromto="-.07 0 0 .14 -.02 0" size=".027"/>
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            </body>
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        </body>
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      <body name="5a_right_upper_arm" pos="0 -.17 .06">
        <joint name="5a_right_shoulder1" axis="2 1 1"  range="-85 60"/>
        <joint name="5a_right_shoulder2" axis="0 -1 1" range="-85 60"/>
        <geom name="5a_right_upper_arm" fromto="0 0 0 .16 -.16 -.16" size=".04 .16"/>
        <body name="5a_right_lower_arm" pos=".18 -.18 -.18">
          <joint name="5a_right_elbow" axis="0 -1 1" range="-90 50" stiffness="0"/>
          <geom name="5a_right_lower_arm" fromto=".01 .01 .01 .17 .17 .17" size=".031"/>
          <body name="5a_right_hand" pos=".18 .18 .18">
            <geom name="5a_right_hand" type="sphere" size=".04" zaxis="1 1 1"/>
          </body>
        </body>
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      <body name="5a_left_upper_arm" pos="0 .17 .06">
        <joint name="5a_left_shoulder1" axis="2 -1 1" range="-60 85"/>
        <joint name="5a_left_shoulder2" axis="0 1 1"  range="-60 85"/>
        <geom name="5a_left_upper_arm" fromto="0 0 0 .16 .16 -.16" size=".04 .16"/>
        <body name="5a_left_lower_arm" pos=".18 .18 -.18">
          <joint name="5a_left_elbow" axis="0 -1 -1" range="-90 50" stiffness="0"/>
          <geom name="5a_left_lower_arm" fromto=".01 -.01 .01 .17 -.17 .17" size=".031"/>
          <body name="5a_left_hand" pos=".18 -.18 .18">
            <geom name="5a_left_hand" type="sphere" size=".04" zaxis="1 -1 1"/>
          </body>
        </body>
      </body>
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      <camera name="6a_back" pos="-3 0 1" xyaxes="0 -1 0 1 0 2" mode="trackcom"/>
      <camera name="6a_side" pos="0 -3 1" xyaxes="1 0 0 0 1 2" mode="trackcom"/>
      <freejoint name="6a_root"/>
      <geom name="6a_torso" fromto="0 -.07 0 0 .07 0" size=".07"/>
      <geom name="6a_upper_waist" fromto="-.01 -.06 -.12 -.01 .06 -.12" size=".06"/>
      <body name="6a_head" pos="0 0 .19">
        <geom name="6a_head" type="sphere" size=".09"/>
        <camera name="6a_egocentric" pos=".09 0 0" xyaxes="0 -1 0 .1 0 1" fovy="80"/>
      </body>
      <body name="6a_lower_waist" pos="-.01 0 -.26">
        <geom name="6a_lower_waist" fromto="0 -.06 0 0 .06 0" size=".06"/>
        <joint name="6a_abdomen_z" pos="0 0 .065" axis="0 0 1" range="-45 45" class="big_stiff_joint"/>
        <joint name="6a_abdomen_y" pos="0 0 .065" axis="0 1 0" range="-75 30" class="big_joint"/>
        <body name="6a_pelvis" pos="0 0 -.165">
          <joint name="6a_abdomen_x" pos="0 0 .1" axis="1 0 0" range="-35 35" class="big_joint"/>
          <geom name="6a_butt" fromto="-.02 -.07 0 -.02 .07 0" size=".09"/>
          <body name="6a_right_thigh" pos="0 -.1 -.04">
            <joint name="6a_right_hip_x" axis="1 0 0" range="-25 5" class="big_joint"/>
            <joint name="6a_right_hip_z" axis="0 0 1" range="-60 35" class="big_joint"/>
            <joint name="6a_right_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="6a_right_thigh" fromto="0 0 0 0 .01 -.34" size=".06"/>
            <body name="6a_right_shin" pos="0 .01 -.403">
              <joint name="6a_right_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="6a_right_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="6a_right_foot" pos="0 0 -.39">
                <joint name="6a_right_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="6a_right_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="6a_right_right_foot" fromto="-.07 -.02 0 .14 -.04 0" size=".027"/>
                <geom name="6a_left_right_foot" fromto="-.07 0 0 .14  .02 0" size=".027"/>
              </body>
            </body>
          </body>
          <body name="6a_left_thigh" pos="0 .1 -.04">
            <joint name="6a_left_hip_x" axis="-1 0 0" range="-25 5" class="big_joint"/>
            <joint name="6a_left_hip_z" axis="0 0 -1" range="-60 35" class="big_joint"/>
            <joint name="6a_left_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="6a_left_thigh" fromto="0 0 0 0 -.01 -.34" size=".06"/>
            <body name="6a_left_shin" pos="0 -.01 -.403">
              <joint name="6a_left_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="6a_left_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="6a_left_foot" pos="0 0 -.39">
                <joint name="6a_left_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="6a_left_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="6a_left_left_foot" fromto="-.07 .02 0 .14 .04 0" size=".027"/>
                <geom name="6a_right_left_foot" fromto="-.07 0 0 .14 -.02 0" size=".027"/>
              </body>
            </body>
          </body>
        </body>
      </body>
      <body name="6a_right_upper_arm" pos="0 -.17 .06">
        <joint name="6a_right_shoulder1" axis="2 1 1"  range="-85 60"/>
        <joint name="6a_right_shoulder2" axis="0 -1 1" range="-85 60"/>
        <geom name="6a_right_upper_arm" fromto="0 0 0 .16 -.16 -.16" size=".04 .16"/>
        <body name="6a_right_lower_arm" pos=".18 -.18 -.18">
          <joint name="6a_right_elbow" axis="0 -1 1" range="-90 50" stiffness="0"/>
          <geom name="6a_right_lower_arm" fromto=".01 .01 .01 .17 .17 .17" size=".031"/>
          <body name="6a_right_hand" pos=".18 .18 .18">
            <geom name="6a_right_hand" type="sphere" size=".04" zaxis="1 1 1"/>
          </body>
        </body>
      </body>
      <body name="6a_left_upper_arm" pos="0 .17 .06">
        <joint name="6a_left_shoulder1" axis="2 -1 1" range="-60 85"/>
        <joint name="6a_left_shoulder2" axis="0 1 1"  range="-60 85"/>
        <geom name="6a_left_upper_arm" fromto="0 0 0 .16 .16 -.16" size=".04 .16"/>
        <body name="6a_left_lower_arm" pos=".18 .18 -.18">
          <joint name="6a_left_elbow" axis="0 -1 -1" range="-90 50" stiffness="0"/>
          <geom name="6a_left_lower_arm" fromto=".01 -.01 .01 .17 -.17 .17" size=".031"/>
          <body name="6a_left_hand" pos=".18 -.18 .18">
            <geom name="6a_left_hand" type="sphere" size=".04" zaxis="1 -1 1"/>
          </body>
        </body>
      </body>
    </body>
    <body name="7a_torso" pos="-1 -3 1.5" childclass="body7">
      <camera name="7a_back" pos="-3 0 1" xyaxes="0 -1 0 1 0 2" mode="trackcom"/>
      <camera name="7a_side" pos="0 -3 1" xyaxes="1 0 0 0 1 2" mode="trackcom"/>
      <freejoint name="7a_root"/>
      <geom name="7a_torso" fromto="0 -.07 0 0 .07 0" size=".07"/>
      <geom name="7a_upper_waist" fromto="-.01 -.06 -.12 -.01 .06 -.12" size=".06"/>
      <body name="7a_head" pos="0 0 .19">
        <geom name="7a_head" type="sphere" size=".09"/>
        <camera name="7a_egocentric" pos=".09 0 0" xyaxes="0 -1 0 .1 0 1" fovy="80"/>
      </body>
      <body name="7a_lower_waist" pos="-.01 0 -.26">
        <geom name="7a_lower_waist" fromto="0 -.06 0 0 .06 0" size=".06"/>
        <joint name="7a_abdomen_z" pos="0 0 .065" axis="0 0 1" range="-45 45" class="big_stiff_joint"/>
        <joint name="7a_abdomen_y" pos="0 0 .065" axis="0 1 0" range="-75 30" class="big_joint"/>
        <body name="7a_pelvis" pos="0 0 -.165">
          <joint name="7a_abdomen_x" pos="0 0 .1" axis="1 0 0" range="-35 35" class="big_joint"/>
          <geom name="7a_butt" fromto="-.02 -.07 0 -.02 .07 0" size=".09"/>
          <body name="7a_right_thigh" pos="0 -.1 -.04">
            <joint name="7a_right_hip_x" axis="1 0 0" range="-25 5" class="big_joint"/>
            <joint name="7a_right_hip_z" axis="0 0 1" range="-60 35" class="big_joint"/>
            <joint name="7a_right_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="7a_right_thigh" fromto="0 0 0 0 .01 -.34" size=".06"/>
            <body name="7a_right_shin" pos="0 .01 -.403">
              <joint name="7a_right_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="7a_right_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="7a_right_foot" pos="0 0 -.39">
                <joint name="7a_right_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="7a_right_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="7a_right_right_foot" fromto="-.07 -.02 0 .14 -.04 0" size=".027"/>
                <geom name="7a_left_right_foot" fromto="-.07 0 0 .14  .02 0" size=".027"/>
              </body>
            </body>
          </body>
          <body name="7a_left_thigh" pos="0 .1 -.04">
            <joint name="7a_left_hip_x" axis="-1 0 0" range="-25 5" class="big_joint"/>
            <joint name="7a_left_hip_z" axis="0 0 -1" range="-60 35" class="big_joint"/>
            <joint name="7a_left_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="7a_left_thigh" fromto="0 0 0 0 -.01 -.34" size=".06"/>
            <body name="7a_left_shin" pos="0 -.01 -.403">
              <joint name="7a_left_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="7a_left_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="7a_left_foot" pos="0 0 -.39">
                <joint name="7a_left_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="7a_left_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="7a_left_left_foot" fromto="-.07 .02 0 .14 .04 0" size=".027"/>
                <geom name="7a_right_left_foot" fromto="-.07 0 0 .14 -.02 0" size=".027"/>
              </body>
            </body>
          </body>
        </body>
      </body>
      <body name="7a_right_upper_arm" pos="0 -.17 .06">
        <joint name="7a_right_shoulder1" axis="2 1 1"  range="-85 60"/>
        <joint name="7a_right_shoulder2" axis="0 -1 1" range="-85 60"/>
        <geom name="7a_right_upper_arm" fromto="0 0 0 .16 -.16 -.16" size=".04 .16"/>
        <body name="7a_right_lower_arm" pos=".18 -.18 -.18">
          <joint name="7a_right_elbow" axis="0 -1 1" range="-90 50" stiffness="0"/>
          <geom name="7a_right_lower_arm" fromto=".01 .01 .01 .17 .17 .17" size=".031"/>
          <body name="7a_right_hand" pos=".18 .18 .18">
            <geom name="7a_right_hand" type="sphere" size=".04" zaxis="1 1 1"/>
          </body>
        </body>
      </body>
      <body name="7a_left_upper_arm" pos="0 .17 .06">
        <joint name="7a_left_shoulder1" axis="2 -1 1" range="-60 85"/>
        <joint name="7a_left_shoulder2" axis="0 1 1"  range="-60 85"/>
        <geom name="7a_left_upper_arm" fromto="0 0 0 .16 .16 -.16" size=".04 .16"/>
        <body name="7a_left_lower_arm" pos=".18 .18 -.18">
          <joint name="7a_left_elbow" axis="0 -1 -1" range="-90 50" stiffness="0"/>
          <geom name="7a_left_lower_arm" fromto=".01 -.01 .01 .17 -.17 .17" size=".031"/>
          <body name="7a_left_hand" pos=".18 -.18 .18">
            <geom name="7a_left_hand" type="sphere" size=".04" zaxis="1 -1 1"/>
          </body>
        </body>
      </body>
    </body>
    <body name="8a_torso" pos="-1 4 1.5" childclass="body8">
      <camera name="8a_back" pos="-3 0 1" xyaxes="0 -1 0 1 0 2" mode="trackcom"/>
      <camera name="8a_side" pos="0 -3 1" xyaxes="1 0 0 0 1 2" mode="trackcom"/>
      <freejoint name="8a_root"/>
      <geom name="8a_torso" fromto="0 -.07 0 0 .07 0" size=".07"/>
      <geom name="8a_upper_waist" fromto="-.01 -.06 -.12 -.01 .06 -.12" size=".06"/>
      <body name="8a_head" pos="0 0 .19">
        <geom name="8a_head" type="sphere" size=".09"/>
        <camera name="8a_egocentric" pos=".09 0 0" xyaxes="0 -1 0 .1 0 1" fovy="80"/>
      </body>
      <body name="8a_lower_waist" pos="-.01 0 -.26">
        <geom name="8a_lower_waist" fromto="0 -.06 0 0 .06 0" size=".06"/>
        <joint name="8a_abdomen_z" pos="0 0 .065" axis="0 0 1" range="-45 45" class="big_stiff_joint"/>
        <joint name="8a_abdomen_y" pos="0 0 .065" axis="0 1 0" range="-75 30" class="big_joint"/>
        <body name="8a_pelvis" pos="0 0 -.165">
          <joint name="8a_abdomen_x" pos="0 0 .1" axis="1 0 0" range="-35 35" class="big_joint"/>
          <geom name="8a_butt" fromto="-.02 -.07 0 -.02 .07 0" size=".09"/>
          <body name="8a_right_thigh" pos="0 -.1 -.04">
            <joint name="8a_right_hip_x" axis="1 0 0" range="-25 5" class="big_joint"/>
            <joint name="8a_right_hip_z" axis="0 0 1" range="-60 35" class="big_joint"/>
            <joint name="8a_right_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="8a_right_thigh" fromto="0 0 0 0 .01 -.34" size=".06"/>
            <body name="8a_right_shin" pos="0 .01 -.403">
              <joint name="8a_right_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="8a_right_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="8a_right_foot" pos="0 0 -.39">
                <joint name="8a_right_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="8a_right_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="8a_right_right_foot" fromto="-.07 -.02 0 .14 -.04 0" size=".027"/>
                <geom name="8a_left_right_foot" fromto="-.07 0 0 .14  .02 0" size=".027"/>
              </body>
            </body>
          </body>
          <body name="8a_left_thigh" pos="0 .1 -.04">
            <joint name="8a_left_hip_x" axis="-1 0 0" range="-25 5" class="big_joint"/>
            <joint name="8a_left_hip_z" axis="0 0 -1" range="-60 35" class="big_joint"/>
            <joint name="8a_left_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="8a_left_thigh" fromto="0 0 0 0 -.01 -.34" size=".06"/>
            <body name="8a_left_shin" pos="0 -.01 -.403">
              <joint name="8a_left_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="8a_left_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="8a_left_foot" pos="0 0 -.39">
                <joint name="8a_left_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="8a_left_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="8a_left_left_foot" fromto="-.07 .02 0 .14 .04 0" size=".027"/>
                <geom name="8a_right_left_foot" fromto="-.07 0 0 .14 -.02 0" size=".027"/>
              </body>
            </body>
          </body>
        </body>
      </body>
      <body name="8a_right_upper_arm" pos="0 -.17 .06">
        <joint name="8a_right_shoulder1" axis="2 1 1"  range="-85 60"/>
        <joint name="8a_right_shoulder2" axis="0 -1 1" range="-85 60"/>
        <geom name="8a_right_upper_arm" fromto="0 0 0 .16 -.16 -.16" size=".04 .16"/>
        <body name="8a_right_lower_arm" pos=".18 -.18 -.18">
          <joint name="8a_right_elbow" axis="0 -1 1" range="-90 50" stiffness="0"/>
          <geom name="8a_right_lower_arm" fromto=".01 .01 .01 .17 .17 .17" size=".031"/>
          <body name="8a_right_hand" pos=".18 .18 .18">
            <geom name="8a_right_hand" type="sphere" size=".04" zaxis="1 1 1"/>
          </body>
        </body>
      </body>
      <body name="8a_left_upper_arm" pos="0 .17 .06">
        <joint name="8a_left_shoulder1" axis="2 -1 1" range="-60 85"/>
        <joint name="8a_left_shoulder2" axis="0 1 1"  range="-60 85"/>
        <geom name="8a_left_upper_arm" fromto="0 0 0 .16 .16 -.16" size=".04 .16"/>
        <body name="8a_left_lower_arm" pos=".18 .18 -.18">
          <joint name="8a_left_elbow" axis="0 -1 -1" range="-90 50" stiffness="0"/>
          <geom name="8a_left_lower_arm" fromto=".01 -.01 .01 .17 -.17 .17" size=".031"/>
          <body name="8a_left_hand" pos=".18 -.18 .18">
            <geom name="8a_left_hand" type="sphere" size=".04" zaxis="1 -1 1"/>
          </body>
        </body>
      </body>
    </body>
  </worldbody>
  <actuator>
    <motor gear="40"  joint="1a_abdomen_y"/>
    <motor gear="40"  joint="1a_abdomen_z"/>
    <motor gear="40"  joint="1a_abdomen_x"/>
    <motor gear="40"  joint="1a_right_hip_x"/>
    <motor gear="40"  joint="1a_right_hip_z"/>
    <motor gear="120" joint="1a_right_hip_y"/>
    <motor gear="80"  joint="1a_right_knee"/>
    <motor gear="20"  joint="1a_right_ankle_x"/>
    <motor gear="20"  joint="1a_right_ankle_y"/>
    <motor gear="40"  joint="1a_left_hip_x"/>
    <motor gear="40"  joint="1a_left_hip_z"/>
    <motor gear="120" joint="1a_left_hip_y"/>
    <motor gear="80"  joint="1a_left_knee"/>
    <motor gear="20"  joint="1a_left_ankle_x"/>
    <motor gear="20"  joint="1a_left_ankle_y"/>
    <motor gear="20"  joint="1a_right_shoulder1"/>
    <motor gear="20"  joint="1a_right_shoulder2"/>
    <motor gear="40"  joint="1a_right_elbow"/>
    <motor gear="20"  joint="1a_left_shoulder1"/>
    <motor gear="20"  joint="1a_left_shoulder2"/>
    <motor gear="40"  joint="1a_left_elbow"/>
  </actuator>
  <actuator>
    <motor gear="40"  joint="2a_abdomen_y"/>
    <motor gear="40"  joint="2a_abdomen_z"/>
    <motor gear="40"  joint="2a_abdomen_x"/>
    <motor gear="40"  joint="2a_right_hip_x"/>
    <motor gear="40"  joint="2a_right_hip_z"/>
    <motor gear="120" joint="2a_right_hip_y"/>
    <motor gear="80"  joint="2a_right_knee"/>
    <motor gear="20"  joint="2a_right_ankle_x"/>
    <motor gear="20"  joint="2a_right_ankle_y"/>
    <motor gear="40"  joint="2a_left_hip_x"/>
    <motor gear="40"  joint="2a_left_hip_z"/>
    <motor gear="120" joint="2a_left_hip_y"/>
    <motor gear="80"  joint="2a_left_knee"/>
    <motor gear="20"  joint="2a_left_ankle_x"/>
    <motor gear="20"  joint="2a_left_ankle_y"/>
    <motor gear="20"  joint="2a_right_shoulder1"/>
    <motor gear="20"  joint="2a_right_shoulder2"/>
    <motor gear="40"  joint="2a_right_elbow"/>
    <motor gear="20"  joint="2a_left_shoulder1"/>
    <motor gear="20"  joint="2a_left_shoulder2"/>
    <motor gear="40"  joint="2a_left_elbow"/>
  </actuator>
  <actuator>
    <motor gear="40"  joint="3a_abdomen_y"/>
    <motor gear="40"  joint="3a_abdomen_z"/>
    <motor gear="40"  joint="3a_abdomen_x"/>
    <motor gear="40"  joint="3a_right_hip_x"/>
    <motor gear="40"  joint="3a_right_hip_z"/>
    <motor gear="120" joint="3a_right_hip_y"/>
    <motor gear="80"  joint="3a_right_knee"/>
    <motor gear="20"  joint="3a_right_ankle_x"/>
    <motor gear="20"  joint="3a_right_ankle_y"/>
    <motor gear="40"  joint="3a_left_hip_x"/>
    <motor gear="40"  joint="3a_left_hip_z"/>
    <motor gear="120" joint="3a_left_hip_y"/>
    <motor gear="80"  joint="3a_left_knee"/>
    <motor gear="20"  joint="3a_left_ankle_x"/>
    <motor gear="20"  joint="3a_left_ankle_y"/>
    <motor gear="20"  joint="3a_right_shoulder1"/>
    <motor gear="20"  joint="3a_right_shoulder2"/>
    <motor gear="40"  joint="3a_right_elbow"/>
    <motor gear="20"  joint="3a_left_shoulder1"/>
    <motor gear="20"  joint="3a_left_shoulder2"/>
    <motor gear="40"  joint="3a_left_elbow"/>
  </actuator>
  <actuator>
    <motor gear="40"  joint="4a_abdomen_y"/>
    <motor gear="40"  joint="4a_abdomen_z"/>
    <motor gear="40"  joint="4a_abdomen_x"/>
    <motor gear="40"  joint="4a_right_hip_x"/>
    <motor gear="40"  joint="4a_right_hip_z"/>
    <motor gear="120" joint="4a_right_hip_y"/>
    <motor gear="80"  joint="4a_right_knee"/>
    <motor gear="20"  joint="4a_right_ankle_x"/>
    <motor gear="20"  joint="4a_right_ankle_y"/>
    <motor gear="40"  joint="4a_left_hip_x"/>
    <motor gear="40"  joint="4a_left_hip_z"/>
    <motor gear="120" joint="4a_left_hip_y"/>
    <motor gear="80"  joint="4a_left_knee"/>
    <motor gear="20"  joint="4a_left_ankle_x"/>
    <motor gear="20"  joint="4a_left_ankle_y"/>
    <motor gear="20"  joint="4a_right_shoulder1"/>
    <motor gear="20"  joint="4a_right_shoulder2"/>
    <motor gear="40"  joint="4a_right_elbow"/>
    <motor gear="20"  joint="4a_left_shoulder1"/>
    <motor gear="20"  joint="4a_left_shoulder2"/>
    <motor gear="40"  joint="4a_left_elbow"/>
  </actuator>
  <actuator>
    <motor gear="40"  joint="5a_abdomen_y"/>
    <motor gear="40"  joint="5a_abdomen_z"/>
    <motor gear="40"  joint="5a_abdomen_x"/>
    <motor gear="40"  joint="5a_right_hip_x"/>
    <motor gear="40"  joint="5a_right_hip_z"/>
    <motor gear="120" joint="5a_right_hip_y"/>
    <motor gear="80"  joint="5a_right_knee"/>
    <motor gear="20"  joint="5a_right_ankle_x"/>
    <motor gear="20"  joint="5a_right_ankle_y"/>
    <motor gear="40"  joint="5a_left_hip_x"/>
    <motor gear="40"  joint="5a_left_hip_z"/>
    <motor gear="120" joint="5a_left_hip_y"/>
    <motor gear="80"  joint="5a_left_knee"/>
    <motor gear="20"  joint="5a_left_ankle_x"/>
    <motor gear="20"  joint="5a_left_ankle_y"/>
    <motor gear="20"  joint="5a_right_shoulder1"/>
    <motor gear="20"  joint="5a_right_shoulder2"/>
    <motor gear="40"  joint="5a_right_elbow"/>
    <motor gear="20"  joint="5a_left_shoulder1"/>
    <motor gear="20"  joint="5a_left_shoulder2"/>
    <motor gear="40"  joint="5a_left_elbow"/>
  </actuator>
  <actuator>
    <motor gear="40"  joint="6a_abdomen_y"/>
    <motor gear="40"  joint="6a_abdomen_z"/>
    <motor gear="40"  joint="6a_abdomen_x"/>
    <motor gear="40"  joint="6a_right_hip_x"/>
    <motor gear="40"  joint="6a_right_hip_z"/>
    <motor gear="120" joint="6a_right_hip_y"/>
    <motor gear="80"  joint="6a_right_knee"/>
    <motor gear="20"  joint="6a_right_ankle_x"/>
    <motor gear="20"  joint="6a_right_ankle_y"/>
    <motor gear="40"  joint="6a_left_hip_x"/>
    <motor gear="40"  joint="6a_left_hip_z"/>
    <motor gear="120" joint="6a_left_hip_y"/>
    <motor gear="80"  joint="6a_left_knee"/>
    <motor gear="20"  joint="6a_left_ankle_x"/>
    <motor gear="20"  joint="6a_left_ankle_y"/>
    <motor gear="20"  joint="6a_right_shoulder1"/>
    <motor gear="20"  joint="6a_right_shoulder2"/>
    <motor gear="40"  joint="6a_right_elbow"/>
    <motor gear="20"  joint="6a_left_shoulder1"/>
    <motor gear="20"  joint="6a_left_shoulder2"/>
    <motor gear="40"  joint="6a_left_elbow"/>
  </actuator>
  <actuator>
    <motor gear="40"  joint="7a_abdomen_y"/>
    <motor gear="40"  joint="7a_abdomen_z"/>
    <motor gear="40"  joint="7a_abdomen_x"/>
    <motor gear="40"  joint="7a_right_hip_x"/>
    <motor gear="40"  joint="7a_right_hip_z"/>
    <motor gear="120" joint="7a_right_hip_y"/>
    <motor gear="80"  joint="7a_right_knee"/>
    <motor gear="20"  joint="7a_right_ankle_x"/>
    <motor gear="20"  joint="7a_right_ankle_y"/>
    <motor gear="40"  joint="7a_left_hip_x"/>
    <motor gear="40"  joint="7a_left_hip_z"/>
    <motor gear="120" joint="7a_left_hip_y"/>
    <motor gear="80"  joint="7a_left_knee"/>
    <motor gear="20"  joint="7a_left_ankle_x"/>
    <motor gear="20"  joint="7a_left_ankle_y"/>
    <motor gear="20"  joint="7a_right_shoulder1"/>
    <motor gear="20"  joint="7a_right_shoulder2"/>
    <motor gear="40"  joint="7a_right_elbow"/>
    <motor gear="20"  joint="7a_left_shoulder1"/>
    <motor gear="20"  joint="7a_left_shoulder2"/>
    <motor gear="40"  joint="7a_left_elbow"/>
  </actuator>
  <actuator>
    <motor gear="40"  joint="8a_abdomen_y"/>
    <motor gear="40"  joint="8a_abdomen_z"/>
    <motor gear="40"  joint="8a_abdomen_x"/>
    <motor gear="40"  joint="8a_right_hip_x"/>
    <motor gear="40"  joint="8a_right_hip_z"/>
    <motor gear="120" joint="8a_right_hip_y"/>
    <motor gear="80"  joint="8a_right_knee"/>
    <motor gear="20"  joint="8a_right_ankle_x"/>
    <motor gear="20"  joint="8a_right_ankle_y"/>
    <motor gear="40"  joint="8a_left_hip_x"/>
    <motor gear="40"  joint="8a_left_hip_z"/>
    <motor gear="120" joint="8a_left_hip_y"/>
    <motor gear="80"  joint="8a_left_knee"/>
    <motor gear="20"  joint="8a_left_ankle_x"/>
    <motor gear="20"  joint="8a_left_ankle_y"/>
    <motor gear="20"  joint="8a_right_shoulder1"/>
    <motor gear="20"  joint="8a_right_shoulder2"/>
    <motor gear="40"  joint="8a_right_elbow"/>
    <motor gear="20"  joint="8a_left_shoulder1"/>
    <motor gear="20"  joint="8a_left_shoulder2"/>
    <motor gear="40"  joint="8a_left_elbow"/>
  </actuator>
 </mujoco>
@@ -0,0 +1,983 @@
 <mujoco model="09 Humanoids">
  <option timestep="0.005" solver="Newton" iterations="1" ls_iterations="4">
    <flag eulerdamp="disable"/>
  </option>
  <custom>
    <numeric data="36" name="max_contact_points"/>
    <numeric data="36" name="max_geom_pairs"/>
  </custom>
  <size memory="100M"/>
  <asset>
    <texture type="skybox" builtin="gradient" rgb1=".3 .5 .7" rgb2="0 0 0" width="512" height="512"/>
    <texture name="body" type="cube" builtin="flat" mark="cross" width="128" height="128"
             rgb1="0.8 0.6 0.4" rgb2="0.8 0.6 0.4" markrgb="1 1 1" random="0.01"/>
    <material name="body" texture="body" texuniform="true" rgba="0.8 0.6 .4 1"/>
    <texture name="grid" type="2d" builtin="checker" width="512" height="512" rgb1=".1 .2 .3" rgb2=".2 .3 .4"/>
    <material name="grid" texture="grid" texrepeat="1 1" texuniform="true" reflectance=".2"/>
  </asset>
  <default>
    <motor ctrlrange="-1 1" ctrllimited="true"/>
    <joint type="hinge" damping=".2" stiffness="1" armature=".01" limited="true" solimplimit="0 .99 .01"/>
    <default class="big_joint">
      <joint damping="5" stiffness="10"/>
      <default class="big_stiff_joint">
        <joint stiffness="20"/>
      </default>
    </default>
    <default class="body1">
      <geom type="capsule" condim="3" friction=".7" solimp=".9 .99 .003" solref=".015 1" material="body" contype="2" conaffinity="1021"/>
    </default>
    <default class="body2">
      <geom type="capsule" condim="3" friction=".7" solimp=".9 .99 .003" solref=".015 1" material="body" contype="4" conaffinity="1019"/>
    </default>
    <default class="body3">
      <geom type="capsule" condim="3" friction=".7" solimp=".9 .99 .003" solref=".015 1" material="body" contype="8" conaffinity="1015"/>
    </default>
    <default class="body4">
      <geom type="capsule" condim="3" friction=".7" solimp=".9 .99 .003" solref=".015 1" material="body" contype="16" conaffinity="1007"/>
    </default>
    <default class="body5">
      <geom type="capsule" condim="3" friction=".7" solimp=".9 .99 .003" solref=".015 1" material="body" contype="32" conaffinity="991"/>
    </default>
    <default class="body6">
      <geom type="capsule" condim="3" friction=".7" solimp=".9 .99 .003" solref=".015 1" material="body" contype="64" conaffinity="959"/>
    </default>
    <default class="body7">
      <geom type="capsule" condim="3" friction=".7" solimp=".9 .99 .003" solref=".015 1" material="body" contype="128" conaffinity="895"/>
    </default>
    <default class="body8">
      <geom type="capsule" condim="3" friction=".7" solimp=".9 .99 .003" solref=".015 1" material="body" contype="256" conaffinity="767"/>
    </default>
    <default class="body9">
      <geom type="capsule" condim="3" friction=".7" solimp=".9 .99 .003" solref=".015 1" material="body" contype="512" conaffinity="511"/>
    </default>
  </default>
  <visual>
    <map force="0.1" zfar="30"/>
    <rgba haze="0.15 0.25 0.35 1"/>
    <quality shadowsize="4096"/>
    <global offwidth="800" offheight="800"/>
  </visual>
  <worldbody>
    <geom size="10 10 .05" type="plane" material="grid" condim="3"/>
    <light dir=".2 1 -.4" diffuse=".8 .8 .8" specular="0.3 0.3 0.3" pos="-2 -10 4" cutoff="35"/>
    <light dir="-.2 1 -.4" diffuse=".8 .8 .8" specular="0.3 0.3 0.3" pos="2 -10 4" cutoff="35"/>
    <body name="1a_torso" pos="-1 0 1.5" childclass="body1">
      <camera name="1a_back" pos="-3 0 1" xyaxes="0 -1 0 1 0 2" mode="trackcom"/>
      <camera name="1a_side" pos="0 -3 1" xyaxes="1 0 0 0 1 2" mode="trackcom"/>
      <freejoint name="1a_root"/>
      <geom name="1a_torso" fromto="0 -.07 0 0 .07 0" size=".07"/>
      <geom name="1a_upper_waist" fromto="-.01 -.06 -.12 -.01 .06 -.12" size=".06"/>
      <body name="1a_head" pos="0 0 .19">
        <geom name="1a_head" type="sphere" size=".09"/>
        <camera name="1a_egocentric" pos=".09 0 0" xyaxes="0 -1 0 .1 0 1" fovy="80"/>
      </body>
      <body name="1a_lower_waist" pos="-.01 0 -.26">
        <geom name="1a_lower_waist" fromto="0 -.06 0 0 .06 0" size=".06"/>
        <joint name="1a_abdomen_z" pos="0 0 .065" axis="0 0 1" range="-45 45" class="big_stiff_joint"/>
        <joint name="1a_abdomen_y" pos="0 0 .065" axis="0 1 0" range="-75 30" class="big_joint"/>
        <body name="1a_pelvis" pos="0 0 -.165">
          <joint name="1a_abdomen_x" pos="0 0 .1" axis="1 0 0" range="-35 35" class="big_joint"/>
          <geom name="1a_butt" fromto="-.02 -.07 0 -.02 .07 0" size=".09"/>
          <body name="1a_right_thigh" pos="0 -.1 -.04">
            <joint name="1a_right_hip_x" axis="1 0 0" range="-25 5" class="big_joint"/>
            <joint name="1a_right_hip_z" axis="0 0 1" range="-60 35" class="big_joint"/>
            <joint name="1a_right_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="1a_right_thigh" fromto="0 0 0 0 .01 -.34" size=".06"/>
            <body name="1a_right_shin" pos="0 .01 -.403">
              <joint name="1a_right_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="1a_right_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="1a_right_foot" pos="0 0 -.39">
                <joint name="1a_right_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="1a_right_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="1a_right_right_foot" fromto="-.07 -.02 0 .14 -.04 0" size=".027"/>
                <geom name="1a_left_right_foot" fromto="-.07 0 0 .14  .02 0" size=".027"/>
              </body>
            </body>
          </body>
          <body name="1a_left_thigh" pos="0 .1 -.04">
            <joint name="1a_left_hip_x" axis="-1 0 0" range="-25 5" class="big_joint"/>
            <joint name="1a_left_hip_z" axis="0 0 -1" range="-60 35" class="big_joint"/>
            <joint name="1a_left_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="1a_left_thigh" fromto="0 0 0 0 -.01 -.34" size=".06"/>
            <body name="1a_left_shin" pos="0 -.01 -.403">
              <joint name="1a_left_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="1a_left_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="1a_left_foot" pos="0 0 -.39">
                <joint name="1a_left_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="1a_left_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="1a_left_left_foot" fromto="-.07 .02 0 .14 .04 0" size=".027"/>
                <geom name="1a_right_left_foot" fromto="-.07 0 0 .14 -.02 0" size=".027"/>
              </body>
            </body>
          </body>
        </body>
      </body>
      <body name="1a_right_upper_arm" pos="0 -.17 .06">
        <joint name="1a_right_shoulder1" axis="2 1 1"  range="-85 60"/>
        <joint name="1a_right_shoulder2" axis="0 -1 1" range="-85 60"/>
        <geom name="1a_right_upper_arm" fromto="0 0 0 .16 -.16 -.16" size=".04 .16"/>
        <body name="1a_right_lower_arm" pos=".18 -.18 -.18">
          <joint name="1a_right_elbow" axis="0 -1 1" range="-90 50" stiffness="0"/>
          <geom name="1a_right_lower_arm" fromto=".01 .01 .01 .17 .17 .17" size=".031"/>
          <body name="1a_right_hand" pos=".18 .18 .18">
            <geom name="1a_right_hand" type="sphere" size=".04" zaxis="1 1 1"/>
          </body>
        </body>
      </body>
      <body name="1a_left_upper_arm" pos="0 .17 .06">
        <joint name="1a_left_shoulder1" axis="2 -1 1" range="-60 85"/>
        <joint name="1a_left_shoulder2" axis="0 1 1"  range="-60 85"/>
        <geom name="1a_left_upper_arm" fromto="0 0 0 .16 .16 -.16" size=".04 .16"/>
        <body name="1a_left_lower_arm" pos=".18 .18 -.18">
          <joint name="1a_left_elbow" axis="0 -1 -1" range="-90 50" stiffness="0"/>
          <geom name="1a_left_lower_arm" fromto=".01 -.01 .01 .17 -.17 .17" size=".031"/>
          <body name="1a_left_hand" pos=".18 -.18 .18">
            <geom name="1a_left_hand" type="sphere" size=".04" zaxis="1 -1 1"/>
          </body>
        </body>
      </body>
    </body>
    <body name="2a_torso" pos="-1 1 1.5" childclass="body2">
      <camera name="2a_back" pos="-3 0 1" xyaxes="0 -1 0 1 0 2" mode="trackcom"/>
      <camera name="2a_side" pos="0 -3 1" xyaxes="1 0 0 0 1 2" mode="trackcom"/>
      <freejoint name="2a_root"/>
      <geom name="2a_torso" fromto="0 -.07 0 0 .07 0" size=".07"/>
      <geom name="2a_upper_waist" fromto="-.01 -.06 -.12 -.01 .06 -.12" size=".06"/>
      <body name="2a_head" pos="0 0 .19">
        <geom name="2a_head" type="sphere" size=".09"/>
        <camera name="2a_egocentric" pos=".09 0 0" xyaxes="0 -1 0 .1 0 1" fovy="80"/>
      </body>
      <body name="2a_lower_waist" pos="-.01 0 -.26">
        <geom name="2a_lower_waist" fromto="0 -.06 0 0 .06 0" size=".06"/>
        <joint name="2a_abdomen_z" pos="0 0 .065" axis="0 0 1" range="-45 45" class="big_stiff_joint"/>
        <joint name="2a_abdomen_y" pos="0 0 .065" axis="0 1 0" range="-75 30" class="big_joint"/>
        <body name="2a_pelvis" pos="0 0 -.165">
          <joint name="2a_abdomen_x" pos="0 0 .1" axis="1 0 0" range="-35 35" class="big_joint"/>
          <geom name="2a_butt" fromto="-.02 -.07 0 -.02 .07 0" size=".09"/>
          <body name="2a_right_thigh" pos="0 -.1 -.04">
            <joint name="2a_right_hip_x" axis="1 0 0" range="-25 5" class="big_joint"/>
            <joint name="2a_right_hip_z" axis="0 0 1" range="-60 35" class="big_joint"/>
            <joint name="2a_right_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="2a_right_thigh" fromto="0 0 0 0 .01 -.34" size=".06"/>
            <body name="2a_right_shin" pos="0 .01 -.403">
              <joint name="2a_right_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="2a_right_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="2a_right_foot" pos="0 0 -.39">
                <joint name="2a_right_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="2a_right_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="2a_right_right_foot" fromto="-.07 -.02 0 .14 -.04 0" size=".027"/>
                <geom name="2a_left_right_foot" fromto="-.07 0 0 .14  .02 0" size=".027"/>
              </body>
            </body>
          </body>
          <body name="2a_left_thigh" pos="0 .1 -.04">
            <joint name="2a_left_hip_x" axis="-1 0 0" range="-25 5" class="big_joint"/>
            <joint name="2a_left_hip_z" axis="0 0 -1" range="-60 35" class="big_joint"/>
            <joint name="2a_left_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="2a_left_thigh" fromto="0 0 0 0 -.01 -.34" size=".06"/>
            <body name="2a_left_shin" pos="0 -.01 -.403">
              <joint name="2a_left_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="2a_left_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="2a_left_foot" pos="0 0 -.39">
                <joint name="2a_left_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="2a_left_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="2a_left_left_foot" fromto="-.07 .02 0 .14 .04 0" size=".027"/>
                <geom name="2a_right_left_foot" fromto="-.07 0 0 .14 -.02 0" size=".027"/>
              </body>
            </body>
          </body>
        </body>
      </body>
      <body name="2a_right_upper_arm" pos="0 -.17 .06">
        <joint name="2a_right_shoulder1" axis="2 1 1"  range="-85 60"/>
        <joint name="2a_right_shoulder2" axis="0 -1 1" range="-85 60"/>
        <geom name="2a_right_upper_arm" fromto="0 0 0 .16 -.16 -.16" size=".04 .16"/>
        <body name="2a_right_lower_arm" pos=".18 -.18 -.18">
          <joint name="2a_right_elbow" axis="0 -1 1" range="-90 50" stiffness="0"/>
          <geom name="2a_right_lower_arm" fromto=".01 .01 .01 .17 .17 .17" size=".031"/>
          <body name="2a_right_hand" pos=".18 .18 .18">
            <geom name="2a_right_hand" type="sphere" size=".04" zaxis="1 1 1"/>
          </body>
        </body>
      </body>
      <body name="2a_left_upper_arm" pos="0 .17 .06">
        <joint name="2a_left_shoulder1" axis="2 -1 1" range="-60 85"/>
        <joint name="2a_left_shoulder2" axis="0 1 1"  range="-60 85"/>
        <geom name="2a_left_upper_arm" fromto="0 0 0 .16 .16 -.16" size=".04 .16"/>
        <body name="2a_left_lower_arm" pos=".18 .18 -.18">
          <joint name="2a_left_elbow" axis="0 -1 -1" range="-90 50" stiffness="0"/>
          <geom name="2a_left_lower_arm" fromto=".01 -.01 .01 .17 -.17 .17" size=".031"/>
          <body name="2a_left_hand" pos=".18 -.18 .18">
            <geom name="2a_left_hand" type="sphere" size=".04" zaxis="1 -1 1"/>
          </body>
        </body>
      </body>
    </body>
    <body name="3a_torso" pos="-1 -1 1.5" childclass="body3">
      <camera name="3a_back" pos="-3 0 1" xyaxes="0 -1 0 1 0 2" mode="trackcom"/>
      <camera name="3a_side" pos="0 -3 1" xyaxes="1 0 0 0 1 2" mode="trackcom"/>
      <freejoint name="3a_root"/>
      <geom name="3a_torso" fromto="0 -.07 0 0 .07 0" size=".07"/>
      <geom name="3a_upper_waist" fromto="-.01 -.06 -.12 -.01 .06 -.12" size=".06"/>
      <body name="3a_head" pos="0 0 .19">
        <geom name="3a_head" type="sphere" size=".09"/>
        <camera name="3a_egocentric" pos=".09 0 0" xyaxes="0 -1 0 .1 0 1" fovy="80"/>
      </body>
      <body name="3a_lower_waist" pos="-.01 0 -.26">
        <geom name="3a_lower_waist" fromto="0 -.06 0 0 .06 0" size=".06"/>
        <joint name="3a_abdomen_z" pos="0 0 .065" axis="0 0 1" range="-45 45" class="big_stiff_joint"/>
        <joint name="3a_abdomen_y" pos="0 0 .065" axis="0 1 0" range="-75 30" class="big_joint"/>
        <body name="3a_pelvis" pos="0 0 -.165">
          <joint name="3a_abdomen_x" pos="0 0 .1" axis="1 0 0" range="-35 35" class="big_joint"/>
          <geom name="3a_butt" fromto="-.02 -.07 0 -.02 .07 0" size=".09"/>
          <body name="3a_right_thigh" pos="0 -.1 -.04">
            <joint name="3a_right_hip_x" axis="1 0 0" range="-25 5" class="big_joint"/>
            <joint name="3a_right_hip_z" axis="0 0 1" range="-60 35" class="big_joint"/>
            <joint name="3a_right_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="3a_right_thigh" fromto="0 0 0 0 .01 -.34" size=".06"/>
            <body name="3a_right_shin" pos="0 .01 -.403">
              <joint name="3a_right_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="3a_right_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="3a_right_foot" pos="0 0 -.39">
                <joint name="3a_right_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="3a_right_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="3a_right_right_foot" fromto="-.07 -.02 0 .14 -.04 0" size=".027"/>
                <geom name="3a_left_right_foot" fromto="-.07 0 0 .14  .02 0" size=".027"/>
              </body>
            </body>
          </body>
          <body name="3a_left_thigh" pos="0 .1 -.04">
            <joint name="3a_left_hip_x" axis="-1 0 0" range="-25 5" class="big_joint"/>
            <joint name="3a_left_hip_z" axis="0 0 -1" range="-60 35" class="big_joint"/>
            <joint name="3a_left_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="3a_left_thigh" fromto="0 0 0 0 -.01 -.34" size=".06"/>
            <body name="3a_left_shin" pos="0 -.01 -.403">
              <joint name="3a_left_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="3a_left_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="3a_left_foot" pos="0 0 -.39">
                <joint name="3a_left_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="3a_left_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="3a_left_left_foot" fromto="-.07 .02 0 .14 .04 0" size=".027"/>
                <geom name="3a_right_left_foot" fromto="-.07 0 0 .14 -.02 0" size=".027"/>
              </body>
            </body>
          </body>
        </body>
      </body>
      <body name="3a_right_upper_arm" pos="0 -.17 .06">
        <joint name="3a_right_shoulder1" axis="2 1 1"  range="-85 60"/>
        <joint name="3a_right_shoulder2" axis="0 -1 1" range="-85 60"/>
        <geom name="3a_right_upper_arm" fromto="0 0 0 .16 -.16 -.16" size=".04 .16"/>
        <body name="3a_right_lower_arm" pos=".18 -.18 -.18">
          <joint name="3a_right_elbow" axis="0 -1 1" range="-90 50" stiffness="0"/>
          <geom name="3a_right_lower_arm" fromto=".01 .01 .01 .17 .17 .17" size=".031"/>
          <body name="3a_right_hand" pos=".18 .18 .18">
            <geom name="3a_right_hand" type="sphere" size=".04" zaxis="1 1 1"/>
          </body>
        </body>
      </body>
      <body name="3a_left_upper_arm" pos="0 .17 .06">
        <joint name="3a_left_shoulder1" axis="2 -1 1" range="-60 85"/>
        <joint name="3a_left_shoulder2" axis="0 1 1"  range="-60 85"/>
        <geom name="3a_left_upper_arm" fromto="0 0 0 .16 .16 -.16" size=".04 .16"/>
        <body name="3a_left_lower_arm" pos=".18 .18 -.18">
          <joint name="3a_left_elbow" axis="0 -1 -1" range="-90 50" stiffness="0"/>
          <geom name="3a_left_lower_arm" fromto=".01 -.01 .01 .17 -.17 .17" size=".031"/>
          <body name="3a_left_hand" pos=".18 -.18 .18">
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      <freejoint name="4a_root"/>
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            <joint name="4a_right_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
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              <geom name="4a_right_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="4a_right_foot" pos="0 0 -.39">
                <joint name="4a_right_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
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                <geom name="4a_right_right_foot" fromto="-.07 -.02 0 .14 -.04 0" size=".027"/>
                <geom name="4a_left_right_foot" fromto="-.07 0 0 .14  .02 0" size=".027"/>
              </body>
            </body>
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              <geom name="4a_left_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="4a_left_foot" pos="0 0 -.39">
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                <joint name="4a_left_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
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                <geom name="4a_right_left_foot" fromto="-.07 0 0 .14 -.02 0" size=".027"/>
              </body>
            </body>
          </body>
        </body>
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        <joint name="4a_right_shoulder2" axis="0 -1 1" range="-85 60"/>
        <geom name="4a_right_upper_arm" fromto="0 0 0 .16 -.16 -.16" size=".04 .16"/>
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          <body name="4a_right_hand" pos=".18 .18 .18">
            <geom name="4a_right_hand" type="sphere" size=".04" zaxis="1 1 1"/>
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        </body>
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        <joint name="4a_left_shoulder1" axis="2 -1 1" range="-60 85"/>
        <joint name="4a_left_shoulder2" axis="0 1 1"  range="-60 85"/>
        <geom name="4a_left_upper_arm" fromto="0 0 0 .16 .16 -.16" size=".04 .16"/>
        <body name="4a_left_lower_arm" pos=".18 .18 -.18">
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          <geom name="4a_left_lower_arm" fromto=".01 -.01 .01 .17 -.17 .17" size=".031"/>
          <body name="4a_left_hand" pos=".18 -.18 .18">
            <geom name="4a_left_hand" type="sphere" size=".04" zaxis="1 -1 1"/>
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        </body>
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      <freejoint name="5a_root"/>
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        <geom name="5a_head" type="sphere" size=".09"/>
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        <geom name="5a_lower_waist" fromto="0 -.06 0 0 .06 0" size=".06"/>
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        <joint name="5a_abdomen_y" pos="0 0 .065" axis="0 1 0" range="-75 30" class="big_joint"/>
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            <geom name="5a_right_thigh" fromto="0 0 0 0 .01 -.34" size=".06"/>
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              <joint name="5a_right_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="5a_right_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="5a_right_foot" pos="0 0 -.39">
                <joint name="5a_right_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="5a_right_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="5a_right_right_foot" fromto="-.07 -.02 0 .14 -.04 0" size=".027"/>
                <geom name="5a_left_right_foot" fromto="-.07 0 0 .14  .02 0" size=".027"/>
              </body>
            </body>
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            <joint name="5a_left_hip_x" axis="-1 0 0" range="-25 5" class="big_joint"/>
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            <joint name="5a_left_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="5a_left_thigh" fromto="0 0 0 0 -.01 -.34" size=".06"/>
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              <joint name="5a_left_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="5a_left_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="5a_left_foot" pos="0 0 -.39">
                <joint name="5a_left_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="5a_left_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="5a_left_left_foot" fromto="-.07 .02 0 .14 .04 0" size=".027"/>
                <geom name="5a_right_left_foot" fromto="-.07 0 0 .14 -.02 0" size=".027"/>
              </body>
            </body>
          </body>
        </body>
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        <joint name="5a_right_shoulder1" axis="2 1 1"  range="-85 60"/>
        <joint name="5a_right_shoulder2" axis="0 -1 1" range="-85 60"/>
        <geom name="5a_right_upper_arm" fromto="0 0 0 .16 -.16 -.16" size=".04 .16"/>
        <body name="5a_right_lower_arm" pos=".18 -.18 -.18">
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          <geom name="5a_right_lower_arm" fromto=".01 .01 .01 .17 .17 .17" size=".031"/>
          <body name="5a_right_hand" pos=".18 .18 .18">
            <geom name="5a_right_hand" type="sphere" size=".04" zaxis="1 1 1"/>
          </body>
        </body>
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      <body name="5a_left_upper_arm" pos="0 .17 .06">
        <joint name="5a_left_shoulder1" axis="2 -1 1" range="-60 85"/>
        <joint name="5a_left_shoulder2" axis="0 1 1"  range="-60 85"/>
        <geom name="5a_left_upper_arm" fromto="0 0 0 .16 .16 -.16" size=".04 .16"/>
        <body name="5a_left_lower_arm" pos=".18 .18 -.18">
          <joint name="5a_left_elbow" axis="0 -1 -1" range="-90 50" stiffness="0"/>
          <geom name="5a_left_lower_arm" fromto=".01 -.01 .01 .17 -.17 .17" size=".031"/>
          <body name="5a_left_hand" pos=".18 -.18 .18">
            <geom name="5a_left_hand" type="sphere" size=".04" zaxis="1 -1 1"/>
          </body>
        </body>
      </body>
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      <camera name="6a_back" pos="-3 0 1" xyaxes="0 -1 0 1 0 2" mode="trackcom"/>
      <camera name="6a_side" pos="0 -3 1" xyaxes="1 0 0 0 1 2" mode="trackcom"/>
      <freejoint name="6a_root"/>
      <geom name="6a_torso" fromto="0 -.07 0 0 .07 0" size=".07"/>
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        <geom name="6a_head" type="sphere" size=".09"/>
        <camera name="6a_egocentric" pos=".09 0 0" xyaxes="0 -1 0 .1 0 1" fovy="80"/>
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        <joint name="6a_abdomen_y" pos="0 0 .065" axis="0 1 0" range="-75 30" class="big_joint"/>
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            <geom name="6a_right_thigh" fromto="0 0 0 0 .01 -.34" size=".06"/>
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              <geom name="6a_right_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="6a_right_foot" pos="0 0 -.39">
                <joint name="6a_right_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="6a_right_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="6a_right_right_foot" fromto="-.07 -.02 0 .14 -.04 0" size=".027"/>
                <geom name="6a_left_right_foot" fromto="-.07 0 0 .14  .02 0" size=".027"/>
              </body>
            </body>
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            <joint name="6a_left_hip_x" axis="-1 0 0" range="-25 5" class="big_joint"/>
            <joint name="6a_left_hip_z" axis="0 0 -1" range="-60 35" class="big_joint"/>
            <joint name="6a_left_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
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              <geom name="6a_left_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="6a_left_foot" pos="0 0 -.39">
                <joint name="6a_left_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="6a_left_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="6a_left_left_foot" fromto="-.07 .02 0 .14 .04 0" size=".027"/>
                <geom name="6a_right_left_foot" fromto="-.07 0 0 .14 -.02 0" size=".027"/>
              </body>
            </body>
          </body>
        </body>
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      <body name="6a_right_upper_arm" pos="0 -.17 .06">
        <joint name="6a_right_shoulder1" axis="2 1 1"  range="-85 60"/>
        <joint name="6a_right_shoulder2" axis="0 -1 1" range="-85 60"/>
        <geom name="6a_right_upper_arm" fromto="0 0 0 .16 -.16 -.16" size=".04 .16"/>
        <body name="6a_right_lower_arm" pos=".18 -.18 -.18">
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          <geom name="6a_right_lower_arm" fromto=".01 .01 .01 .17 .17 .17" size=".031"/>
          <body name="6a_right_hand" pos=".18 .18 .18">
            <geom name="6a_right_hand" type="sphere" size=".04" zaxis="1 1 1"/>
          </body>
        </body>
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      <body name="6a_left_upper_arm" pos="0 .17 .06">
        <joint name="6a_left_shoulder1" axis="2 -1 1" range="-60 85"/>
        <joint name="6a_left_shoulder2" axis="0 1 1"  range="-60 85"/>
        <geom name="6a_left_upper_arm" fromto="0 0 0 .16 .16 -.16" size=".04 .16"/>
        <body name="6a_left_lower_arm" pos=".18 .18 -.18">
          <joint name="6a_left_elbow" axis="0 -1 -1" range="-90 50" stiffness="0"/>
          <geom name="6a_left_lower_arm" fromto=".01 -.01 .01 .17 -.17 .17" size=".031"/>
          <body name="6a_left_hand" pos=".18 -.18 .18">
            <geom name="6a_left_hand" type="sphere" size=".04" zaxis="1 -1 1"/>
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        </body>
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      <camera name="7a_side" pos="0 -3 1" xyaxes="1 0 0 0 1 2" mode="trackcom"/>
      <freejoint name="7a_root"/>
      <geom name="7a_torso" fromto="0 -.07 0 0 .07 0" size=".07"/>
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        <geom name="7a_head" type="sphere" size=".09"/>
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              <geom name="7a_right_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="7a_right_foot" pos="0 0 -.39">
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                <joint name="7a_right_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="7a_right_right_foot" fromto="-.07 -.02 0 .14 -.04 0" size=".027"/>
                <geom name="7a_left_right_foot" fromto="-.07 0 0 .14  .02 0" size=".027"/>
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              <joint name="7a_left_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="7a_left_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
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                <joint name="7a_left_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
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                <geom name="7a_left_left_foot" fromto="-.07 .02 0 .14 .04 0" size=".027"/>
                <geom name="7a_right_left_foot" fromto="-.07 0 0 .14 -.02 0" size=".027"/>
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        <joint name="7a_right_shoulder2" axis="0 -1 1" range="-85 60"/>
        <geom name="7a_right_upper_arm" fromto="0 0 0 .16 -.16 -.16" size=".04 .16"/>
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          <geom name="7a_right_lower_arm" fromto=".01 .01 .01 .17 .17 .17" size=".031"/>
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            <geom name="7a_right_hand" type="sphere" size=".04" zaxis="1 1 1"/>
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        </body>
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      <body name="7a_left_upper_arm" pos="0 .17 .06">
        <joint name="7a_left_shoulder1" axis="2 -1 1" range="-60 85"/>
        <joint name="7a_left_shoulder2" axis="0 1 1"  range="-60 85"/>
        <geom name="7a_left_upper_arm" fromto="0 0 0 .16 .16 -.16" size=".04 .16"/>
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          <joint name="7a_left_elbow" axis="0 -1 -1" range="-90 50" stiffness="0"/>
          <geom name="7a_left_lower_arm" fromto=".01 -.01 .01 .17 -.17 .17" size=".031"/>
          <body name="7a_left_hand" pos=".18 -.18 .18">
            <geom name="7a_left_hand" type="sphere" size=".04" zaxis="1 -1 1"/>
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      <freejoint name="8a_root"/>
      <geom name="8a_torso" fromto="0 -.07 0 0 .07 0" size=".07"/>
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        <geom name="8a_head" type="sphere" size=".09"/>
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      <body name="8a_lower_waist" pos="-.01 0 -.26">
        <geom name="8a_lower_waist" fromto="0 -.06 0 0 .06 0" size=".06"/>
        <joint name="8a_abdomen_z" pos="0 0 .065" axis="0 0 1" range="-45 45" class="big_stiff_joint"/>
        <joint name="8a_abdomen_y" pos="0 0 .065" axis="0 1 0" range="-75 30" class="big_joint"/>
        <body name="8a_pelvis" pos="0 0 -.165">
          <joint name="8a_abdomen_x" pos="0 0 .1" axis="1 0 0" range="-35 35" class="big_joint"/>
          <geom name="8a_butt" fromto="-.02 -.07 0 -.02 .07 0" size=".09"/>
          <body name="8a_right_thigh" pos="0 -.1 -.04">
            <joint name="8a_right_hip_x" axis="1 0 0" range="-25 5" class="big_joint"/>
            <joint name="8a_right_hip_z" axis="0 0 1" range="-60 35" class="big_joint"/>
            <joint name="8a_right_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="8a_right_thigh" fromto="0 0 0 0 .01 -.34" size=".06"/>
            <body name="8a_right_shin" pos="0 .01 -.403">
              <joint name="8a_right_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="8a_right_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="8a_right_foot" pos="0 0 -.39">
                <joint name="8a_right_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="8a_right_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="8a_right_right_foot" fromto="-.07 -.02 0 .14 -.04 0" size=".027"/>
                <geom name="8a_left_right_foot" fromto="-.07 0 0 .14  .02 0" size=".027"/>
              </body>
            </body>
          </body>
          <body name="8a_left_thigh" pos="0 .1 -.04">
            <joint name="8a_left_hip_x" axis="-1 0 0" range="-25 5" class="big_joint"/>
            <joint name="8a_left_hip_z" axis="0 0 -1" range="-60 35" class="big_joint"/>
            <joint name="8a_left_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="8a_left_thigh" fromto="0 0 0 0 -.01 -.34" size=".06"/>
            <body name="8a_left_shin" pos="0 -.01 -.403">
              <joint name="8a_left_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="8a_left_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="8a_left_foot" pos="0 0 -.39">
                <joint name="8a_left_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="8a_left_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="8a_left_left_foot" fromto="-.07 .02 0 .14 .04 0" size=".027"/>
                <geom name="8a_right_left_foot" fromto="-.07 0 0 .14 -.02 0" size=".027"/>
              </body>
            </body>
          </body>
        </body>
      </body>
      <body name="8a_right_upper_arm" pos="0 -.17 .06">
        <joint name="8a_right_shoulder1" axis="2 1 1"  range="-85 60"/>
        <joint name="8a_right_shoulder2" axis="0 -1 1" range="-85 60"/>
        <geom name="8a_right_upper_arm" fromto="0 0 0 .16 -.16 -.16" size=".04 .16"/>
        <body name="8a_right_lower_arm" pos=".18 -.18 -.18">
          <joint name="8a_right_elbow" axis="0 -1 1" range="-90 50" stiffness="0"/>
          <geom name="8a_right_lower_arm" fromto=".01 .01 .01 .17 .17 .17" size=".031"/>
          <body name="8a_right_hand" pos=".18 .18 .18">
            <geom name="8a_right_hand" type="sphere" size=".04" zaxis="1 1 1"/>
          </body>
        </body>
      </body>
      <body name="8a_left_upper_arm" pos="0 .17 .06">
        <joint name="8a_left_shoulder1" axis="2 -1 1" range="-60 85"/>
        <joint name="8a_left_shoulder2" axis="0 1 1"  range="-60 85"/>
        <geom name="8a_left_upper_arm" fromto="0 0 0 .16 .16 -.16" size=".04 .16"/>
        <body name="8a_left_lower_arm" pos=".18 .18 -.18">
          <joint name="8a_left_elbow" axis="0 -1 -1" range="-90 50" stiffness="0"/>
          <geom name="8a_left_lower_arm" fromto=".01 -.01 .01 .17 -.17 .17" size=".031"/>
          <body name="8a_left_hand" pos=".18 -.18 .18">
            <geom name="8a_left_hand" type="sphere" size=".04" zaxis="1 -1 1"/>
          </body>
        </body>
      </body>
    </body>
    <body name="9a_torso" pos="-1 -4 1.5" childclass="body9">
      <camera name="9a_back" pos="-3 0 1" xyaxes="0 -1 0 1 0 2" mode="trackcom"/>
      <camera name="9a_side" pos="0 -3 1" xyaxes="1 0 0 0 1 2" mode="trackcom"/>
      <freejoint name="9a_root"/>
      <geom name="9a_torso" fromto="0 -.07 0 0 .07 0" size=".07"/>
      <geom name="9a_upper_waist" fromto="-.01 -.06 -.12 -.01 .06 -.12" size=".06"/>
      <body name="9a_head" pos="0 0 .19">
        <geom name="9a_head" type="sphere" size=".09"/>
        <camera name="9a_egocentric" pos=".09 0 0" xyaxes="0 -1 0 .1 0 1" fovy="80"/>
      </body>
      <body name="9a_lower_waist" pos="-.01 0 -.26">
        <geom name="9a_lower_waist" fromto="0 -.06 0 0 .06 0" size=".06"/>
        <joint name="9a_abdomen_z" pos="0 0 .065" axis="0 0 1" range="-45 45" class="big_stiff_joint"/>
        <joint name="9a_abdomen_y" pos="0 0 .065" axis="0 1 0" range="-75 30" class="big_joint"/>
        <body name="9a_pelvis" pos="0 0 -.165">
          <joint name="9a_abdomen_x" pos="0 0 .1" axis="1 0 0" range="-35 35" class="big_joint"/>
          <geom name="9a_butt" fromto="-.02 -.07 0 -.02 .07 0" size=".09"/>
          <body name="9a_right_thigh" pos="0 -.1 -.04">
            <joint name="9a_right_hip_x" axis="1 0 0" range="-25 5" class="big_joint"/>
            <joint name="9a_right_hip_z" axis="0 0 1" range="-60 35" class="big_joint"/>
            <joint name="9a_right_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="9a_right_thigh" fromto="0 0 0 0 .01 -.34" size=".06"/>
            <body name="9a_right_shin" pos="0 .01 -.403">
              <joint name="9a_right_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="9a_right_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="9a_right_foot" pos="0 0 -.39">
                <joint name="9a_right_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="9a_right_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="9a_right_right_foot" fromto="-.07 -.02 0 .14 -.04 0" size=".027"/>
                <geom name="9a_left_right_foot" fromto="-.07 0 0 .14  .02 0" size=".027"/>
              </body>
            </body>
          </body>
          <body name="9a_left_thigh" pos="0 .1 -.04">
            <joint name="9a_left_hip_x" axis="-1 0 0" range="-25 5" class="big_joint"/>
            <joint name="9a_left_hip_z" axis="0 0 -1" range="-60 35" class="big_joint"/>
            <joint name="9a_left_hip_y" axis="0 1 0" range="-110 20" class="big_stiff_joint"/>
            <geom name="9a_left_thigh" fromto="0 0 0 0 -.01 -.34" size=".06"/>
            <body name="9a_left_shin" pos="0 -.01 -.403">
              <joint name="9a_left_knee" pos="0 0 .02" axis="0 -1 0" range="-160 2"/>
              <geom name="9a_left_shin" fromto="0 0 0 0 0 -.3"  size=".049"/>
              <body name="9a_left_foot" pos="0 0 -.39">
                <joint name="9a_left_ankle_y" pos="0 0 .08" axis="0 1 0" range="-50 50" stiffness="6"/>
                <joint name="9a_left_ankle_x" pos="0 0 .04" axis="1 0 .5" range="-50 50" stiffness="3"/>
                <geom name="9a_left_left_foot" fromto="-.07 .02 0 .14 .04 0" size=".027"/>
                <geom name="9a_right_left_foot" fromto="-.07 0 0 .14 -.02 0" size=".027"/>
              </body>
            </body>
          </body>
        </body>
      </body>
      <body name="9a_right_upper_arm" pos="0 -.17 .06">
        <joint name="9a_right_shoulder1" axis="2 1 1"  range="-85 60"/>
        <joint name="9a_right_shoulder2" axis="0 -1 1" range="-85 60"/>
        <geom name="9a_right_upper_arm" fromto="0 0 0 .16 -.16 -.16" size=".04 .16"/>
        <body name="9a_right_lower_arm" pos=".18 -.18 -.18">
          <joint name="9a_right_elbow" axis="0 -1 1" range="-90 50" stiffness="0"/>
          <geom name="9a_right_lower_arm" fromto=".01 .01 .01 .17 .17 .17" size=".031"/>
          <body name="9a_right_hand" pos=".18 .18 .18">
            <geom name="9a_right_hand" type="sphere" size=".04" zaxis="1 1 1"/>
          </body>
        </body>
      </body>
      <body name="9a_left_upper_arm" pos="0 .17 .06">
        <joint name="9a_left_shoulder1" axis="2 -1 1" range="-60 85"/>
        <joint name="9a_left_shoulder2" axis="0 1 1"  range="-60 85"/>
        <geom name="9a_left_upper_arm" fromto="0 0 0 .16 .16 -.16" size=".04 .16"/>
        <body name="9a_left_lower_arm" pos=".18 .18 -.18">
          <joint name="9a_left_elbow" axis="0 -1 -1" range="-90 50" stiffness="0"/>
          <geom name="9a_left_lower_arm" fromto=".01 -.01 .01 .17 -.17 .17" size=".031"/>
          <body name="9a_left_hand" pos=".18 -.18 .18">
            <geom name="9a_left_hand" type="sphere" size=".04" zaxis="1 -1 1"/>
          </body>
        </body>
      </body>
    </body>
  </worldbody>
  <actuator>
    <motor gear="40"  joint="1a_abdomen_y"/>
    <motor gear="40"  joint="1a_abdomen_z"/>
    <motor gear="40"  joint="1a_abdomen_x"/>
    <motor gear="40"  joint="1a_right_hip_x"/>
    <motor gear="40"  joint="1a_right_hip_z"/>
    <motor gear="120" joint="1a_right_hip_y"/>
    <motor gear="80"  joint="1a_right_knee"/>
    <motor gear="20"  joint="1a_right_ankle_x"/>
    <motor gear="20"  joint="1a_right_ankle_y"/>
    <motor gear="40"  joint="1a_left_hip_x"/>
    <motor gear="40"  joint="1a_left_hip_z"/>
    <motor gear="120" joint="1a_left_hip_y"/>
    <motor gear="80"  joint="1a_left_knee"/>
    <motor gear="20"  joint="1a_left_ankle_x"/>
    <motor gear="20"  joint="1a_left_ankle_y"/>
    <motor gear="20"  joint="1a_right_shoulder1"/>
    <motor gear="20"  joint="1a_right_shoulder2"/>
    <motor gear="40"  joint="1a_right_elbow"/>
    <motor gear="20"  joint="1a_left_shoulder1"/>
    <motor gear="20"  joint="1a_left_shoulder2"/>
    <motor gear="40"  joint="1a_left_elbow"/>
  </actuator>
  <actuator>
    <motor gear="40"  joint="2a_abdomen_y"/>
    <motor gear="40"  joint="2a_abdomen_z"/>
    <motor gear="40"  joint="2a_abdomen_x"/>
    <motor gear="40"  joint="2a_right_hip_x"/>
    <motor gear="40"  joint="2a_right_hip_z"/>
    <motor gear="120" joint="2a_right_hip_y"/>
    <motor gear="80"  joint="2a_right_knee"/>
    <motor gear="20"  joint="2a_right_ankle_x"/>
    <motor gear="20"  joint="2a_right_ankle_y"/>
    <motor gear="40"  joint="2a_left_hip_x"/>
    <motor gear="40"  joint="2a_left_hip_z"/>
    <motor gear="120" joint="2a_left_hip_y"/>
    <motor gear="80"  joint="2a_left_knee"/>
    <motor gear="20"  joint="2a_left_ankle_x"/>
    <motor gear="20"  joint="2a_left_ankle_y"/>
    <motor gear="20"  joint="2a_right_shoulder1"/>
    <motor gear="20"  joint="2a_right_shoulder2"/>
    <motor gear="40"  joint="2a_right_elbow"/>
    <motor gear="20"  joint="2a_left_shoulder1"/>
    <motor gear="20"  joint="2a_left_shoulder2"/>
    <motor gear="40"  joint="2a_left_elbow"/>
  </actuator>
  <actuator>
    <motor gear="40"  joint="3a_abdomen_y"/>
    <motor gear="40"  joint="3a_abdomen_z"/>
    <motor gear="40"  joint="3a_abdomen_x"/>
    <motor gear="40"  joint="3a_right_hip_x"/>
    <motor gear="40"  joint="3a_right_hip_z"/>
    <motor gear="120" joint="3a_right_hip_y"/>
    <motor gear="80"  joint="3a_right_knee"/>
    <motor gear="20"  joint="3a_right_ankle_x"/>
    <motor gear="20"  joint="3a_right_ankle_y"/>
    <motor gear="40"  joint="3a_left_hip_x"/>
    <motor gear="40"  joint="3a_left_hip_z"/>
    <motor gear="120" joint="3a_left_hip_y"/>
    <motor gear="80"  joint="3a_left_knee"/>
    <motor gear="20"  joint="3a_left_ankle_x"/>
    <motor gear="20"  joint="3a_left_ankle_y"/>
    <motor gear="20"  joint="3a_right_shoulder1"/>
    <motor gear="20"  joint="3a_right_shoulder2"/>
    <motor gear="40"  joint="3a_right_elbow"/>
    <motor gear="20"  joint="3a_left_shoulder1"/>
    <motor gear="20"  joint="3a_left_shoulder2"/>
    <motor gear="40"  joint="3a_left_elbow"/>
  </actuator>
  <actuator>
    <motor gear="40"  joint="4a_abdomen_y"/>
    <motor gear="40"  joint="4a_abdomen_z"/>
    <motor gear="40"  joint="4a_abdomen_x"/>
    <motor gear="40"  joint="4a_right_hip_x"/>
    <motor gear="40"  joint="4a_right_hip_z"/>
    <motor gear="120" joint="4a_right_hip_y"/>
    <motor gear="80"  joint="4a_right_knee"/>
    <motor gear="20"  joint="4a_right_ankle_x"/>
    <motor gear="20"  joint="4a_right_ankle_y"/>
    <motor gear="40"  joint="4a_left_hip_x"/>
    <motor gear="40"  joint="4a_left_hip_z"/>
    <motor gear="120" joint="4a_left_hip_y"/>
    <motor gear="80"  joint="4a_left_knee"/>
    <motor gear="20"  joint="4a_left_ankle_x"/>
    <motor gear="20"  joint="4a_left_ankle_y"/>
    <motor gear="20"  joint="4a_right_shoulder1"/>
    <motor gear="20"  joint="4a_right_shoulder2"/>
    <motor gear="40"  joint="4a_right_elbow"/>
    <motor gear="20"  joint="4a_left_shoulder1"/>
    <motor gear="20"  joint="4a_left_shoulder2"/>
    <motor gear="40"  joint="4a_left_elbow"/>
  </actuator>
  <actuator>
    <motor gear="40"  joint="5a_abdomen_y"/>
    <motor gear="40"  joint="5a_abdomen_z"/>
    <motor gear="40"  joint="5a_abdomen_x"/>
    <motor gear="40"  joint="5a_right_hip_x"/>
    <motor gear="40"  joint="5a_right_hip_z"/>
    <motor gear="120" joint="5a_right_hip_y"/>
    <motor gear="80"  joint="5a_right_knee"/>
    <motor gear="20"  joint="5a_right_ankle_x"/>
    <motor gear="20"  joint="5a_right_ankle_y"/>
    <motor gear="40"  joint="5a_left_hip_x"/>
    <motor gear="40"  joint="5a_left_hip_z"/>
    <motor gear="120" joint="5a_left_hip_y"/>
    <motor gear="80"  joint="5a_left_knee"/>
    <motor gear="20"  joint="5a_left_ankle_x"/>
    <motor gear="20"  joint="5a_left_ankle_y"/>
    <motor gear="20"  joint="5a_right_shoulder1"/>
    <motor gear="20"  joint="5a_right_shoulder2"/>
    <motor gear="40"  joint="5a_right_elbow"/>
    <motor gear="20"  joint="5a_left_shoulder1"/>
    <motor gear="20"  joint="5a_left_shoulder2"/>
    <motor gear="40"  joint="5a_left_elbow"/>
  </actuator>
  <actuator>
    <motor gear="40"  joint="6a_abdomen_y"/>
    <motor gear="40"  joint="6a_abdomen_z"/>
    <motor gear="40"  joint="6a_abdomen_x"/>
    <motor gear="40"  joint="6a_right_hip_x"/>
    <motor gear="40"  joint="6a_right_hip_z"/>
    <motor gear="120" joint="6a_right_hip_y"/>
    <motor gear="80"  joint="6a_right_knee"/>
    <motor gear="20"  joint="6a_right_ankle_x"/>
    <motor gear="20"  joint="6a_right_ankle_y"/>
    <motor gear="40"  joint="6a_left_hip_x"/>
    <motor gear="40"  joint="6a_left_hip_z"/>
    <motor gear="120" joint="6a_left_hip_y"/>
    <motor gear="80"  joint="6a_left_knee"/>
    <motor gear="20"  joint="6a_left_ankle_x"/>
    <motor gear="20"  joint="6a_left_ankle_y"/>
    <motor gear="20"  joint="6a_right_shoulder1"/>
    <motor gear="20"  joint="6a_right_shoulder2"/>
    <motor gear="40"  joint="6a_right_elbow"/>
    <motor gear="20"  joint="6a_left_shoulder1"/>
    <motor gear="20"  joint="6a_left_shoulder2"/>
    <motor gear="40"  joint="6a_left_elbow"/>
  </actuator>
  <actuator>
    <motor gear="40"  joint="7a_abdomen_y"/>
    <motor gear="40"  joint="7a_abdomen_z"/>
    <motor gear="40"  joint="7a_abdomen_x"/>
    <motor gear="40"  joint="7a_right_hip_x"/>
    <motor gear="40"  joint="7a_right_hip_z"/>
    <motor gear="120" joint="7a_right_hip_y"/>
    <motor gear="80"  joint="7a_right_knee"/>
    <motor gear="20"  joint="7a_right_ankle_x"/>
    <motor gear="20"  joint="7a_right_ankle_y"/>
    <motor gear="40"  joint="7a_left_hip_x"/>
    <motor gear="40"  joint="7a_left_hip_z"/>
    <motor gear="120" joint="7a_left_hip_y"/>
    <motor gear="80"  joint="7a_left_knee"/>
    <motor gear="20"  joint="7a_left_ankle_x"/>
    <motor gear="20"  joint="7a_left_ankle_y"/>
    <motor gear="20"  joint="7a_right_shoulder1"/>
    <motor gear="20"  joint="7a_right_shoulder2"/>
    <motor gear="40"  joint="7a_right_elbow"/>
    <motor gear="20"  joint="7a_left_shoulder1"/>
    <motor gear="20"  joint="7a_left_shoulder2"/>
    <motor gear="40"  joint="7a_left_elbow"/>
  </actuator>
  <actuator>
    <motor gear="40"  joint="8a_abdomen_y"/>
    <motor gear="40"  joint="8a_abdomen_z"/>
    <motor gear="40"  joint="8a_abdomen_x"/>
    <motor gear="40"  joint="8a_right_hip_x"/>
    <motor gear="40"  joint="8a_right_hip_z"/>
    <motor gear="120" joint="8a_right_hip_y"/>
    <motor gear="80"  joint="8a_right_knee"/>
    <motor gear="20"  joint="8a_right_ankle_x"/>
    <motor gear="20"  joint="8a_right_ankle_y"/>
    <motor gear="40"  joint="8a_left_hip_x"/>
    <motor gear="40"  joint="8a_left_hip_z"/>
    <motor gear="120" joint="8a_left_hip_y"/>
    <motor gear="80"  joint="8a_left_knee"/>
    <motor gear="20"  joint="8a_left_ankle_x"/>
    <motor gear="20"  joint="8a_left_ankle_y"/>
    <motor gear="20"  joint="8a_right_shoulder1"/>
    <motor gear="20"  joint="8a_right_shoulder2"/>
    <motor gear="40"  joint="8a_right_elbow"/>
    <motor gear="20"  joint="8a_left_shoulder1"/>
    <motor gear="20"  joint="8a_left_shoulder2"/>
    <motor gear="40"  joint="8a_left_elbow"/>
  </actuator>
  <actuator>
    <motor gear="40"  joint="9a_abdomen_y"/>
    <motor gear="40"  joint="9a_abdomen_z"/>
    <motor gear="40"  joint="9a_abdomen_x"/>
    <motor gear="40"  joint="9a_right_hip_x"/>
    <motor gear="40"  joint="9a_right_hip_z"/>
    <motor gear="120" joint="9a_right_hip_y"/>
    <motor gear="80"  joint="9a_right_knee"/>
    <motor gear="20"  joint="9a_right_ankle_x"/>
    <motor gear="20"  joint="9a_right_ankle_y"/>
    <motor gear="40"  joint="9a_left_hip_x"/>
    <motor gear="40"  joint="9a_left_hip_z"/>
    <motor gear="120" joint="9a_left_hip_y"/>
    <motor gear="80"  joint="9a_left_knee"/>
    <motor gear="20"  joint="9a_left_ankle_x"/>
    <motor gear="20"  joint="9a_left_ankle_y"/>
    <motor gear="20"  joint="9a_right_shoulder1"/>
    <motor gear="20"  joint="9a_right_shoulder2"/>
    <motor gear="40"  joint="9a_right_elbow"/>
    <motor gear="20"  joint="9a_left_shoulder1"/>
    <motor gear="20"  joint="9a_left_shoulder2"/>
    <motor gear="40"  joint="9a_left_elbow"/>
  </actuator>
 </mujoco>
@@ -156,7 +156,7 @@
                    diaginertia="1.28092e-06 1.12092e-06 5.3e-07"/>
                  <joint name="rh_FFJ1" class="middle_distal"/>
                  <geom class="plastic_visual" mesh="f_distal_pst"/>
-                  <geom class="plastic_collision" type="mesh" mesh="f_distal_pst_214"/>
+                  <geom class="plastic_collision" type="mesh" mesh="f_distal_pst_214" contype="0" conaffinity="2"/>
                </body>
              </body>
            </body>
@@ -181,7 +181,7 @@
                    diaginertia="1.28092e-06 1.12092e-06 5.3e-07"/>
                  <joint name="rh_MFJ1" class="middle_distal"/>
                  <geom class="plastic_visual" mesh="f_distal_pst"/>
-                  <geom class="plastic_collision" type="mesh" mesh="f_distal_pst_214"/>
+                  <geom class="plastic_collision" type="mesh" mesh="f_distal_pst_214" contype="0" conaffinity="2"/>
                </body>
              </body>
            </body>
@@ -206,7 +206,7 @@
                    diaginertia="1.28092e-06 1.12092e-06 5.3e-07"/>
                  <joint name="rh_RFJ1" class="middle_distal"/>
                  <geom class="plastic_visual" mesh="f_distal_pst"/>
-                  <geom class="plastic_collision" type="mesh" mesh="f_distal_pst_214"/>
+                  <geom class="plastic_collision" type="mesh" mesh="f_distal_pst_214" contype="0" conaffinity="2"/>
                </body>
              </body>
            </body>
@@ -236,7 +236,7 @@
                      diaginertia="1.28092e-06 1.12092e-06 5.3e-07"/>
                    <joint name="rh_LFJ1" class="middle_distal"/>
                    <geom class="plastic_visual" mesh="f_distal_pst"/>
-                    <geom class="plastic_collision" type="mesh" mesh="f_distal_pst_214"/>
+                    <geom class="plastic_collision" type="mesh" mesh="f_distal_pst_214" contype="0" conaffinity="2"/>
                  </body>
                </body>
              </body>
@@ -266,7 +266,7 @@
                      diaginertia="2.37794e-06 2.27794e-06 1e-06"/>
                    <joint name="rh_THJ1" class="thdistal"/>
                    <geom class="plastic_visual" mesh="th_distal_pst"/>
-                    <geom class="plastic_collision" type="mesh" mesh="th_distal_pst_190"/>
+                    <geom class="plastic_collision" type="mesh" mesh="th_distal_pst_190" contype="0" conaffinity="2"/>
                  </body>
                </body>
              </body>
@@ -14,110 +14,67 @@
 # ==============================================================================
 """Run benchmarks on various devices."""
-import os
+from typing import Sequence
 import time
 from typing import Sequence, Tuple
 from absl import app
 from absl import flags
 from etils import epath
 import jax
 import mujoco
 from mujoco import mjx
-FLAGS = flags.FLAGS
+_MJCF = flags.DEFINE_string('mjcf', None, 'path to model', required=True)
-
+_BASE_PATH = flags.DEFINE_string(
-flags.DEFINE_string('mjcf', None, 'path to model', required=True)
+    'base_path', None, 'base path, defaults to mujoco.mjx resource path'
-flags.DEFINE_integer('nstep', 1000, 'number of steps per rollout')
+)
-flags.DEFINE_integer('batch_size', 1024, 'number of parallel rollouts')
+_NSTEP = flags.DEFINE_integer('nstep', 1000, 'number of steps per rollout')
-flags.DEFINE_integer('unroll', 1, 'loop unroll length')
+_BATCH_SIZE = flags.DEFINE_integer(
-flags.DEFINE_enum('solver', 'cg', ['cg', 'newton'], 'constraint solver')
+    'batch_size', 1024, 'number of parallel rollouts'
-flags.DEFINE_integer('iterations', 1, 'number of solver iterations')
+)
-flags.DEFINE_integer('ls_iterations', 4, 'number of linesearch iterations')
+_UNROLL = flags.DEFINE_integer('unroll', 1, 'loop unroll length')
-flags.DEFINE_enum('output', 'text', ['text', 'tsv'], 'format to print results')
+_SOLVER = flags.DEFINE_enum(
-
+    'solver', 'cg', ['cg', 'newton'], 'constraint solver'
-
+)
-def _measure(fn, *args) -> Tuple[float, float]:
+_ITERATIONS = flags.DEFINE_integer(
-  """Reports jit time and op time for a function."""
+    'iterations', 1, 'number of solver iterations'
-
+)
-  beg = time.perf_counter()
+_LS_ITERATIONS = flags.DEFINE_integer(
-  compiled_fn = fn.lower(*args).compile()
+    'ls_iterations', 4, 'number of linesearch iterations'
-  end = time.perf_counter()
+)
-  jit_time = end - beg
+_OUTPUT = flags.DEFINE_enum(
-
+    'output', 'text', ['text', 'tsv'], 'format to print results'
-  beg = time.perf_counter()
+)
  result = compiled_fn(*args)
  jax.block_until_ready(result)
  end = time.perf_counter()
  run_time = end - beg
  return jit_time, run_time
 def _main(argv: Sequence[str]):
-  """Benchmark a model."""
+  """Runs testpeed function."""
-
+  base_path = _BASE_PATH.value or epath.resource_path('mujoco.mjx')
-  xla_flags = os.environ.get('XLA_FLAGS', '')
+  f = base_path / 'test_data' / _MJCF.value
  xla_flags += ' --xla_gpu_triton_gemm_any=True'
  os.environ['XLA_FLAGS'] = xla_flags
  f = epath.resource_path('mujoco.mjx') / 'test_data' / FLAGS.mjcf
  m = mujoco.MjModel.from_xml_path(f.as_posix())
  m.opt.solver = {
      'cg': mujoco.mjtSolver.mjSOL_CG,
      'newton': mujoco.mjtSolver.mjSOL_NEWTON,
  }[FLAGS.solver.lower()]
  m.opt.iterations = FLAGS.iterations
  m.opt.ls_iterations = FLAGS.ls_iterations
  m = mjx.put_model(m)
-  if FLAGS.output == 'text':
+  print(f'Rolling out {_NSTEP.value} steps at dt = {m.opt.timestep:.3f}...')
-    print(f"Rolling out {FLAGS.nstep} steps at dt = {m.opt.timestep:.3f}...")
+  jit_time, run_time, steps = mjx.benchmark(
      m,
      _NSTEP.value,
      _BATCH_SIZE.value,
      _UNROLL.value,
      _SOLVER.value,
      _ITERATIONS.value,
      _LS_ITERATIONS.value,
  )
-  @jax.pmap
+  name = argv[0]
-  def init(key):
+  if _OUTPUT.value == 'text':
    key = jax.random.split(key, FLAGS.batch_size // jax.device_count())
    @jax.vmap
    def random_init(key):
      d = mjx.make_data(m)
      qvel = 0.01 * jax.random.normal(key, shape=(m.nv,))
      d = d.replace(qvel=qvel)
      return d
    return random_init(key)
  key = jax.random.split(jax.random.key(0), jax.device_count())
  d = init(key)
  jax.block_until_ready(d)
  @jax.pmap
  def unroll(d):
    @jax.vmap
    def step(d, _):
      d = mjx.step(m, d)
      return d, None
    d, _ = jax.lax.scan(step, d, None, length=FLAGS.nstep, unroll=FLAGS.unroll)
    return d
  jit_time, run_time = _measure(unroll, d)
  steps = FLAGS.nstep * FLAGS.batch_size
  if FLAGS.output == 'text':
    print(f"""
-Summary for {FLAGS.batch_size} parallel rollouts
+Summary for {_BATCH_SIZE.value} parallel rollouts
 Total JIT time: {jit_time:.2f} s
 Total simulation time: {run_time:.2f} s
 Total steps per second: { steps / run_time:.0f}
 Total realtime factor: { steps * m.opt.timestep / run_time:.2f} x
 Total time per step: { 1e6 * run_time / steps:.2f} µs""")
-  elif FLAGS.output == 'tsv':
+  elif _OUTPUT.value == 'tsv':
-    name = argv[0].split('/')[-1].replace('testspeed_', '')
+    name = name.split('/')[-1].replace('testspeed_', '')
-    print(f"{name}\tjit: {jit_time:.2f}s\tsteps/second: {steps / run_time:.0f}")
+    print(f'{name}\tjit: {jit_time:.2f}s\tsteps/second: {steps / run_time:.0f}')
 def main():
@@ -367,7 +367,7 @@
    "rng = jax.random.split(rng, 4096)\n",
    "batch = jax.vmap(lambda rng: mjx_data.replace(qpos=jax.random.uniform(rng, (1,))))(rng)\n",
    "\n",
-    "jit_step = jax.vmap(mjx.step, in_axes=(None, 0))\n",
+    "jit_step = jax.jit(jax.vmap(mjx.step, in_axes=(None, 0)))\n",
    "batch = jit_step(mjx_model, batch)\n",
    "\n",
    "print(batch.qpos)"
@@ -234,10 +234,10 @@
    "$$\n",
    "\\begin{aligned}\n",
    "x^* &= \\arg \\min_x f(x)\\\\\n",
-    "\\textrm{s.t.} &\\quad l \\succcurlyeq x \\succcurlyeq u\n",
+    "\\textrm{s.t.} &\\quad l \\preccurlyeq x \\preccurlyeq u\n",
    "\\end{aligned}\n",
    "$$\n",
-    "Where $l$ and $u$ are respectively lower and upper bound vectors and the inequalities $l \\succcurlyeq x \\succcurlyeq u$ are read elementwise. Solving for the minimizing $\\delta x$ is now a bit more involved than solving a linear system, and the optimization method is now referred to as [Sequential Quadratic Programming](https://en.wikipedia.org/wiki/Sequential_quadratic_programming) (SQP). Fortunately MuJoCo has an efficient box-constrained QP solver: the [mju_boxQP](https://mujoco.readthedocs.io/en/latest/APIreference/APIfunctions.html#mju-boxqp) function."
+    "Where $l$ and $u$ are respectively lower and upper bound vectors and the inequalities $l \\preccurlyeq x \\preccurlyeq u$ are read elementwise. Solving for the minimizing $\\delta x$ is now a bit more involved than solving a linear system, and the optimization method is now referred to as [Sequential Quadratic Programming](https://en.wikipedia.org/wiki/Sequential_quadratic_programming) (SQP). Fortunately MuJoCo has an efficient box-constrained QP solver: the [mju_boxQP](https://mujoco.readthedocs.io/en/latest/APIreference/APIfunctions.html#mju-boxqp) function."
   ]
  },
  {
@@ -623,7 +623,7 @@ class MuJoCoBindingsTest(parameterized.TestCase):
    self.assertEqual(struct, struct2)
    self.assertNotEqual(struct, 3)
-    self.assertNotEqual(struct, None)
+    self.assertIsNotNone(struct)
    # mutable structs shouldn't declare __hash__
    with self.assertRaises(TypeError):
@@ -705,7 +705,8 @@ class MuJoCoBindingsTest(parameterized.TestCase):
    # Check that the output argument must have the correct dtype.
    with self.assertRaises(TypeError):
-      mujoco.mju_rotVecQuat(vec, quat, res=np.zeros(3, int))
+      res = np.zeros(3, np.int32)
      mujoco.mju_rotVecQuat(res, vec, quat)
  def test_getsetstate(self):  # pylint: disable=invalid-name
    mujoco.mj_step(self.model, self.data)
@@ -850,8 +851,7 @@ Euler integrator, semi-implicit in velocity.
    self.assertEqual(mujoco.mjtEnableBit.mjENBL_OVERRIDE, 1<<0)
    self.assertEqual(mujoco.mjtEnableBit.mjENBL_ENERGY, 1<<1)
    self.assertEqual(mujoco.mjtEnableBit.mjENBL_FWDINV, 1<<2)
-    self.assertEqual(mujoco.mjtEnableBit.mjENBL_SENSORNOISE, 1<<4)
+    self.assertEqual(mujoco.mjtEnableBit.mjNENABLE, 6)
    self.assertEqual(mujoco.mjtEnableBit.mjNENABLE, 7)
    self.assertEqual(mujoco.mjtGeom.mjGEOM_PLANE, 0)
    self.assertEqual(mujoco.mjtGeom.mjGEOM_HFIELD, 1)
    self.assertEqual(mujoco.mjtGeom.mjGEOM_SPHERE, 2)
@@ -0,0 +1,71 @@
 #usda 1.0
 (
    defaultPrim = "World"
    doc = """Generated from Composed Stage of root layer 
 """
    endTimeCode = 1
    startTimeCode = 0
    timeCodesPerSecond = 24
    upAxis = "Z"
 )
 def Xform "World"
 {
    def Xform "Light_Xform_0"
    {
        double3 xformOp:translate
        uniform token[] xformOpOrder = ["xformOp:translate"]
        def SphereLight "Light_0"
        {
            bool inputs:normalize = 1
            float inputs:radius = 0.3
            bool treatAsPoint = 0
        }
    }
    def Xform "CubeMesh_Xform_white_box"
    {
        matrix4d xformOp:transform.timeSamples = {
            0: ( (0, 0, 0, 0), (0, 0, 0, 0), (0, 0, 0, 0), (0, 0, 0, 1) ),
        }
        uniform token[] xformOpOrder = ["xformOp:transform"]
        def Mesh "CubeMesh_white_box" (
            apiSchemas = ["MaterialBindingAPI"]
        )
        {
            int[] faceVertexCounts = [3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3]
            int[] faceVertexIndices = [4, 7, 5, 4, 6, 7, 0, 2, 4, 2, 6, 4, 0, 1, 2, 1, 3, 2, 1, 5, 7, 1, 7, 3, 2, 3, 7, 2, 7, 6, 0, 4, 1, 1, 4, 5]
            rel material:binding = </World/_materials/Material_white_box>
            point3f[] points = [(-1, -1, -1), (1, -1, -1), (-1, -1, 1), (1, -1, 1), (-1, 1, -1), (1, 1, -1), (-1, 1, 1), (1, 1, 1)]
            texCoord2f[] primvars:UVMap = [] (
                interpolation = "faceVarying"
            )
            int[] primvars:UVMap:indices = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35]
            uniform token subdivisionScheme = "none"
            token visibility.timeSamples = {
                0: "inherited",
            }
        }
    }
    def "_materials"
    {
        def Material "Material_white_box"
        {
            token outputs:surface.connect = </World/_materials/Material_white_box/Principled_BSDF.outputs:surface>
            def Shader "Principled_BSDF"
            {
                uniform token info:id = "UsdPreviewSurface"
                color3f inputs:diffuseColor = (1, 1, 1)
                float inputs:metallic = 0.5
                float inputs:opacity = 1
                float inputs:roughness = 0.5
                token outputs:surface
            }
        }
    }
 }
@@ -15,6 +15,7 @@
 from typing import List, Optional, Tuple
 import mujoco
 import mujoco.usd.utils
 import numpy as np
 # TODO: b/288149332 - Remove once USD Python Binding works well with pytype.
@@ -38,7 +39,7 @@ class USDMesh:
      geom: mujoco.MjvGeom,
      obj_name: str,
      dataid: int,
-      rgba: Tuple[int, ...] = (1, 1, 1, 1),
+      rgba: np.ndarray = np.array([1, 1, 1, 1]),
      texture_file: Optional[str] = None,
  ):
    self.stage = stage
@@ -236,7 +237,7 @@ class USDPrimitiveMesh:
      stage: Usd.Stage,
      geom: mujoco.MjvGeom,
      obj_name: str,
-      rgba: Tuple[int, ...] = (1, 1, 1, 1),
+      rgba: np.ndarray = np.array([1, 1, 1, 1]),
      texture_file: Optional[str] = None,
  ):
    self.stage = stage
@@ -245,7 +246,10 @@ class USDPrimitiveMesh:
    self.rgba = rgba
    self.texture_file = texture_file
    self.usd_prim = Usd.Prim()
    self.usd_mesh = UsdGeom.Mesh()
    self.prim_mesh = None
    self.transform_op = Gf.Matrix4d(1.)
  def _set_refinement_properties(self):
    self.usd_prim.GetAttribute("subdivisionScheme").Set("none")
@@ -374,119 +378,6 @@ class USDPrimitiveMesh:
      self.usd_prim.GetAttribute("visibility").Set("invisible", frame)
 class USDPrimitive:
  def __init__(
      self,
      stage: Usd.Stage,
      geom: mujoco.MjvGeom,
      obj_name: str,
      rgba: Tuple[int, ...] = (1, 1, 1, 1),
      texture_file: Optional[str] = None,
  ):
    self.stage = stage
    self.geom = geom
    self.obj_name = obj_name
    self.rgba = rgba
    self.texture_file = texture_file
  def _set_refinement_properties(self):
    self.usd_prim.GetAttribute("subdivisionScheme").Set("none")
  def _attach_material(self):
    mtl_path = Sdf.Path(f"/World/_materials/Material_{self.obj_name}")
    mtl = UsdShade.Material.Define(self.stage, mtl_path)
    if self.texture_file:
      bsdf_shader = UsdShade.Shader.Define(
          self.stage, mtl_path.AppendPath("Principled_BSDF")
      )
      image_shader = UsdShade.Shader.Define(
          self.stage, mtl_path.AppendPath("Image_Texture")
      )
      uvmap_shader = UsdShade.Shader.Define(
          self.stage, mtl_path.AppendPath("uvmap")
      )
      # settings the bsdf shader attributes
      bsdf_shader.CreateIdAttr("UsdPreviewSurface")
      bsdf_shader.CreateInput(
          "diffuseColor", Sdf.ValueTypeNames.Color3f
      ).ConnectToSource(image_shader.ConnectableAPI(), "rgb")
      bsdf_shader.CreateInput("opacity", Sdf.ValueTypeNames.Float).Set(
          float(self.rgba[-1])
      )
      bsdf_shader.CreateInput("metallic", Sdf.ValueTypeNames.Float).Set(
          self.geom.shininess
      )
      bsdf_shader.CreateInput("roughness", Sdf.ValueTypeNames.Float).Set(
          1.0 - self.geom.shininess
      )
      mtl.CreateSurfaceOutput().ConnectToSource(
          bsdf_shader.ConnectableAPI(), "surface"
      )
      self.usd_primitive_shape.GetPrim().ApplyAPI(UsdShade.MaterialBindingAPI)
      UsdShade.MaterialBindingAPI(self.usd_primitive_shape).Bind(mtl)
      # setting the image texture attributes
      image_shader.CreateIdAttr("UsdUVTexture")
      image_shader.CreateInput("file", Sdf.ValueTypeNames.Asset).Set(
          self.texture_file
      )
      image_shader.CreateInput(
          "sourceColorSpace", Sdf.ValueTypeNames.Token
      ).Set("sRGB")
      image_shader.CreateInput("st", Sdf.ValueTypeNames.Float2).ConnectToSource(
          uvmap_shader.ConnectableAPI(), "result"
      )
      image_shader.CreateOutput("rgb", Sdf.ValueTypeNames.Float3)
      # setting uvmap shader attributes
      uvmap_shader.CreateIdAttr("UsdPrimvarReader_float2")
      uvmap_shader.CreateInput("varname", Sdf.ValueTypeNames.Token).Set("UVMap")
      uvmap_shader.CreateOutput("results", Sdf.ValueTypeNames.Float2)
    else:
      bsdf_shader = UsdShade.Shader.Define(
          self.stage, mtl_path.AppendPath("Principled_BSDF")
      )
      # settings the bsdf shader attributes
      bsdf_shader.CreateIdAttr("UsdPreviewSurface")
      bsdf_shader.CreateInput("diffuseColor", Sdf.ValueTypeNames.Color3f).Set(
          tuple(self.rgba[:3])
      )
      bsdf_shader.CreateInput("opacity", Sdf.ValueTypeNames.Float).Set(
          float(self.rgba[-1])
      )
      bsdf_shader.CreateInput("metallic", Sdf.ValueTypeNames.Float).Set(
          self.geom.shininess
      )
      bsdf_shader.CreateInput("roughness", Sdf.ValueTypeNames.Float).Set(
          1.0 - self.geom.shininess
      )
    mtl.CreateSurfaceOutput().ConnectToSource(
        bsdf_shader.ConnectableAPI(), "surface"
    )
    self.usd_primitive_shape.GetPrim().ApplyAPI(UsdShade.MaterialBindingAPI)
    UsdShade.MaterialBindingAPI(self.usd_primitive_shape).Bind(mtl)
  def update(self, pos: np.ndarray, mat: np.ndarray, visible: bool, frame: int):
    transformation_mat = mujoco.usd.utils.create_transform_matrix(
        rotation_matrix=mat, translation_vector=pos
    ).T
    self.transform_op.Set(Gf.Matrix4d(transformation_mat.tolist()), frame)
    self.update_visibility(visible, frame)
  def update_visibility(self, visible: bool, frame: int):
    if visible:
      self.usd_prim.GetAttribute("visibility").Set("inherited", frame)
    else:
      self.usd_prim.GetAttribute("visibility").Set("invisible", frame)
 class USDCapsule(USDPrimitive):
  def __init__(
@@ -494,7 +385,7 @@ class USDCapsule(USDPrimitive):
      stage: Usd.Stage,
      geom: mujoco.MjvGeom,
      obj_name: str,
-      rgba: Tuple[int, ...] = (1, 1, 1, 1),
+      rgba: np.ndarray = np.array([1, 1, 1, 1]),
      texture_file: Optional[str] = None,
  ):
@@ -514,7 +405,7 @@ class USDCapsule(USDPrimitive):
    self._set_size_attributes()
    self._attach_material()
-    self._set_refinement_properties()
+    # self._set_refinement_properties()
  def _set_size_attributes(self):
    self.usd_primitive_shape.GetRadiusAttr().Set(float(self.geom.size[0]))
@@ -530,7 +421,7 @@ class USDEllipsoid(USDPrimitive):
      stage: Usd.Stage,
      geom: mujoco.MjvGeom,
      obj_name: str,
-      rgba: Tuple[int, ...] = (1, 1, 1, 1),
+      rgba: np.ndarray = np.array([1, 1, 1, 1]),
      texture_file: Optional[str] = None,
  ):
@@ -550,7 +441,7 @@ class USDEllipsoid(USDPrimitive):
    self._set_size_attributes()
    self._attach_material()
-    self._set_refinement_properties()
+    # self._set_refinement_properties()
  def _set_size_attributes(self):
    self.scale_op.Set(Gf.Vec3d(self.geom.size.tolist()))
@@ -563,7 +454,7 @@ class USDCubeMesh(USDPrimitiveMesh):
      stage: Usd.Stage,
      geom: mujoco.MjvGeom,
      obj_name: str,
-      rgba: Tuple[int, ...] = (1, 1, 1, 1),
+      rgba: np.ndarray = np.array([1, 1, 1, 1]),
      texture_file: Optional[str] = None,
  ):
@@ -579,8 +470,6 @@ class USDCubeMesh(USDPrimitiveMesh):
        width=self.geom.size[0] * 2,
        height=self.geom.size[1] * 2,
        depth=self.geom.size[2] * 2,
        create_uv_map=True,
        map_texture_to_each_face=True,
    )
    self.prim_mesh.translate(-self.prim_mesh.get_center())
@@ -617,7 +506,7 @@ class USDSphereMesh(USDPrimitiveMesh):
      stage: Usd.Stage,
      geom: mujoco.MjvGeom,
      obj_name: str,
-      rgba: Tuple[int, ...] = (1, 1, 1, 1),
+      rgba: np.ndarray = np.array([1, 1, 1, 1]),
      texture_file: Optional[str] = None,
  ):
@@ -667,7 +556,7 @@ class USDCylinderMesh(USDPrimitiveMesh):
      stage: Usd.Stage,
      geom: mujoco.MjvGeom,
      obj_name: str,
-      rgba: Tuple[int, ...] = (1, 1, 1, 1),
+      rgba: np.ndarray = np.array([1, 1, 1, 1]),
      texture_file: Optional[str] = None,
  ):
@@ -719,7 +608,7 @@ class USDPlaneMesh(USDPrimitiveMesh):
      stage: Usd.Stage,
      geom: mujoco.MjvGeom,
      obj_name: str,
-      rgba: Tuple[int, ...] = (1, 1, 1, 1),
+      rgba: np.ndarray = np.array([1, 1, 1, 1]),
      texture_file: Optional[str] = None,
  ):
@@ -814,7 +703,6 @@ class USDDomeLight:
    self.usd_light.GetNormalizeAttr().Set(True)
  def update(self, intensity: int, color: np.ndarray, frame: int):
    self.usd_light.GetIntensityAttr().Set(intensity)
    self.usd_light.GetExposureAttr().Set(0.0)
    self.usd_light.GetColorAttr().Set(Gf.Vec3d(color.tolist()))
@@ -14,6 +14,6 @@ if __name__ == "__main__":
  exp.update_scene(d)
-  exp.save_scene(filetype="usd")
+  exp.save_scene(filetype="usda")
@@ -15,6 +15,7 @@
 import os
 import mujoco
 import mujoco.usd.component as component_module
 import numpy as np
 import scipy
 import termcolor
@@ -235,7 +236,7 @@ class USDExporter:
    # handles meshes in scene
    if geom.type == mujoco.mjtGeom.mjGEOM_MESH:
-      usd_geom = mujoco.usd.component.USDMesh(
+      usd_geom = component_module.USDMesh(
          stage=self.stage,
          model=self.model,
          geom=geom,
@@ -245,7 +246,7 @@ class USDExporter:
          texture_file=texture_file,
      )
    elif geom.type == mujoco.mjtGeom.mjGEOM_PLANE:
-      usd_geom = mujoco.usd.component.USDPlaneMesh(
+      usd_geom = component_module.USDPlaneMesh(
          stage=self.stage,
          geom=geom,
          obj_name=geom_name,
@@ -253,7 +254,7 @@ class USDExporter:
          texture_file=texture_file,
      )
    elif geom.type == mujoco.mjtGeom.mjGEOM_SPHERE:
-      usd_geom = mujoco.usd.component.USDSphereMesh(
+      usd_geom = component_module.USDSphereMesh(
          stage=self.stage,
          geom=geom,
          obj_name=geom_name,
@@ -261,7 +262,7 @@ class USDExporter:
          texture_file=texture_file,
      )
    elif geom.type == mujoco.mjtGeom.mjGEOM_CAPSULE:
-      usd_geom = mujoco.usd.component.USDCapsule(
+      usd_geom = component_module.USDCapsule(
          stage=self.stage,
          geom=geom,
          obj_name=geom_name,
@@ -269,7 +270,7 @@ class USDExporter:
          texture_file=texture_file,
      )
    elif geom.type == mujoco.mjtGeom.mjGEOM_ELLIPSOID:
-      usd_geom = mujoco.usd.component.USDEllipsoid(
+      usd_geom = component_module.USDEllipsoid(
          stage=self.stage,
          geom=geom,
          obj_name=geom_name,
@@ -277,7 +278,7 @@ class USDExporter:
          texture_file=texture_file,
      )
    elif geom.type == mujoco.mjtGeom.mjGEOM_CYLINDER:
-      usd_geom = mujoco.usd.component.USDCylinderMesh(
+      usd_geom = component_module.USDCylinderMesh(
          stage=self.stage,
          geom=geom,
          obj_name=geom_name,
@@ -285,7 +286,7 @@ class USDExporter:
          texture_file=texture_file,
      )
    elif geom.type == mujoco.mjtGeom.mjGEOM_BOX:
-      usd_geom = mujoco.usd.component.USDCubeMesh(
+      usd_geom = component_module.USDCubeMesh(
          stage=self.stage,
          geom=geom,
          obj_name=geom_name,
@@ -331,7 +332,8 @@ class USDExporter:
    for i in range(self.scene.nlight):
      light = self.scene.lights[i]
      if not np.allclose(light.pos, [0, 0, 0]):
-        self.usd_lights.append(mujoco.usd.component.USDSphereLight(stage=self.stage, obj_name=i))
+        self.usd_lights.append
        (component_module.USDSphereLight(stage=self.stage, obj_name=str(i)))
      else:
        self.usd_lights.append(None)
@@ -342,7 +344,7 @@ class USDExporter:
      if np.allclose(light.pos, [0, 0, 0]):
        continue
-      if self.usd_lights[i] is None:
+      if i >= len(self.usd_lights) or self.usd_lights[i] is None:
        continue
      self.usd_lights[i].update(
@@ -356,7 +358,8 @@ class USDExporter:
    self.usd_cameras = []
    if self.camera_names is not None:
      for name in self.camera_names:
-        self.usd_cameras.append(mujoco.usd.USDCamera(stage=self.stage, obj_name=name))
+        self.usd_cameras.append(
            component_module.USDCamera(stage=self.stage, obj_name=name))
  def _update_cameras(
      self,
@@ -372,7 +375,8 @@ class USDExporter:
          data, scene_option=scene_option, camera=camera_name
      )
-      avg_camera = mujoco.mjv_averageCamera(self.scene.camera[0], self.scene.camera[1])
+      avg_camera = mujoco.mjv_averageCamera(
          self.scene.camera[0], self.scene.camera[1])
      forward = avg_camera.forward
      up = avg_camera.up
@@ -396,11 +400,12 @@ class USDExporter:
  ):
    if light_type == "sphere":
-      new_light = mujoco.usd.component.USDSphereLight(stage=self.stage, obj_name=obj_name, radius=radius)
+      new_light = component_module.USDSphereLight(stage=self.stage, obj_name=str(objid), radius=radius)
-      new_light.update(pos=pos, intensity=intensity, color=color, frame=0)
+      new_light.update(pos=np.array(pos), intensity=intensity, color=color, frame=0)
    elif light_type == "dome":
-      new_light = mujoco.usd.component.USDDomeLight(stage=self.stage, obj_name=obj_name)
+      new_light = component_module.USDDomeLight(
          stage=self.stage, obj_name=str(objid))
      new_light.update(intensity=intensity, color=color, frame=0)
@@ -410,11 +415,12 @@ class USDExporter:
      rotation_xyz: List[float],
      obj_name: Optional[str] = "camera_1",
  ):
-    new_camera = mujoco.usd.component.USDCamera(stage=self.stage, obj_name=obj_name)
+    new_camera = component_module.USDCamera(
        stage=self.stage, obj_name=str(objid))
    r = scipy.spatial.transform.Rotation.from_euler(
        "xyz", rotation_xyz, degrees=True)
-    new_camera.update(cam_pos=pos, cam_mat=r.as_matrix(), frame=0)
+    new_camera.update(cam_pos=np.array(pos), cam_mat=r.as_matrix(), frame=0)
  def save_scene(self, filetype: str = "usd"):
    self.stage.SetEndTimeCode(self.frame_count)
@@ -0,0 +1,70 @@
 # Copyright 2024 DeepMind Technologies Limited
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
 # You may obtain a copy of the License at
 #
 #     http://www.apache.org/licenses/LICENSE-2.0
 #
 # Unless required by applicable law or agreed to in writing, software
 # distributed under the License is distributed on an "AS IS" BASIS,
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
 # ==============================================================================
 """Tests for the MuJoCo USD Exporter."""
 import logging
 import os
 import mujoco
 from absl.testing import absltest
 from etils import epath
 # Open3D and USD are not fully supported on all MuJoCo architectures.
 # pylint: disable=python.style(g-import-not-at-top)
 execute_test = True
 try:
  from mujoco.usd import exporter as exporter_module
  from pxr import Usd
 except ImportError:
  logging.warning('Skipping test due to missing import')
  execute_test = False
 # pylint: enable=python.style(g-import-not-at-top)
 class ExporterTest(absltest.TestCase):
  def test_usd_export(self):
    if not execute_test:
      return
    output_dir = os.getenv('TEST_UNDECLARED_OUTPUTS_DIR')
    xml = """
 <mujoco>
  <worldbody>
    <camera name="closeup" pos="0 -6 0" xyaxes="1 0 0 0 1 100"/>
    <geom name="white_box" type="box" size="1 1 1" rgba="1 1 1 1"/>
  </worldbody>
 </mujoco>
 """
    model = mujoco.MjModel.from_xml_string(xml)
    data = mujoco.MjData(model)
    exporter = exporter_module.USDExporter(
        model,
        output_directory_name="mujoco_usdpkg",
        output_directory_root=output_dir,
    )
    exporter.update_scene(data)
    exporter.save_scene("export.usda")
    with open(os.path.join(
        output_dir, "mujoco_usdpkg/frames", "frame_1_.export.usda"), "r") as f:
      golden_path = os.path.join(
          epath.resource_path("mujoco"), "testdata", "usd_golden.usda")
      with open(golden_path, "r") as golden_file:
        self.assertEqual(f.read(), golden_file.read())
 if __name__ == "__main__":
  absltest.main()
@@ -169,7 +169,10 @@ def _file_loader(path: str) -> _LoaderWithPathType:
  """Loads an MJCF model from file path."""
  def load(path=path) -> Tuple[mujoco.MjModel, mujoco.MjData, str]:
-    m = mujoco.MjModel.from_xml_path(path)
+    if len(path) >= 4 and path[-4:] == '.mjb':
      m = mujoco.MjModel.from_binary_path(path)
    else:
      m = mujoco.MjModel.from_xml_path(path)
    d = mujoco.MjData(m)
    return m, d, path
@@ -199,6 +202,9 @@ def _reload(
    path = load_tuple[2] if len(load_tuple) == 3 else ''
    simulate.load(m, d, path)
    # Make sure any load_error message is cleared
    simulate.load_error = ''
    if notify_loaded:
      notify_loaded()
@@ -638,7 +638,7 @@ int mjc_BoxBox(const mjModel* M, const mjData* D, mjContact* con, int g1, int g2
  mju_sub3(tmp1, pos1, pos2);
  mju_rotVecMatT(pos12, tmp1, mat2);
-  mju_mulMatTMat(rot, mat1, mat2, 3, 3, 3);
+  mju_mulMatTMat3(rot, mat1, mat2);
  mju_transpose(rott, rot, 3, 3);
  for (i = 0; i < 9; i++)
@@ -804,7 +804,7 @@ int mjc_BoxBox(const mjModel* M, const mjData* D, mjContact* con, int g1, int g2
 }
  if (q2) {
-    mju_mulMatMatT(r, rotmore, rot, 3, 3, 3);
+    mju_mulMatMatT3(r, rotmore, rot);
    // mju_rotVecMat(p,pos12,rotmore);
    // mju_rotVecMat(tmp1,size2,rotmore);
@@ -956,7 +956,7 @@ int mjc_BoxBox(const mjModel* M, const mjData* D, mjContact* con, int g1, int g2
  }
-  mju_mulMatMatT(r, q2 ? mat2 : mat1, rotmore, 3, 3, 3);
+  mju_mulMatMatT3(r, q2 ? mat2 : mat1, rotmore);
  mju_copy3(p, q2 ? pos2 : pos1);
  tmp2[0] = (q2 ? -1 : 1) * r[2];
@@ -1319,7 +1319,7 @@ edgeedge:
    }
  }
-  mju_mulMatMatT(r, mat1, rotmore, 3, 3, 3);
+  mju_mulMatMatT3(r, mat1, rotmore);
  mju_rotVecMat(tmp1, rnorm, r);
@@ -318,7 +318,7 @@ static void mju_rotateFrame(const mjtNum origin[3], const mjtNum rot[9],
  mjtNum mat[9], vec[3], rel[3];
  // rotate frame: xmat = rot*xmat
-  mju_mulMatMat(mat, rot, xmat, 3, 3, 3);
+  mju_mulMatMat3(mat, rot, xmat);
  mju_copy(xmat, mat, 9);
  // vector to rotation origin: rel = origin - xpos
@@ -682,7 +682,7 @@ int mjc_ConvexHField(const mjModel* m, const mjData* d,
  }
  // express geom2 mat in heightfield frame
-  mju_mulMatTMat(mat, mat1, mat2, 3, 3, 3);
+  mju_mulMatTMat3(mat, mat1, mat2);
  //------------------------------------- AABB computation, box-box test
@@ -140,9 +140,18 @@ static void geomGradient(mjtNum gradient[3], const mjModel* m, const mjData* d,
    b[2] = a[2] / size[2];
    mjtNum k0 = mju_norm3(a);
    mjtNum k1 = mju_norm3(b);
-    gradient[0] = a[0]*(2.*k0 - 1.) / k1 + k0*(k0 - 1.) * b[0]/(k1*k1);
+    mjtNum invK0 = 1. / k0;
-    gradient[1] = a[1]*(2.*k0 - 1.) / k1 + k0*(k0 - 1.) * b[1]/(k1*k1);
+    mjtNum invK1 = 1. / k1;
-    gradient[2] = a[2]*(2.*k0 - 1.) / k1 + k0*(k0 - 1.) * b[2]/(k1*k1);
+    mjtNum gk0[3] = {b[0]*invK0, b[1]*invK0, b[2]*invK0};
    mjtNum gk1[3] = {b[0]*invK1/(size[0]*size[0]),
                     b[1]*invK1/(size[1]*size[1]),
                     b[2]*invK1/(size[2]*size[2])};
    mjtNum df_dk0 = (2.*k0 - 1.) * invK1;
    mjtNum df_dk1 = k0*(k0 - 1.) * invK1 * invK1;
    gradient[0] = gk0[0]*df_dk0 - gk1[0]*df_dk1;
    gradient[1] = gk0[1]*df_dk0 - gk1[1]*df_dk1;
    gradient[2] = gk0[2]*df_dk0 - gk1[2]*df_dk1;
    mju_normalize3(gradient);
    break;
  case mjGEOM_CYLINDER:
    c = mju_sqrt(x[0]*x[0]+x[1]*x[1]);
@@ -251,7 +251,7 @@ void mjd_subQuat(const mjtNum qa[4], const mjtNum qb[4], mjtNum Da[9], mjtNum Db
  // add term linear in K * K
  mjtNum KK[9];
-  mju_mulMatMat(KK, K, K, 3, 3, 3);
+  mju_mulMatMat3(KK, K, K);
  mjtNum coef = 1.0 - (half_angle < 6e-8 ? 1.0 : half_angle / mju_tan(half_angle));
  mju_addToScl(Da_tmp, KK, coef, 9);
@@ -243,6 +243,19 @@ static mjtNum nextActivation(const mjModel* m, const mjData* d,
 // clamp vector to range
 static void clampVec(mjtNum* vec, const mjtNum* range, const mjtByte* limited, int n,
                      const int* index) {
  for (int i=0; i < n; i++) {
    int j = index ? index[i] : i;
    if (limited[i]) {
      vec[j] = mju_clip(vec[j], range[2*i], range[2*i + 1]);
    }
  }
 }
 // (qpos, qvel, ctrl, act) => (qfrc_actuator, actuator_force, act_dot)
 void mj_fwdActuation(const mjModel* m, mjData* d) {
  TM_START;
@@ -262,18 +275,9 @@ void mj_fwdActuation(const mjModel* m, mjData* d) {
  // local, clamped copy of ctrl
  mj_markStack(d);
  mjtNum *ctrl = mj_stackAllocNum(d, nu);
-  if (mjDISABLED(mjDSBL_CLAMPCTRL)) {
+  mju_copy(ctrl, d->ctrl, nu);
-    mju_copy(ctrl, d->ctrl, nu);
+  if (!mjDISABLED(mjDSBL_CLAMPCTRL)) {
-  } else {
+    clampVec(ctrl, m->actuator_ctrlrange, m->actuator_ctrllimited, nu, NULL);
    for (int i=0; i < nu; i++) {
      // clamp ctrl
      if (m->actuator_ctrllimited[i]) {
        mjtNum *ctrlrange = m->actuator_ctrlrange + 2*i;
        ctrl[i] = mju_clip(d->ctrl[i], ctrlrange[0], ctrlrange[1]);
      } else {
        ctrl[i] = d->ctrl[i];
      }
    }
  }
  // check controls, set all to 0 if any are bad
@@ -459,26 +463,48 @@ void mj_fwdActuation(const mjModel* m, mjData* d) {
  }
  // clamp actuator_force
-  for (int i=0; i < nu; i++) {
+  clampVec(force, m->actuator_forcerange, m->actuator_forcelimited, nu, NULL);
    if (m->actuator_forcelimited[i]) {
      mjtNum *forcerange = m->actuator_forcerange + 2*i;
      force[i] = mju_clip(force[i], forcerange[0], forcerange[1]);
    }
  }
  // qfrc_actuator = moment' * force
  mju_mulMatTVec(d->qfrc_actuator, moment, force, nu, nv);
-  // clamp qfrc_actuator
+  // actuator-level gravity compensation
-  int njnt = m->njnt;
+  if (!mjDISABLED(mjDSBL_GRAVITY) && mju_norm3(m->opt.gravity)) {
-  for (int i=0; i < njnt; i++) {
+    int njnt = m->njnt;
-    if (m->jnt_actfrclimited[i]) {
+    for (int i=0; i < njnt; i++) {
-      mjtNum *forcerange = m->jnt_actfrcrange + 2*i;
+      // skip if gravcomp added as passive force
-      mjtNum *qfrc = d->qfrc_actuator + m->jnt_dofadr[i];
+      if (!m->jnt_actgravcomp[i]) {
-      qfrc[0] = mju_clip(qfrc[0], forcerange[0], forcerange[1]);
+        continue;
      }
      // get number of dofs for this joint
      int dofnum;
      switch (m->jnt_type[i]) {
      case mjJNT_HINGE:
      case mjJNT_SLIDE:
        dofnum = 1;
        break;
      case mjJNT_BALL:
        dofnum = 3;
        break;
      case mjJNT_FREE:
        dofnum = 6;
        break;
      }
      // add gravcomp force
      int dofadr = m->jnt_dofadr[i];
      for (int j=0; j < dofnum; j++) {
        d->qfrc_actuator[dofadr+j] += d->qfrc_gravcomp[dofadr+j];
      }
    }
  }
  // clamp qfrc_actuator to joint-level actuator force limits
  clampVec(d->qfrc_actuator, m->jnt_actfrcrange, m->jnt_actfrclimited, m->njnt, m->jnt_dofadr);
  mj_freeStack(d);
  TM_END(mjTIMER_ACTUATION);
 }
@@ -489,13 +515,13 @@ void mj_fwdActuation(const mjModel* m, mjData* d) {
 void mj_fwdAcceleration(const mjModel* m, mjData* d) {
  int nv = m->nv;
-  // qforce = sum of all non-constraint forces
+  // qfrc_smooth = sum of all non-constraint forces
  mju_sub(d->qfrc_smooth, d->qfrc_passive, d->qfrc_bias, nv);    // qfrc_bias is negative
  mju_addTo(d->qfrc_smooth, d->qfrc_applied, nv);
  mju_addTo(d->qfrc_smooth, d->qfrc_actuator, nv);
  mj_xfrcAccumulate(m, d, d->qfrc_smooth);
-  // qacc_smooth = M \ qfr_smooth
+  // qacc_smooth = M \ qfrc_smooth
  mj_solveM(m, d, d->qacc_smooth, d->qfrc_smooth, 1);
 }
@@ -706,9 +732,10 @@ void mj_fwdConstraint(const mjModel* m, mjData* d) {
 // advance state and time given activation derivatives, acceleration, and optional velocity
 static void mj_advance(const mjModel* m, mjData* d,
                       const mjtNum* act_dot, const mjtNum* qacc, const mjtNum* qvel) {
-  // advance activations and clamp
+  // advance activations
  if (m->na && !mjDISABLED(mjDSBL_ACTUATION)) {
-    for (int i=0; i < m->nu; i++) {
+    int nu = m->nu;
    for (int i=0; i < nu; i++) {
      int actadr = m->actuator_actadr[i];
      int actadr_end = actadr + m->actuator_actnum[i];
      for (int j=actadr; j < actadr_end; j++) {
@@ -255,8 +255,39 @@ void mj_passive(const mjModel* m, mjData* d) {
  // add passive forces into qfrc_passive
  mju_add(d->qfrc_passive, d->qfrc_spring, d->qfrc_damper, nv);
  if (has_gravcomp) mju_addTo(d->qfrc_passive, d->qfrc_gravcomp, nv);
  if (has_fluid) mju_addTo(d->qfrc_passive, d->qfrc_fluid, nv);
  if (has_gravcomp) {
    int njnt = m->njnt;
    for (int i=0; i < njnt; i++) {
      // skip if gravcomp added via actuators
      if (m->jnt_actgravcomp[i]) {
        continue;
      }
      // get number of dofs for this joint
      int dofnum;
      switch (m->jnt_type[i]) {
      case mjJNT_HINGE:
      case mjJNT_SLIDE:
        dofnum = 1;
        break;
      case mjJNT_BALL:
        dofnum = 3;
        break;
      case mjJNT_FREE:
        dofnum = 6;
        break;
      }
      // add gravcomp force
      int dofadr = m->jnt_dofadr[i];
      for (int j=0; j < dofnum; j++) {
        d->qfrc_passive[dofadr+j] += d->qfrc_gravcomp[dofadr+j];
      }
    }
  }
  // user callback: add custom passive forces
  if (mjcb_passive) {
@@ -361,14 +361,6 @@ void mj_printFormattedModel(const mjModel* m, const char* filename, const char*
  }
  if (m->nbody) fprintf(fp, "\n");
  // BVHs
  for (int i=0; i < m->nbvh; i++) {
    fprintf(fp, "\nBVH %d:\n", i);
    object_class = &m->nbvh;
    MJMODEL_POINTERS
  }
  if (m->nbvh) fprintf(fp, "\n");
  // joints
  for (int i=0; i < m->njnt; i++) {
    fprintf(fp, "\nJOINT %d:\n", i);
@@ -732,6 +724,15 @@ void mj_printFormattedModel(const mjModel* m, const char* filename, const char*
 #undef X
  // BVHs
  fprintf(fp, "BVH:\n");
  fprintf(fp, "  %-8s%-8s%-8s%-10s%-s\n","id", "depth", "nodeid", "child[0]" ,"child[1]");
  for (int i=0; i < m->nbvh; i++) {
    fprintf(fp, "  %-8d%-8d% -8d% -10d% -d\n",
            i, m->bvh_depth[i], m->bvh_nodeid[i], m->bvh_child[2*i], m->bvh_child[2*i+1]);
  }
  fprintf(fp, "\n");
  if (filename) {
    fclose(fp);
  }
@@ -34,6 +34,7 @@
 #include <mujoco/mjplugin.h>
 #include "engine/engine_plugin.h"
 #include "engine/engine_util_errmem.h"
 #include "engine/engine_util_misc.h"
 // internal helper for mju_fileToMemory (closes fp automatically)
 static void* _fileToMemory(FILE* fp, const char* filename, size_t* filesize);
@@ -113,10 +114,8 @@ mjResource* mju_openResource(const char* name, char* error, size_t error_sz) {
    memcpy(&spec->mtime, &file_stat.st_mtime, sizeof(time_t));
  } else {
    memset(&spec->mtime, 0, sizeof(time_t));
    resource->timestamp[0] = '\0';
  }
-  strftime(resource->timestamp, 512, "%Y-%m-%d-%H:%M:%S",
+  mju_encodeBase64(resource->timestamp, (uint8_t*) &spec->mtime, sizeof(time_t));
           localtime(&(spec->mtime)));
  return resource;
 }
@@ -199,19 +198,6 @@ void mju_getResourceDir(mjResource* resource, const char** dir, int* ndir) {
 // modified callback for OS filesystem
 static int mju_isModifiedFile(const char* name, const file_spec* spec) {
  if (spec != NULL) {
    struct stat file_stat;
    if (stat(name, &file_stat) == 0) {
      return difftime(spec->mtime, file_stat.st_mtime) < 0;
    }
  }
  return 1;  // modified (default)
 }
 // return 0 if the resource's timestamp matches the provided timestamp
 // return > 0 if the the resource is younger than the given timestamp
 // return < 0 if the resource is older than the given timestamp
@@ -224,7 +210,18 @@ int mju_isModifiedResource(const mjResource* resource, const char* timestamp) {
    return 1;  // default (modified)
  }
-  return mju_isModifiedFile(resource->name, (file_spec*) resource->data);
+  // fallback to OS filesystem
  if (mju_isValidBase64(timestamp) != sizeof(time_t)) {
    return 1;  // error (assume modified)
  }
  time_t time1, time2;
  mju_decodeBase64((uint8_t*) &time1, timestamp);
  time2 = ((file_spec*) resource->data)->mtime;
  double diff = difftime(time2, time1);
  if (diff < 0) return -1;
  if (diff > 0) return  1;
  return 0;
 }
@@ -32,78 +32,9 @@
 #include "engine/engine_util_spatial.h"
 //-------------------------------- utility ---------------------------------------------------------
 // add sensor noise after each stage
 static void add_noise(const mjModel* m, mjData* d, mjtStage stage) {
  int adr, dim;
  mjtNum rnd[4], noise, quat[4], res[4];
  // process sensors matching stage and having positive noise
  for (int i=0; i < m->nsensor; i++) {
    if (m->sensor_needstage[i] == stage && m->sensor_noise[i] > 0) {
      // get sensor info
      adr = m->sensor_adr[i];
      dim = m->sensor_dim[i];
      noise = m->sensor_noise[i];
      // real or positive: add noise directly, with clamp for positive
      if (m->sensor_datatype[i] == mjDATATYPE_REAL ||
          m->sensor_datatype[i] == mjDATATYPE_POSITIVE) {
        for (int j=0; j < dim; j++) {
          // get random numbers; use only the first one
          rnd[0] = mju_standardNormal(rnd+1);
          // positive
          if (m->sensor_datatype[i] == mjDATATYPE_POSITIVE) {
            // add noise only if positive, keep it positive
            if (d->sensordata[adr+j] > 0) {
              d->sensordata[adr+j] = mju_max(0, d->sensordata[adr+j]+rnd[0]*noise);
            }
          }
          // real
          else {
            d->sensordata[adr+j] += rnd[0]*noise;
          }
        }
      }
      // axis or quat: rotate around random axis by random angle
      else {
        // get four random numbers
        rnd[0] = mju_standardNormal(rnd+1);
        rnd[2] = mju_standardNormal(rnd+3);
        // scale angle, normalize axis, make quaternion
        rnd[0] *= noise;
        mju_normalize3(rnd+1);
        mju_axisAngle2Quat(quat, rnd+1, rnd[0]);
        // axis
        if (m->sensor_datatype[i] == mjDATATYPE_AXIS) {
          // apply quaternion rotation to axis, assign
          mju_rotVecQuat(res, d->sensordata+adr, quat);
          mju_copy3(d->sensordata+adr, res);
        }
        // quaternion
        else if (m->sensor_datatype[i] == mjDATATYPE_QUATERNION) {
          // apply quaternion rotation to quaternion, assign
          mju_mulQuat(d->sensordata+adr, d->sensordata+adr, quat);
        }
        // unknown datatype
        else {
          mjERROR("unknown datatype in sensor %d", i);
        }
      }
    }
  }
 }
 // apply cutoff after each stage
 static void apply_cutoff(const mjModel* m, mjData* d, mjtStage stage) {
  // process sensors matching stage and having positive cutoff
@@ -442,11 +373,6 @@ void mj_sensorPos(const mjModel* m, mjData* d) {
    mjcb_sensor(m, d, mjSTAGE_POS);
  }
  // add noise if enabled
  if (mjENABLED(mjENBL_SENSORNOISE)) {
    add_noise(m, d, mjSTAGE_POS);
  }
  // compute plugin sensor values
  if (m->nplugin) {
    const int nslot = mjp_pluginCount();
@@ -623,11 +549,6 @@ void mj_sensorVel(const mjModel* m, mjData* d) {
    mjcb_sensor(m, d, mjSTAGE_VEL);
  }
  // add noise if enabled
  if (mjENABLED(mjENBL_SENSORNOISE)) {
    add_noise(m, d, mjSTAGE_VEL);
  }
  // trigger computation of plugins
  if (m->nplugin) {
    const int nslot = mjp_pluginCount();
@@ -839,11 +760,6 @@ void mj_sensorAcc(const mjModel* m, mjData* d) {
    mjcb_sensor(m, d, mjSTAGE_ACC);
  }
  // add noise if enabled
  if (mjENABLED(mjENBL_SENSORNOISE)) {
    add_noise(m, d, mjSTAGE_ACC);
  }
  // trigger computation of plugins
  if (m->nplugin) {
    const int nslot = mjp_pluginCount();
@@ -66,7 +66,6 @@ const char* mjENABLESTRING[mjNENABLE] = {
  "Override",
  "Energy",
  "Fwdinv",
  "Sensornoise",
  "InvDiscrete",
  "MultiCCD",
  "Island"
@@ -815,8 +814,8 @@ void mj_angmomMat(const mjModel* m, mjData* d, mjtNum* mat, int body) {
    // term1 = body angular momentum about self COM in world frame
    mjtNum tmp1[9], tmp2[9];
-    mju_mulMatMat(tmp1, ximat, inertia, 3, 3, 3);  // tmp1  = ximat * inertia
+    mju_mulMatMat3(tmp1, ximat, inertia);          // tmp1  = ximat * inertia
-    mju_mulMatMatT(tmp2, tmp1, ximat, 3, 3, 3);    // tmp2  = ximat * inertia * ximat^T
+    mju_mulMatMatT3(tmp2, tmp1, ximat);            // tmp2  = ximat * inertia * ximat^T
    mju_mulMatMat(term1, tmp2, jacr, 3, 3, nv);    // term1 = ximat * inertia * ximat^T * jacr
    // location of body COM w.r.t subtree COM
@@ -1050,11 +1049,11 @@ static int _getnumadr(const mjModel* m, mjtObj type, int** padr, int* mapadr) {
 }
 // get string hash, see http://www.cse.yorku.ca/~oz/hash.html
-uint64_t mj_hashdjb2(const char* s, uint64_t n) {
+uint64_t mj_hashString(const char* s, uint64_t n) {
  uint64_t h = 5381;
  int c;
  while ((c = *s++)) {
-    h  = ((h << 5) + h) + c;
+    h = ((h << 5) + h) ^ c;
  }
  return h % n;
 }
@@ -1070,7 +1069,7 @@ int mj_name2id(const mjModel* m, int type, const char* name) {
  // search
  if (num) {    // look up at hash address
-    uint64_t hash = mj_hashdjb2(name, num);
+    uint64_t hash = mj_hashString(name, num);
    uint64_t i = hash;
    do {
@@ -114,7 +114,7 @@ MJAPI void mj_angmomMat(const mjModel* m, mjData* d, mjtNum* mat, int body);
 //-------------------------- name functions --------------------------------------------------------
 // get string hash, see http://www.cse.yorku.ca/~oz/hash.html
-uint64_t mj_hashdjb2(const char* s, uint64_t n);
+uint64_t mj_hashString(const char* s, uint64_t n);
 // get id of object with the specified mjtObj type and name, returns -1 if id not found
 MJAPI int mj_name2id(const mjModel* m, int type, const char* name);
@@ -180,6 +180,51 @@ void mju_rotVecMatT(mjtNum res[3], const mjtNum vec[3], const mjtNum mat[9]) {
 // multiply 3x3 matrices,
 void mju_mulMatMat3(mjtNum res[9], const mjtNum a[9], const mjtNum b[9]) {
  res[0] = a[0]*b[0] + a[1]*b[3] + a[2]*b[6];
  res[1] = a[0]*b[1] + a[1]*b[4] + a[2]*b[7];
  res[2] = a[0]*b[2] + a[1]*b[5] + a[2]*b[8];
  res[3] = a[3]*b[0] + a[4]*b[3] + a[5]*b[6];
  res[4] = a[3]*b[1] + a[4]*b[4] + a[5]*b[7];
  res[5] = a[3]*b[2] + a[4]*b[5] + a[5]*b[8];
  res[6] = a[6]*b[0] + a[7]*b[3] + a[8]*b[6];
  res[7] = a[6]*b[1] + a[7]*b[4] + a[8]*b[7];
  res[8] = a[6]*b[2] + a[7]*b[5] + a[8]*b[8];
 }
 // multiply 3x3 matrices, first argument transposed
 void mju_mulMatTMat3(mjtNum res[9], const mjtNum a[9], const mjtNum b[9]) {
  res[0] = a[0]*b[0] + a[3]*b[3] + a[6]*b[6];
  res[1] = a[0]*b[1] + a[3]*b[4] + a[6]*b[7];
  res[2] = a[0]*b[2] + a[3]*b[5] + a[6]*b[8];
  res[3] = a[1]*b[0] + a[4]*b[3] + a[7]*b[6];
  res[4] = a[1]*b[1] + a[4]*b[4] + a[7]*b[7];
  res[5] = a[1]*b[2] + a[4]*b[5] + a[7]*b[8];
  res[6] = a[2]*b[0] + a[5]*b[3] + a[8]*b[6];
  res[7] = a[2]*b[1] + a[5]*b[4] + a[8]*b[7];
  res[8] = a[2]*b[2] + a[5]*b[5] + a[8]*b[8];
 }
 // multiply 3x3 matrices, second argument transposed
 void mju_mulMatMatT3(mjtNum res[9], const mjtNum a[9], const mjtNum b[9]) {
  res[0] = a[0]*b[0] + a[1]*b[1] + a[2]*b[2];
  res[1] = a[0]*b[3] + a[1]*b[4] + a[2]*b[5];
  res[2] = a[0]*b[6] + a[1]*b[7] + a[2]*b[8];
  res[3] = a[3]*b[0] + a[4]*b[1] + a[5]*b[2];
  res[4] = a[3]*b[3] + a[4]*b[4] + a[5]*b[5];
  res[5] = a[3]*b[6] + a[4]*b[7] + a[5]*b[8];
  res[6] = a[6]*b[0] + a[7]*b[1] + a[8]*b[2];
  res[7] = a[6]*b[3] + a[7]*b[4] + a[8]*b[5];
  res[8] = a[6]*b[6] + a[7]*b[7] + a[8]*b[8];
 }
 //------------------------------ 4D vector and matrix-vector operations ----------------------------
 // res = 0
@@ -109,6 +109,14 @@ MJAPI void mju_rotVecMat(mjtNum res[3], const mjtNum vec[3], const mjtNum mat[9]
 // multiply vector by transposed 3D rotation matrix
 MJAPI void mju_rotVecMatT(mjtNum res[3], const mjtNum vec[3], const mjtNum mat[9]);
 // multiply 3x3 matrices
 MJAPI void mju_mulMatMat3(mjtNum res[9], const mjtNum mat1[9], const mjtNum mat2[9]);
 // multiply 3x3 matrices, first argument transposed
 MJAPI void mju_mulMatTMat3(mjtNum res[9], const mjtNum a[9], const mjtNum b[9]);
 // multiply 3x3 matrices, second argument transposed
 MJAPI void mju_mulMatMatT3(mjtNum res[9], const mjtNum mat1[9], const mjtNum mat2[9]);
 //------------------------------ 4D/quaternion operations ------------------------------------------
@@ -639,7 +639,7 @@ static uint32_t _decode(char ch) {
 // returns number of chars written in buf: 4 * [(ndata + 2) / 3] + 1
 size_t mju_encodeBase64(char* buf, const uint8_t* data, size_t ndata) {
  static const char *table =
-    "ABCDEFGHIJKLMNOPQRSTUBWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
+    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
  int i = 0, j = 0;
@@ -721,8 +721,8 @@ int mju_eig3(mjtNum eigval[3], mjtNum eigvec[9], mjtNum quat[4], const mjtNum ma
  for (iter=0; iter < 500; iter++) {
    // make quaternion matrix eigvec, compute D = eigvec'*mat*eigvec
    mju_quat2Mat(eigvec, quat);
-    mju_mulMatTMat(tmp, eigvec, mat, 3, 3, 3);
+    mju_mulMatTMat3(tmp, eigvec, mat);
-    mju_mulMatMat(D, tmp, eigvec, 3, 3, 3);
+    mju_mulMatMat3(D, tmp, eigvec);
    // assign eigenvalues
    eigval[0] = D[0];
@@ -347,6 +347,29 @@ static void vfs_getdir_callback(mjResource* resource, const char** dir, int* ndi
 }
 // modified callback for the VFS resource provider
 // return > 0 if modified and 0 if unmodified
 static int vfs_modified_callback(const mjResource* resource, const char* timestamp) {
  uint64_t filestamp;
  if (mju_isValidBase64(timestamp) > sizeof(uint64_t)) {
    return 2;  // error (assume modified)
  }
  mju_decodeBase64((uint8_t*) &filestamp, timestamp);
  if (!filestamp) return 3;  // no hash (assume modified)
  if (resource) {
    const mjVFS* vfs = (const mjVFS*) resource->data;
    int i = mj_findFileVFS(vfs, resource->name);
    if (i < 0) return 4;  // missing file (assume modified)
    if (!vfs->filestamp[i]) return 5;  // missing filestamp (assume modified)
    if (vfs->filestamp[i] == filestamp) {
      return 0;  // unmodified
    }
  }
  return 1;  // modified
 }
 // open VFS resource
 mjResource* mju_openVfsResource(const char* name, const mjVFS* vfs) {
@@ -362,7 +385,7 @@ mjResource* mju_openVfsResource(const char* name, const mjVFS* vfs) {
    .read     = &vfs_read_callback,
    .close    = &vfs_close_callback,
    .getdir   = &vfs_getdir_callback,
-    .modified = NULL
+    .modified = &vfs_modified_callback,
  };
  // create resource
@@ -15,6 +15,8 @@
 set(MUJOCO_USER_SRCS
    user_api.cc
    user_api.h
    user_cache.cc
    user_cache.h
    user_composite.cc
    user_composite.h
    user_flexcomp.cc
@@ -13,80 +13,121 @@
 // limitations under the License.
 #include "user/user_api.h"
 #include <cstddef>
 #include <functional>
 #include <map>
 #include <new>
 #include <string>
 #include <string_view>
 #include <utility>
 #include <vector>
 #include <mujoco/mujoco.h>
 #include "user/user_model.h"
 #include "user/user_objects.h"
 #include "user/user_cache.h"
 #include "xml/xml_util.h"
 // prepend prefix
 template <typename T>
 static T& operator+(std::string_view prefix, T& base) {
  base.prefix = std::string(prefix);
  return base;
 }
 // append suffix
 template <typename T>
 static T& operator+(T& base, std::string_view suffix) {
  base.suffix = std::string(suffix);
  return base;
 }
 // create model
-mjSpec* mjm_createSpec() {
+mjSpec* mjs_createSpec() {
  mjCModel* modelC = new mjCModel;
  return &modelC->spec;
 }
 // copy model
 mjSpec* mjs_copySpec(const mjSpec* s) {
  mjCModel* modelC = new mjCModel(*static_cast<mjCModel*>(s->element));
  return &modelC->spec;
 }
 // copy back model
-void mjm_copyBack(mjSpec* s, const mjModel* m) {
+void mjs_copyBack(mjSpec* s, const mjModel* m) {
-  mjCModel* modelC = reinterpret_cast<mjCModel*>(s->element);
+  mjCModel* modelC = static_cast<mjCModel*>(s->element);
  modelC->CopyBack(m);
 }
 // compile model
-mjModel* mjm_compile(mjSpec* s, const mjVFS* vfs) {
+mjModel* mjs_compile(mjSpec* s, const mjVFS* vfs) {
-  mjCModel* modelC = reinterpret_cast<mjCModel*>(s->element);
+  mjCModel* modelC = static_cast<mjCModel*>(s->element);
  return modelC->Compile(vfs);
 }
 // attach body to a frame of the parent
 int mjs_attachBody(mjsFrame* parent, const mjsBody* child,
                   const char* prefix, const char* suffix) {
  mjCFrame* frame_parent = static_cast<mjCFrame*>(parent->element);
  mjCBody* child_body = static_cast<mjCBody*>(child->element);
  *frame_parent += std::string(prefix) + *child_body + std::string(suffix);
  return 0;
 }
 // get error message from model
-const char* mjm_getError(mjSpec* s) {
+const char* mjs_getError(mjSpec* s) {
-  mjCModel* modelC = reinterpret_cast<mjCModel*>(s->element);
+  mjCModel* modelC = static_cast<mjCModel*>(s->element);
  return modelC->GetError().message;
 }
 // check if model has warnings
-int mjm_isWarning(mjSpec* s) {
+int mjs_isWarning(mjSpec* s) {
-  mjCModel* modelC = reinterpret_cast<mjCModel*>(s->element);
+  mjCModel* modelC = static_cast<mjCModel*>(s->element);
  return modelC->GetError().warning;
 }
 // delete model
-void mjm_deleteSpec(mjSpec* s) {
+void mjs_deleteSpec(mjSpec* s) {
-  mjCModel* model = reinterpret_cast<mjCModel*>(s->element);
+  mjCModel* model = static_cast<mjCModel*>(s->element);
  delete model;
 }
 // add child body to body, return child spec
-mjmBody* mjm_addBody(mjmBody* bodyspec, mjmDefault* defspec) {
+mjsBody* mjs_addBody(mjsBody* bodyspec, mjsDefault* defspec) {
-  mjCDef* def = defspec ? reinterpret_cast<mjCDef*>(defspec->element) : 0;
+  mjCDef* def = defspec ? static_cast<mjCDef*>(defspec->element) : 0;
-  mjCBody* body = reinterpret_cast<mjCBody*>(bodyspec->element)->AddBody(def);
+  mjCBody* body = static_cast<mjCBody*>(bodyspec->element)->AddBody(def);
  return &body->spec;
 }
 // add site to body, return site spec
-mjmSite* mjm_addSite(mjmBody* bodyspec, mjmDefault* defspec) {
+mjsSite* mjs_addSite(mjsBody* bodyspec, mjsDefault* defspec) {
-  mjCDef* def = defspec ? reinterpret_cast<mjCDef*>(defspec->element) : 0;
+  mjCDef* def = defspec ? static_cast<mjCDef*>(defspec->element) : 0;
-  mjCBody* body = reinterpret_cast<mjCBody*>(bodyspec->element);
+  mjCBody* body = static_cast<mjCBody*>(bodyspec->element);
  mjCSite* site = body->AddSite(def);
  return &site->spec;
 }
@@ -94,9 +135,9 @@ mjmSite* mjm_addSite(mjmBody* bodyspec, mjmDefault* defspec) {
 // add joint to body
-mjmJoint* mjm_addJoint(mjmBody* bodyspec, mjmDefault* defspec) {
+mjsJoint* mjs_addJoint(mjsBody* bodyspec, mjsDefault* defspec) {
-  mjCDef* def = defspec ? reinterpret_cast<mjCDef*>(defspec->element) : 0;
+  mjCDef* def = defspec ? static_cast<mjCDef*>(defspec->element) : 0;
-  mjCBody* body = reinterpret_cast<mjCBody*>(bodyspec->element);
+  mjCBody* body = static_cast<mjCBody*>(bodyspec->element);
  mjCJoint* joint = body->AddJoint(def);
  return &joint->spec;
 }
@@ -104,8 +145,8 @@ mjmJoint* mjm_addJoint(mjmBody* bodyspec, mjmDefault* defspec) {
 // add free joint to body
-mjmJoint* mjm_addFreeJoint(mjmBody* bodyspec) {
+mjsJoint* mjs_addFreeJoint(mjsBody* bodyspec) {
-  mjCBody* body = reinterpret_cast<mjCBody*>(bodyspec->element);
+  mjCBody* body = static_cast<mjCBody*>(bodyspec->element);
  mjCJoint* joint = body->AddFreeJoint();
  return &joint->spec;
 }
@@ -113,9 +154,9 @@ mjmJoint* mjm_addFreeJoint(mjmBody* bodyspec) {
 // add geom to body
-mjmGeom* mjm_addGeom(mjmBody* bodyspec, mjmDefault* defspec) {
+mjsGeom* mjs_addGeom(mjsBody* bodyspec, mjsDefault* defspec) {
-  mjCDef* def = defspec ? reinterpret_cast<mjCDef*>(defspec->element) : 0;
+  mjCDef* def = defspec ? static_cast<mjCDef*>(defspec->element) : 0;
-  mjCBody* body = reinterpret_cast<mjCBody*>(bodyspec->element);
+  mjCBody* body = static_cast<mjCBody*>(bodyspec->element);
  mjCGeom* geom = body->AddGeom(def);
  return &geom->spec;
 }
@@ -123,9 +164,9 @@ mjmGeom* mjm_addGeom(mjmBody* bodyspec, mjmDefault* defspec) {
 // add camera to body
-mjmCamera* mjm_addCamera(mjmBody* bodyspec, mjmDefault* defspec) {
+mjsCamera* mjs_addCamera(mjsBody* bodyspec, mjsDefault* defspec) {
-  mjCDef* def = defspec ? reinterpret_cast<mjCDef*>(defspec->element) : 0;
+  mjCDef* def = defspec ? static_cast<mjCDef*>(defspec->element) : 0;
-  mjCBody* body = reinterpret_cast<mjCBody*>(bodyspec->element);
+  mjCBody* body = static_cast<mjCBody*>(bodyspec->element);
  mjCCamera* camera = body->AddCamera(def);
  return &camera->spec;
 }
@@ -133,9 +174,9 @@ mjmCamera* mjm_addCamera(mjmBody* bodyspec, mjmDefault* defspec) {
 // add light to body
-mjmLight* mjm_addLight(mjmBody* bodyspec, mjmDefault* defspec) {
+mjsLight* mjs_addLight(mjsBody* bodyspec, mjsDefault* defspec) {
-  mjCDef* def = defspec ? reinterpret_cast<mjCDef*>(defspec->element) : 0;
+  mjCDef* def = defspec ? static_cast<mjCDef*>(defspec->element) : 0;
-  mjCBody* body = reinterpret_cast<mjCBody*>(bodyspec->element);
+  mjCBody* body = static_cast<mjCBody*>(bodyspec->element);
  mjCLight* light = body->AddLight(def);
  return &light->spec;
 }
@@ -143,8 +184,8 @@ mjmLight* mjm_addLight(mjmBody* bodyspec, mjmDefault* defspec) {
 // add flex to model
-mjmFlex* mjm_addFlex(mjSpec* s) {
+mjsFlex* mjs_addFlex(mjSpec* s) {
-  mjCModel* modelC = reinterpret_cast<mjCModel*>(s->element);
+  mjCModel* modelC = static_cast<mjCModel*>(s->element);
  mjCFlex* flex = modelC->AddFlex();
  return &flex->spec;
 }
@@ -152,22 +193,23 @@ mjmFlex* mjm_addFlex(mjSpec* s) {
 // add frame to body
-mjmFrame* mjm_addFrame(mjmBody* bodyspec, mjmFrame* parentframe) {
+mjsFrame* mjs_addFrame(mjsBody* bodyspec, mjsFrame* parentframe) {
  mjCFrame* parentframeC = 0;
  if (parentframe) {
-    parentframeC = reinterpret_cast<mjCFrame*>(parentframe->element);
+    parentframeC = static_cast<mjCFrame*>(parentframe->element);
  }
-  mjCBody* body = reinterpret_cast<mjCBody*>(bodyspec->element);
+  mjCBody* body = static_cast<mjCBody*>(bodyspec->element);
  mjCFrame* frameC = body->AddFrame(parentframeC);
  frameC->SetParent(body);
  return &frameC->spec;
 }
 // add mesh to model
-mjmMesh* mjm_addMesh(mjSpec* s, mjmDefault* defspec) {
+mjsMesh* mjs_addMesh(mjSpec* s, mjsDefault* defspec) {
-  mjCDef* def = defspec ? reinterpret_cast<mjCDef*>(defspec->element) : 0;
+  mjCDef* def = defspec ? static_cast<mjCDef*>(defspec->element) : 0;
-  mjCModel* modelC = reinterpret_cast<mjCModel*>(s->element);
+  mjCModel* modelC = static_cast<mjCModel*>(s->element);
  mjCMesh* mesh = modelC->AddMesh(def);
  return &mesh->spec;
 }
@@ -175,8 +217,8 @@ mjmMesh* mjm_addMesh(mjSpec* s, mjmDefault* defspec) {
 // add height field to model
-mjmHField* mjm_addHField(mjSpec* s) {
+mjsHField* mjs_addHField(mjSpec* s) {
-  mjCModel* modelC = reinterpret_cast<mjCModel*>(s->element);
+  mjCModel* modelC = static_cast<mjCModel*>(s->element);
  mjCHField* heightField = modelC->AddHField();
  return &heightField->spec;
 }
@@ -184,8 +226,8 @@ mjmHField* mjm_addHField(mjSpec* s) {
 // add skin to model
-mjmSkin* mjm_addSkin(mjSpec* s) {
+mjsSkin* mjs_addSkin(mjSpec* s) {
-  mjCModel* modelC = reinterpret_cast<mjCModel*>(s->element);
+  mjCModel* modelC = static_cast<mjCModel*>(s->element);
  mjCSkin* skin = modelC->AddSkin();
  return &skin->spec;
 }
@@ -193,8 +235,8 @@ mjmSkin* mjm_addSkin(mjSpec* s) {
 // add texture to model
-mjmTexture* mjm_addTexture(mjSpec* s) {
+mjsTexture* mjs_addTexture(mjSpec* s) {
-  mjCModel* modelC = reinterpret_cast<mjCModel*>(s->element);
+  mjCModel* modelC = static_cast<mjCModel*>(s->element);
  mjCTexture* texture = modelC->AddTexture();
  return &texture->spec;
 }
@@ -202,9 +244,9 @@ mjmTexture* mjm_addTexture(mjSpec* s) {
 // add material to model
-mjmMaterial* mjm_addMaterial(mjSpec* s, mjmDefault* defspec) {
+mjsMaterial* mjs_addMaterial(mjSpec* s, mjsDefault* defspec) {
-  mjCModel* modelC = reinterpret_cast<mjCModel*>(s->element);
+  mjCModel* modelC = static_cast<mjCModel*>(s->element);
-  mjCDef* def = defspec ? reinterpret_cast<mjCDef*>(defspec->element) : 0;
+  mjCDef* def = defspec ? static_cast<mjCDef*>(defspec->element) : 0;
  mjCMaterial* material = modelC->AddMaterial(def);
  return &material->spec;
 }
@@ -212,9 +254,9 @@ mjmMaterial* mjm_addMaterial(mjSpec* s, mjmDefault* defspec) {
 // add pair to model
-mjmPair* mjm_addPair(mjSpec* s, mjmDefault* defspec) {
+mjsPair* mjs_addPair(mjSpec* s, mjsDefault* defspec) {
-  mjCModel* modelC = reinterpret_cast<mjCModel*>(s->element);
+  mjCModel* modelC = static_cast<mjCModel*>(s->element);
-  mjCDef* def = defspec ? reinterpret_cast<mjCDef*>(defspec->element) : 0;
+  mjCDef* def = defspec ? static_cast<mjCDef*>(defspec->element) : 0;
  mjCPair* pair = modelC->AddPair(def);
  return &pair->spec;
 }
@@ -222,8 +264,8 @@ mjmPair* mjm_addPair(mjSpec* s, mjmDefault* defspec) {
 // add pair exclusion to model
-mjmExclude* mjm_addExclude(mjSpec* s) {
+mjsExclude* mjs_addExclude(mjSpec* s) {
-  mjCModel* modelC = reinterpret_cast<mjCModel*>(s->element);
+  mjCModel* modelC = static_cast<mjCModel*>(s->element);
  mjCBodyPair* bodypair = modelC->AddExclude();
  return &bodypair->spec;
 }
@@ -231,9 +273,9 @@ mjmExclude* mjm_addExclude(mjSpec* s) {
 // add equality to model
-mjmEquality* mjm_addEquality(mjSpec* s, mjmDefault* defspec) {
+mjsEquality* mjs_addEquality(mjSpec* s, mjsDefault* defspec) {
-  mjCModel* modelC = reinterpret_cast<mjCModel*>(s->element);
+  mjCModel* modelC = static_cast<mjCModel*>(s->element);
-  mjCDef* def = defspec ? reinterpret_cast<mjCDef*>(defspec->element) : 0;
+  mjCDef* def = defspec ? static_cast<mjCDef*>(defspec->element) : 0;
  mjCEquality* equality = modelC->AddEquality(def);
  return &equality->spec;
 }
@@ -241,9 +283,9 @@ mjmEquality* mjm_addEquality(mjSpec* s, mjmDefault* defspec) {
 // add tendon to model
-mjmTendon* mjm_addTendon(mjSpec* s, mjmDefault* defspec) {
+mjsTendon* mjs_addTendon(mjSpec* s, mjsDefault* defspec) {
-  mjCModel* modelC = reinterpret_cast<mjCModel*>(s->element);
+  mjCModel* modelC = static_cast<mjCModel*>(s->element);
-  mjCDef* def = defspec ? reinterpret_cast<mjCDef*>(defspec->element) : 0;
+  mjCDef* def = defspec ? static_cast<mjCDef*>(defspec->element) : 0;
  mjCTendon* tendon = modelC->AddTendon(def);
  return &tendon->spec;
 }
@@ -251,8 +293,8 @@ mjmTendon* mjm_addTendon(mjSpec* s, mjmDefault* defspec) {
 // wrap site using tendon
-MJAPI mjmWrap* mjm_wrapSite(mjmTendon* tendonspec, const char* name) {
+MJAPI mjsWrap* mjs_wrapSite(mjsTendon* tendonspec, const char* name) {
-  mjCTendon* tendon = reinterpret_cast<mjCTendon*>(tendonspec->element);
+  mjCTendon* tendon = static_cast<mjCTendon*>(tendonspec->element);
  tendon->WrapSite(name);
  return &tendon->path.back()->spec;
 }
@@ -260,8 +302,8 @@ MJAPI mjmWrap* mjm_wrapSite(mjmTendon* tendonspec, const char* name) {
 // wrap geom using tendon
-mjmWrap* mjm_wrapGeom(mjmTendon* tendonspec, const char* name, const char* sidesite) {
+mjsWrap* mjs_wrapGeom(mjsTendon* tendonspec, const char* name, const char* sidesite) {
-  mjCTendon* tendon = reinterpret_cast<mjCTendon*>(tendonspec->element);
+  mjCTendon* tendon = static_cast<mjCTendon*>(tendonspec->element);
  tendon->WrapGeom(name, sidesite);
  return &tendon->path.back()->spec;
 }
@@ -269,8 +311,8 @@ mjmWrap* mjm_wrapGeom(mjmTendon* tendonspec, const char* name, const char* sides
 // wrap joint using tendon
-mjmWrap* mjm_wrapJoint(mjmTendon* tendonspec, const char* name, double coef) {
+mjsWrap* mjs_wrapJoint(mjsTendon* tendonspec, const char* name, double coef) {
-  mjCTendon* tendon = reinterpret_cast<mjCTendon*>(tendonspec->element);
+  mjCTendon* tendon = static_cast<mjCTendon*>(tendonspec->element);
  tendon->WrapJoint(name, coef);
  return &tendon->path.back()->spec;
 }
@@ -278,8 +320,8 @@ mjmWrap* mjm_wrapJoint(mjmTendon* tendonspec, const char* name, double coef) {
 // wrap pulley using tendon
-mjmWrap* mjm_wrapPulley(mjmTendon* tendonspec, double divisor) {
+mjsWrap* mjs_wrapPulley(mjsTendon* tendonspec, double divisor) {
-  mjCTendon* tendon = reinterpret_cast<mjCTendon*>(tendonspec->element);
+  mjCTendon* tendon = static_cast<mjCTendon*>(tendonspec->element);
  tendon->WrapPulley(divisor);
  return &tendon->path.back()->spec;
 }
@@ -287,9 +329,9 @@ mjmWrap* mjm_wrapPulley(mjmTendon* tendonspec, double divisor) {
 // add actuator to model
-mjmActuator* mjm_addActuator(mjSpec* s, mjmDefault* defspec) {
+mjsActuator* mjs_addActuator(mjSpec* s, mjsDefault* defspec) {
-  mjCModel* modelC = reinterpret_cast<mjCModel*>(s->element);
+  mjCModel* modelC = static_cast<mjCModel*>(s->element);
-  mjCDef* def = defspec ? reinterpret_cast<mjCDef*>(defspec->element) : 0;
+  mjCDef* def = defspec ? static_cast<mjCDef*>(defspec->element) : 0;
  mjCActuator* actuator = modelC->AddActuator(def);
  return &actuator->spec;
 }
@@ -297,8 +339,8 @@ mjmActuator* mjm_addActuator(mjSpec* s, mjmDefault* defspec) {
 // add sensor to model
-mjmSensor* mjm_addSensor(mjSpec* s) {
+mjsSensor* mjs_addSensor(mjSpec* s) {
-  mjCModel* modelC = reinterpret_cast<mjCModel*>(s->element);
+  mjCModel* modelC = static_cast<mjCModel*>(s->element);
  mjCSensor* sensor = modelC->AddSensor();
  return &sensor->spec;
 }
@@ -306,8 +348,8 @@ mjmSensor* mjm_addSensor(mjSpec* s) {
 // add numeric to model
-mjmNumeric* mjm_addNumeric(mjSpec* s) {
+mjsNumeric* mjs_addNumeric(mjSpec* s) {
-  mjCModel* modelC = reinterpret_cast<mjCModel*>(s->element);
+  mjCModel* modelC = static_cast<mjCModel*>(s->element);
  mjCNumeric* numeric = modelC->AddNumeric();
  return &numeric->spec;
 }
@@ -315,8 +357,8 @@ mjmNumeric* mjm_addNumeric(mjSpec* s) {
 // add text to model
-mjmText* mjm_addText(mjSpec* s) {
+mjsText* mjs_addText(mjSpec* s) {
-  mjCModel* modelC = reinterpret_cast<mjCModel*>(s->element);
+  mjCModel* modelC = static_cast<mjCModel*>(s->element);
  mjCText* text = modelC->AddText();
  return &text->spec;
 }
@@ -324,8 +366,8 @@ mjmText* mjm_addText(mjSpec* s) {
 // add tuple to model
-mjmTuple* mjm_addTuple(mjSpec* s) {
+mjsTuple* mjs_addTuple(mjSpec* s) {
-  mjCModel* modelC = reinterpret_cast<mjCModel*>(s->element);
+  mjCModel* modelC = static_cast<mjCModel*>(s->element);
  mjCTuple* tuple = modelC->AddTuple();
  return &tuple->spec;
 }
@@ -333,8 +375,8 @@ mjmTuple* mjm_addTuple(mjSpec* s) {
 // add keyframe to model
-mjmKey* mjm_addKey(mjSpec* s) {
+mjsKey* mjs_addKey(mjSpec* s) {
-  mjCModel* modelC = reinterpret_cast<mjCModel*>(s->element);
+  mjCModel* modelC = static_cast<mjCModel*>(s->element);
  mjCKey* key = modelC->AddKey();
  return &key->spec;
 }
@@ -342,18 +384,18 @@ mjmKey* mjm_addKey(mjSpec* s) {
 // add plugin to model
-mjmPlugin* mjm_addPlugin(mjSpec* s) {
+mjsPlugin* mjs_addPlugin(mjSpec* s) {
-  mjCModel* modelC = reinterpret_cast<mjCModel*>(s->element);
+  mjCModel* modelC = static_cast<mjCModel*>(s->element);
  mjCPlugin* plugin = modelC->AddPlugin();
-  plugin->spec.instance = (mjElement)plugin;
+  plugin->spec.instance = static_cast<mjElement*>(plugin);
  return &plugin->spec;
 }
 // add default to model
-mjmDefault* mjm_addDefault(mjSpec* s, const char* classname, int parentid, int* id) {
+mjsDefault* mjs_addDefault(mjSpec* s, const char* classname, int parentid, int* id) {
-  mjCModel* modelC = reinterpret_cast<mjCModel*>(s->element);
+  mjCModel* modelC = static_cast<mjCModel*>(s->element);
  *id = (int)modelC->defaults.size();
  mjCDef* def = modelC->AddDef(classname, parentid);
  if (def) {
@@ -366,22 +408,22 @@ mjmDefault* mjm_addDefault(mjSpec* s, const char* classname, int parentid, int*
 // get objects
-mjSpec* mjm_getSpec(mjmBody* body) {
+mjSpec* mjs_getSpec(mjsBody* body) {
-  return &(reinterpret_cast<mjCBody*>(body->element)->model->spec);
+  return &(static_cast<mjCBody*>(body->element)->model->spec);
 }
 // get default
-mjmDefault* mjm_getDefault(mjElement element) {
+mjsDefault* mjs_getDefault(mjElement* element) {
-  return &(reinterpret_cast<mjCBase*>(element)->def->spec);
+  return &(static_cast<mjCBase*>(element)->def->spec);
 }
 // Find default with given name in model.
-mjmDefault* mjm_findDefault(mjSpec* s, const char* classname) {
+mjsDefault* mjs_findDefault(mjSpec* s, const char* classname) {
-  mjCModel* modelC = reinterpret_cast<mjCModel*>(s->element);
+  mjCModel* modelC = static_cast<mjCModel*>(s->element);
  mjCDef* cdef = modelC->FindDef(classname);
  if (!cdef) {
    return nullptr;
@@ -392,8 +434,8 @@ mjmDefault* mjm_findDefault(mjSpec* s, const char* classname) {
 // get default[0] from model
-mjmDefault* mjm_getSpecDefault(mjSpec* s) {
+mjsDefault* mjs_getSpecDefault(mjSpec* s) {
-  mjCModel* modelC = reinterpret_cast<mjCModel*>(s->element);
+  mjCModel* modelC = static_cast<mjCModel*>(s->element);
  mjCDef* def = modelC->defaults[0];
  if (!def) {
    return nullptr;
@@ -404,70 +446,83 @@ mjmDefault* mjm_getSpecDefault(mjSpec* s) {
 // find body in model by name
-mjmBody* mjm_findBody(mjSpec* s, const char* name) {
+mjsBody* mjs_findBody(mjSpec* s, const char* name) {
-  mjCModel* model = reinterpret_cast<mjCModel*>(s->element);
+  mjCModel* model = static_cast<mjCModel*>(s->element);
-  mjCBase* body = model->FindObject(mjOBJ_BODY, std::string(name));
+  mjCBase* body = 0;
-  if (!body) {
+  if (model->IsCompiled()) {
-    return 0;
+    body = model->FindObject(mjOBJ_BODY, std::string(name));  // fast lookup
  } else {
    body = model->FindBody(model->GetWorld(), std::string(name));  // recursive search
  }
-  return &(static_cast<mjCBody*>(body)->spec);
+  return body ? &(static_cast<mjCBody*>(body)->spec) : nullptr;
 }
 // find child of a body by name
-mjmBody* mjm_findChild(mjmBody* bodyspec, const char* name) {
+mjsBody* mjs_findChild(mjsBody* bodyspec, const char* name) {
-  mjCBody* body = reinterpret_cast<mjCBody*>(bodyspec->element);
+  mjCBody* body = static_cast<mjCBody*>(bodyspec->element);
  mjCBase* child = body->FindObject(mjOBJ_BODY, std::string(name));
-  if (!child) {
+  return child ? &(static_cast<mjCBody*>(child)->spec) : nullptr;
    return 0;
  }
  return &(static_cast<mjCBody*>(child)->spec);
 }
 // find mesh by name
-mjmMesh* mjm_findMesh(mjSpec* s, const char* name) {
+mjsMesh* mjs_findMesh(mjSpec* s, const char* name) {
-  mjCModel* model = reinterpret_cast<mjCModel*>(s->element);
+  mjCModel* model = static_cast<mjCModel*>(s->element);
  mjCMesh* mesh = (mjCMesh*)model->FindObject(mjOBJ_MESH, std::string(name));
-  if (!mesh) {
+  return mesh ? &(static_cast<mjCMesh*>(mesh)->spec) : nullptr;
-    return nullptr;
+}
-  }
+
-  return &(static_cast<mjCMesh*>(mesh)->spec);
+
 // find frame by name
 mjsFrame* mjs_findFrame(mjSpec* s, const char* name) {
  mjCModel* model = static_cast<mjCModel*>(s->element);
  mjCFrame* frame = (mjCFrame*)model->FindFrame(model->GetWorld(), std::string(name));
  return frame ? &(static_cast<mjCFrame*>(frame)->spec) : nullptr;
 }
 // set frame
-void mjm_setFrame(mjElement dest, mjmFrame* frame) {
+void mjs_setFrame(mjElement* dest, mjsFrame* frame) {
  if (!frame) {
    return;
  }
-  mjCFrame* frameC = reinterpret_cast<mjCFrame*>(frame->element);
+  mjCFrame* frameC = static_cast<mjCFrame*>(frame->element);
-  mjCBase* baseC = reinterpret_cast<mjCBase*>(dest);
+  mjCBase* baseC = static_cast<mjCBase*>(dest);
  baseC->SetFrame(frameC);
 }
 // Resolve alternative orientations.
 const char* mjs_resolveOrientation(double quat[4], mjtByte degree, const char* sequence,
                                   const mjsOrientation* orientation) {
  return ResolveOrientation(quat, degree, sequence, *orientation);
 }
 // get id
-int mjm_getId(mjElement element) {
+int mjs_getId(mjElement* element) {
-  return reinterpret_cast<mjCBase*>(element)->id;
+  return static_cast<mjCBase*>(element)->id;
 }
 // set default
-void mjm_setDefault(mjElement element, mjmDefault* defspec) {
+void mjs_setDefault(mjElement* element, mjsDefault* defspec) {
-  mjCBase* baseC = reinterpret_cast<mjCBase*>(element);
+  mjCBase* baseC = static_cast<mjCBase*>(element);
-  baseC->def = reinterpret_cast<mjCDef*>(defspec->element);
+  baseC->def = static_cast<mjCDef*>(defspec->element);
 }
 // set string
-void mjm_setString(mjString dest, const char* text) {
+void mjs_setString(mjString dest, const char* text) {
  std::string* str = reinterpret_cast<std::string*>(dest);
  *str = std::string(text);
 }
@@ -475,10 +530,10 @@ void mjm_setString(mjString dest, const char* text) {
 // Set specific entry in destination string vector.
-mjtByte mjm_setInStringVec(mjStringVec dest, int i, const char* text) {
+mjtByte mjs_setInStringVec(mjStringVec dest, int i, const char* text) {
  std::vector<std::string>* v = reinterpret_cast<std::vector<std::string>*>(dest);
  if (v->size() <= i) {
-    mju_error("Requested index in mjm_setInStringVec is out of bounds");
+    mju_error("Requested index in mjs_setInStringVec is out of bounds");
    return 0;
  }
  v->at(i) = std::string(text);
@@ -488,7 +543,7 @@ mjtByte mjm_setInStringVec(mjStringVec dest, int i, const char* text) {
 // split text and copy into string array
-void mjm_setStringVec(mjStringVec dest, const char* text) {
+void mjs_setStringVec(mjStringVec dest, const char* text) {
  std::vector<std::string>* v = reinterpret_cast<std::vector<std::string>*>(dest);
  *v = mjXUtil::String2Vector<std::string>(text);
 }
@@ -496,14 +551,14 @@ void mjm_setStringVec(mjStringVec dest, const char* text) {
 // add text entry to destination string vector
-void mjm_appendString(mjStringVec dest, const char* text) {
+void mjs_appendString(mjStringVec dest, const char* text) {
  std::vector<std::string>* v = reinterpret_cast<std::vector<std::string>*>(dest);
  v->push_back(std::string(text));
 }
 // copy int array to vector
-void mjm_setInt(mjIntVec dest, const int* array, int size) {
+void mjs_setInt(mjIntVec dest, const int* array, int size) {
  std::vector<int>* v = reinterpret_cast<std::vector<int>*>(dest);
  v->assign(size, 0.0);
  for (int i = 0; i < size; ++i) {
@@ -514,7 +569,7 @@ void mjm_setInt(mjIntVec dest, const int* array, int size) {
 // append int array to vector of arrays
-void mjm_appendIntVec(mjIntVecVec dest, const int* array, int size) {
+void mjs_appendIntVec(mjIntVecVec dest, const int* array, int size) {
  std::vector<std::vector<int>>* v = reinterpret_cast<std::vector<std::vector<int>>*>(dest);
  v->push_back(std::vector<int>(array, array + size));
 }
@@ -522,7 +577,7 @@ void mjm_appendIntVec(mjIntVecVec dest, const int* array, int size) {
 // copy float array to vector
-void mjm_setFloat(mjFloatVec dest, const float* array, int size) {
+void mjs_setFloat(mjFloatVec dest, const float* array, int size) {
  std::vector<float>* v = reinterpret_cast<std::vector<float>*>(dest);
  v->assign(size, 0.0);
  for (int i = 0; i < size; ++i) {
@@ -534,7 +589,7 @@ void mjm_setFloat(mjFloatVec dest, const float* array, int size) {
 // append float array to vector of arrays
-void mjm_appendFloatVec(mjFloatVecVec dest, const float* array, int size) {
+void mjs_appendFloatVec(mjFloatVecVec dest, const float* array, int size) {
  std::vector<std::vector<float>>* v = reinterpret_cast<std::vector<std::vector<float>>*>(dest);
  v->push_back(std::vector<float>(array, array + size));
 }
@@ -542,7 +597,7 @@ void mjm_appendFloatVec(mjFloatVecVec dest, const float* array, int size) {
 // copy double array to vector
-void mjm_setDouble(mjDoubleVec dest, const double* array, int size) {
+void mjs_setDouble(mjDoubleVec dest, const double* array, int size) {
  std::vector<double>* v = reinterpret_cast<std::vector<double>*>(dest);
  v->assign(size, 0.0);
  for (int i = 0; i < size; ++i) {
@@ -553,7 +608,7 @@ void mjm_setDouble(mjDoubleVec dest, const double* array, int size) {
 // get string
-const char* mjm_getString(const mjString source) {
+const char* mjs_getString(const mjString source) {
  std::string* str = reinterpret_cast<std::string*>(source);
  if (!str) {
    return nullptr;
@@ -564,7 +619,7 @@ const char* mjm_getString(const mjString source) {
 // get double array
-const double* mjm_getDouble(const mjDoubleVec source, int* size) {
+const double* mjs_getDouble(const mjDoubleVec source, int* size) {
  std::vector<double>* v = reinterpret_cast<std::vector<double>*>(source);
  if (size) {
    *size = v->size();
@@ -575,8 +630,8 @@ const double* mjm_getDouble(const mjDoubleVec source, int* size) {
 // set plugin attributes
-void mjm_setPluginAttributes(mjmPlugin* plugin, void* attributes) {
+void mjs_setPluginAttributes(mjsPlugin* plugin, void* attributes) {
-  mjCPlugin* pluginC = reinterpret_cast<mjCPlugin*>(plugin->instance);
+  mjCPlugin* pluginC = static_cast<mjCPlugin*>(plugin->instance);
  std::map<std::string, std::string, std::less<>>* config_attribs =
      reinterpret_cast<std::map<std::string, std::string, std::less<>>*>(attributes);
  pluginC->config_attribs = std::move(*config_attribs);
@@ -585,8 +640,8 @@ void mjm_setPluginAttributes(mjmPlugin* plugin, void* attributes) {
 // Set active plugins.
-void mjm_setActivePlugins(mjSpec* s, void* activeplugins) {
+void mjs_setActivePlugins(mjSpec* s, void* activeplugins) {
-  mjCModel* modelC = reinterpret_cast<mjCModel*>(s->element);
+  mjCModel* modelC = static_cast<mjCModel*>(s->element);
  std::vector<std::pair<const mjpPlugin*, int>>* active_plugins =
      reinterpret_cast<std::vector<std::pair<const mjpPlugin*, int>>*>(activeplugins);
  modelC->active_plugins = std::move(*active_plugins);
@@ -595,9 +650,22 @@ void mjm_setActivePlugins(mjSpec* s, void* activeplugins) {
 // compute full inertia
-const char* mjm_setFullInertia(mjmBody* bodyspec, double quat[4], double inertia[3]) {
+const char* mjs_setFullInertia(mjsBody* bodyspec, double quat[4], double inertia[3]) {
-  mjCBody* body = reinterpret_cast<mjCBody*>(bodyspec->element);
+  mjCBody* body = static_cast<mjCBody*>(bodyspec->element);
  return body->FullInertia(quat, inertia);
 }
 // -------------------------- GLOBAL ASSET CACHE -------------------------------
 void mj_setCacheSize(mjCache cache, std::size_t size) {
  mjCCache* ccache = reinterpret_cast<mjCCache*>(cache);
  if (ccache) {
    ccache->SetMaxSize(size);
  }
 }
 mjCache mj_globalCache() {
  return NULL;  // currently disabled
 }
@@ -29,7 +29,6 @@ extern "C" {
 //---------------------------------- handles to internal objects -----------------------------------
 typedef struct _mjElement* mjElement;
 typedef struct _mjString* mjString;
 typedef struct _mjStringVec* mjStringVec;
 typedef struct _mjIntVec* mjIntVec;
@@ -77,10 +76,15 @@ typedef enum _mjtInertiaFromGeom {
 } mjtInertiaFromGeom;
-//---------------------------------- attribute structs (mjm) ---------------------------------------
+//---------------------------------- attribute structs (mjs) ---------------------------------------
 typedef struct _mjElement {        // element type, do not modify
  mjtObj elemtype;                 // element type
 } mjElement;
 typedef struct _mjSpec {           // model specification
-  mjElement element;               // internal, do not modify
+  mjElement* element;              // object type
  mjStatistic stat;                // statistics override (if defined)
  // compiler settings
@@ -135,40 +139,40 @@ typedef struct _mjSpec {           // model specification
 } mjSpec;
-typedef struct _mjmOrientation {   // alternative orientation specifiers
+typedef struct _mjsOrientation {   // alternative orientation specifiers
  double axisangle[4];             // rotation axis and angle
  double xyaxes[6];                // x and y axes
  double zaxis[3];                 // z axis (use minimal rotation)
  double euler[3];                 // euler angles
-} mjmOrientation;
+} mjsOrientation;
-typedef struct _mjmPlugin {        // plugin specification
+typedef struct _mjsPlugin {        // plugin specification
-  mjElement instance;              // internal, do not modify
+  mjElement* instance;             // object type
  mjString name;                   // name
  mjString instance_name;          // instance name
  int plugin_slot;                 // global registered slot number of the plugin
  mjtByte active;                  // is the plugin active
  mjString info;                   // message appended to compiler errors
-} mjmPlugin;
+} mjsPlugin;
-typedef struct _mjmBody {          // body specification
+typedef struct _mjsBody {          // body specification
-  mjElement element;               // internal, do not modify
+  mjElement* element;              // object type
  mjString name;                   // name
  mjString childclass;             // childclass name
  // body frame
  double pos[3];                   // frame position
  double quat[4];                  // frame orientation
-  mjmOrientation alt;              // frame alternative orientation
+  mjsOrientation alt;              // frame alternative orientation
  // inertial frame
  double mass;                     // mass
  double ipos[3];                  // inertial frame position
  double iquat[4];                 // inertial frame orientation
  double inertia[3];               // diagonal inertia (in i-frame)
-  mjmOrientation ialt;             // inertial frame alternative orientation
+  mjsOrientation ialt;             // inertial frame alternative orientation
  double fullinertia[6];           // non-axis-aligned inertia matrix
  // other
@@ -176,24 +180,24 @@ typedef struct _mjmBody {          // body specification
  double gravcomp;                 // gravity compensation
  mjDoubleVec userdata;            // user data
  mjtByte explicitinertial;        // whether to save the body with explicit inertial clause
-  mjmPlugin plugin;                // passive force plugin
+  mjsPlugin plugin;                // passive force plugin
  mjString info;                   // message appended to compiler errors
-} mjmBody;
+} mjsBody;
-typedef struct _mjmFrame {         // frame specification
+typedef struct _mjsFrame {         // frame specification
-  mjElement element;               // internal, do not modify
+  mjElement* element;              // object type
  mjString name;                   // name
  mjString childclass;             // childclass name
  double pos[3];                   // position
  double quat[4];                  // orientation
-  mjmOrientation alt;              // alternative orientation
+  mjsOrientation alt;              // alternative orientation
  mjString info;                   // message appended to compiler errors
-} mjmFrame;
+} mjsFrame;
-typedef struct _mjmJoint {         // joint specification
+typedef struct _mjsJoint {         // joint specification
-  mjElement element;               // internal, do not modify
+  mjElement* element;              // object type
  mjString name;                   // name
  mjString classname;              // class name
  mjtJoint type;                   // joint type
@@ -226,14 +230,15 @@ typedef struct _mjmJoint {         // joint specification
  // other
  int group;                       // group
  mjtByte actgravcomp;             // is gravcomp force applied via actuators
  double urdfeffort;               // effort (urdf)
  mjDoubleVec userdata;            // user data
  mjString info;                   // message appended to compiler errors
-} mjmJoint;
+} mjsJoint;
-typedef struct _mjmGeom {          // geom specification
+typedef struct _mjsGeom {          // geom specification
-  mjElement element;               // internal, do not modify
+  mjElement* element;              // object type
  mjString name;                   // name
  mjString classname;              // classname
  mjtGeom type;                    // geom type
@@ -241,7 +246,7 @@ typedef struct _mjmGeom {          // geom specification
  // frame, size
  double pos[3];                   // position
  double quat[4];                  // orientation
-  mjmOrientation alt;              // alternative orientation
+  mjsOrientation alt;              // alternative orientation
  double fromto[6];                // alternative for capsule, cylinder, box, ellipsoid
  double size[3];                  // type-specific size
@@ -276,20 +281,20 @@ typedef struct _mjmGeom {          // geom specification
  mjString meshname;               // mesh attached to geom
  double fitscale;                 // scale mesh uniformly
  mjDoubleVec userdata;            // user data
-  mjmPlugin plugin;                // sdf plugin
+  mjsPlugin plugin;                // sdf plugin
  mjString info;                   // message appended to compiler errors
-} mjmGeom;
+} mjsGeom;
-typedef struct _mjmSite {          // site specification
+typedef struct _mjsSite {          // site specification
-  mjElement element;               // internal, do not modify
+  mjElement* element;              // object type
  mjString name;                   // name
  mjString classname;              // class name
  // frame, size
  double pos[3];                   // position
  double quat[4];                  // orientation
-  mjmOrientation alt;              // alternative orientation
+  mjsOrientation alt;              // alternative orientation
  double fromto[6];                // alternative for capsule, cylinder, box, ellipsoid
  double size[3];                  // geom size
@@ -302,18 +307,18 @@ typedef struct _mjmSite {          // site specification
  // other
  mjDoubleVec userdata;            // user data
  mjString info;                   // message appended to compiler errors
-} mjmSite;
+} mjsSite;
-typedef struct _mjmCamera {        // camera specification
+typedef struct _mjsCamera {        // camera specification
-  mjElement element;               // internal, do not modify
+  mjElement* element;              // object type
  mjString name;                   // name
  mjString classname;              // class name
  // extrinsics
  double pos[3];                   // position
  double quat[4];                  // orientation
-  mjmOrientation alt;              // alternative orientation
+  mjsOrientation alt;              // alternative orientation
  mjtCamLight mode;                // tracking mode
  mjString targetbody;             // target body for tracking/targeting
@@ -331,11 +336,11 @@ typedef struct _mjmCamera {        // camera specification
  // other
  mjDoubleVec userdata;            // user data
  mjString info;                   // message appended to compiler errors
-} mjmCamera;
+} mjsCamera;
-typedef struct _mjmLight {         // light specification
+typedef struct _mjsLight {         // light specification
-  mjElement element;               // internal, do not modify
+  mjElement* element;              // object type
  mjString name;                   // name
  mjString classname;              // class name
@@ -358,11 +363,11 @@ typedef struct _mjmLight {         // light specification
  // other
  mjString info;                   // message appended to compiler errors
-} mjmLight;
+} mjsLight;
-typedef struct _mjmFlex {
+typedef struct _mjsFlex {
-  mjElement element;               // internal, do not modify
+  mjElement* element;              // object type
  mjString name;                   // name
  mjString classname;              // class name
@@ -399,11 +404,11 @@ typedef struct _mjmFlex {
  // other
  mjString info;                   // message appended to compiler errors
-} mjmFlex;
+} mjsFlex;
-typedef struct _mjmMesh {          // mesh specification
+typedef struct _mjsMesh {          // mesh specification
-  mjElement element;               // internal, do not modify
+  mjElement* element;              // object type
  mjString name;                   // name
  mjString classname;              // class name
  mjString content_type;           // content type of file
@@ -418,13 +423,13 @@ typedef struct _mjmMesh {          // mesh specification
  mjIntVec userface;               // user vertex indices
  mjIntVec userfacenormal;         // user normal indices
  mjIntVec userfacetexcoord;       // user texcoord indices
-  mjmPlugin plugin;                // sdf plugin
+  mjsPlugin plugin;                // sdf plugin
  mjString info;                   // message appended to compiler errors
-} mjmMesh;
+} mjsMesh;
-typedef struct _mjmHField {        // height field specification
+typedef struct _mjsHField {        // height field specification
-  mjElement element;               // internal, do not modify
+  mjElement* element;              // object type
  mjString name;                   // name
  mjString content_type;           // content type of file
  mjString file;                   // file: (nrow, ncol, [elevation data])
@@ -433,12 +438,12 @@ typedef struct _mjmHField {        // height field specification
  int ncol;                        // number of columns
  mjFloatVec userdata;             // user-provided elevation data
  mjString info;                   // message appended to compiler errors
-} mjmHField;
+} mjsHField;
-typedef struct _mjmSkin {          // skin specification
+typedef struct _mjsSkin {          // skin specification
-  mjElement element;               // internal, do not modify
+  mjElement* element;              // object type
  mjString name;                   // name
  mjString classname;              // class name
  mjString file;                   // skin file
@@ -461,11 +466,11 @@ typedef struct _mjmSkin {          // skin specification
  // other
  mjString info;                   // message appended to compiler errors
-} mjmSkin;
+} mjsSkin;
-typedef struct _mjmTexture {       // texture specification
+typedef struct _mjsTexture {       // texture specification
-  mjElement element;               // internal, do not modify
+  mjElement* element;              // object type
  mjString name;                   // name
  mjString classname;              // class name
  mjtTexture type;                 // texture type
@@ -495,11 +500,11 @@ typedef struct _mjmTexture {       // texture specification
  // other
  mjString info;                   // message appended to compiler errors
-} mjmTexture;
+} mjsTexture;
-typedef struct _mjmMaterial {      // material specification
+typedef struct _mjsMaterial {      // material specification
-  mjElement element;               // internal, do not modify
+  mjElement* element;              // object type
  mjString name;                   // name
  mjString classname;              // class name
  mjString texture;                // name of texture (empty: none)
@@ -511,11 +516,11 @@ typedef struct _mjmMaterial {      // material specification
  float reflectance;               // reflectance
  float rgba[4];                   // rgba
  mjString info;                   // message appended to compiler errors
-} mjmMaterial;
+} mjsMaterial;
-typedef struct _mjmPair {
+typedef struct _mjsPair {
-  mjElement element;               // internal, do not modify
+  mjElement* element;              // object type
  mjString name;                   // name
  mjString classname;              // class name
  mjString geomname1;              // name of geom 1
@@ -530,20 +535,20 @@ typedef struct _mjmPair {
  double gap;                      // include in solver if dist<margin-gap
  double friction[5];              // full contact friction
  mjString info;                   // message appended to errors
-} mjmPair;
+} mjsPair;
-typedef struct _mjmExclude {
+typedef struct _mjsExclude {
-  mjElement element;               // internal, do not modify
+  mjElement* element;              // object type
  mjString name;                   // name
  mjString bodyname1;              // name of geom 1
  mjString bodyname2;              // name of geom 2
  mjString info;                   // message appended to errors
-} mjmExclude;
+} mjsExclude;
-typedef struct _mjmEquality {      // equality specification
+typedef struct _mjsEquality {      // equality specification
-  mjElement element;               // internal, do not modify
+  mjElement* element;              // object type
  mjString name;                   // name
  mjString classname;              // class name
  mjtEq type;                      // constraint type
@@ -554,11 +559,11 @@ typedef struct _mjmEquality {      // equality specification
  mjtNum solref[mjNREF];           // solver reference
  mjtNum solimp[mjNIMP];           // solver impedance
  mjString info;                   // message appended to errors
-} mjmEquality;
+} mjsEquality;
-typedef struct _mjmTendon {        // tendon specification
+typedef struct _mjsTendon {        // tendon specification
-  mjElement element;               // internal, do not modify
+  mjElement* element;              // object type
  mjString name;                   // name
  mjString classname;              // class name
@@ -586,17 +591,17 @@ typedef struct _mjmTendon {        // tendon specification
  // other
  mjDoubleVec userdata;            // user data
  mjString info;                   // message appended to errors
-} mjmTendon;
+} mjsTendon;
-typedef struct _mjmWrap {          // wrapping object specification
+typedef struct _mjsWrap {          // wrapping object specification
-  mjElement element;               // internal, do not modify
+  mjElement* element;              // object type
  mjString info;                   // message appended to errors
-} mjmWrap;
+} mjsWrap;
-typedef struct _mjmActuator {      // actuator specification
+typedef struct _mjsActuator {      // actuator specification
-  mjElement element;               // internal, do not modify
+  mjElement* element;              // object type
  mjString name;                   // name
  mjString classname;              // class name
@@ -634,13 +639,13 @@ typedef struct _mjmActuator {      // actuator specification
  // other
  int group;                       // group
  mjDoubleVec userdata;            // user data
-  mjmPlugin plugin;                // actuator plugin
+  mjsPlugin plugin;                // actuator plugin
  mjString info;                   // message appended to compiler errors
-} mjmActuator;
+} mjsActuator;
-typedef struct _mjmSensor {        // sensor specfication
+typedef struct _mjsSensor {        // sensor specification
-  mjElement element;               // internal, do not modify
+  mjElement* element;              // object type
  mjString name;                   // name
  mjString classname;              // class name
@@ -662,40 +667,40 @@ typedef struct _mjmSensor {        // sensor specfication
  // other
  mjDoubleVec userdata;            // user data
-  mjmPlugin plugin;                // sensor plugin
+  mjsPlugin plugin;                // sensor plugin
  mjString info;                   // message appended to compiler errors
-} mjmSensor;
+} mjsSensor;
-typedef struct _mjmNumeric {       // custom numeric field specification
+typedef struct _mjsNumeric {       // custom numeric field specification
-  mjElement element;               // internal, do not modify
+  mjElement* element;              // object type
  mjString name;                   // name
  mjDoubleVec data;                // initialization data
  int size;                        // array size, can be bigger than data size
  mjString info;                   // message appended to compiler errors
-} mjmNumeric;
+} mjsNumeric;
-typedef struct _mjmText {          // custom text specification
+typedef struct _mjsText {          // custom text specification
-  mjElement element;               // internal, do not modify
+  mjElement* element;              // object type
  mjString name;                   // name
  mjString data;                   // text string
  mjString info;                   // message appended to compiler errors
-} mjmText;
+} mjsText;
-typedef struct _mjmTuple {         // tuple specification
+typedef struct _mjsTuple {         // tuple specification
-  mjElement element;               // internal, do not modify
+  mjElement* element;              // object type
  mjString name;                   // name
  mjIntVec objtype;                // object types
  mjStringVec objname;             // object names
  mjDoubleVec objprm;              // object parameters
  mjString info;                   // message appended to compiler errors
-} mjmTuple;
+} mjsTuple;
-typedef struct _mjmKey {           // keyframe specification
+typedef struct _mjsKey {           // keyframe specification
-  mjElement element;               // internal, do not modify
+  mjElement* element;              // object type
  mjString name;                   // name
  double time;                     // time
  mjDoubleVec qpos;                // qpos
@@ -705,283 +710,310 @@ typedef struct _mjmKey {           // keyframe specification
  mjDoubleVec mquat;               // mocap quat
  mjDoubleVec ctrl;                // ctrl
  mjString info;                   // message appended to compiler errors
-} mjmKey;
+} mjsKey;
-typedef struct _mjmDefault {       // default specification
+typedef struct _mjsDefault {       // default specification
  mjString name;                   // name
-  mjElement element;               // internal, do not modify
+  mjElement* element;              // object type
-  mjmJoint* joint;                 // joint defaults
+  mjsJoint* joint;                 // joint defaults
-  mjmGeom* geom;                   // geom defaults
+  mjsGeom* geom;                   // geom defaults
-  mjmSite* site;                   // site defaults
+  mjsSite* site;                   // site defaults
-  mjmCamera* camera;               // camera defaults
+  mjsCamera* camera;               // camera defaults
-  mjmLight* light;                 // light defaults
+  mjsLight* light;                 // light defaults
-  mjmFlex* flex;                   // flex defaults
+  mjsFlex* flex;                   // flex defaults
-  mjmMesh* mesh;                   // mesh defaults
+  mjsMesh* mesh;                   // mesh defaults
-  mjmMaterial* material;           // material defaults
+  mjsMaterial* material;           // material defaults
-  mjmPair* pair;                   // pair defaults
+  mjsPair* pair;                   // pair defaults
-  mjmEquality* equality;           // equality defaults
+  mjsEquality* equality;           // equality defaults
-  mjmTendon* tendon;               // tendon defaults
+  mjsTendon* tendon;               // tendon defaults
-  mjmActuator* actuator;           // actuator defaults
+  mjsActuator* actuator;           // actuator defaults
-} mjmDefault;
+} mjsDefault;
 //---------------------------------- API functions -------------------------------------------------
 // Create model.
-MJAPI mjSpec* mjm_createSpec();
+MJAPI mjSpec* mjs_createSpec();
 // Copy model.
 MJAPI mjSpec* mjs_copySpec(const mjSpec* s);
 // Copy back model.
-MJAPI void mjm_copyBack(mjSpec* s, const mjModel* m);
+MJAPI void mjs_copyBack(mjSpec* s, const mjModel* m);
 // Compile model.
-MJAPI mjModel* mjm_compile(mjSpec* s, const mjVFS* vfs);
+MJAPI mjModel* mjs_compile(mjSpec* s, const mjVFS* vfs);
 // Attach child body to a frame of the parent, return 0 if success
 MJAPI int mjs_attachBody(mjsFrame* parent, const mjsBody* child,
                         const char* prefix, const char* suffix);
 // Get error message from model.
-MJAPI const char* mjm_getError(mjSpec* s);
+MJAPI const char* mjs_getError(mjSpec* s);
 // Return 1 if model has warnings.
-MJAPI int mjm_isWarning(mjSpec* s);
+MJAPI int mjs_isWarning(mjSpec* s);
 // Delete model.
-MJAPI void mjm_deleteSpec(mjSpec* s);
+MJAPI void mjs_deleteSpec(mjSpec* s);
 // Add child body to body, return child spec.
-MJAPI mjmBody* mjm_addBody(mjmBody* body, mjmDefault* def);
+MJAPI mjsBody* mjs_addBody(mjsBody* body, mjsDefault* def);
 // Add site to body, return site spec.
-MJAPI mjmSite* mjm_addSite(mjmBody* body, mjmDefault* def);
+MJAPI mjsSite* mjs_addSite(mjsBody* body, mjsDefault* def);
 // Add joint to body.
-MJAPI mjmJoint* mjm_addJoint(mjmBody* body, mjmDefault* def);
+MJAPI mjsJoint* mjs_addJoint(mjsBody* body, mjsDefault* def);
 // Add freejoint to body.
-MJAPI mjmJoint* mjm_addFreeJoint(mjmBody* body);
+MJAPI mjsJoint* mjs_addFreeJoint(mjsBody* body);
 // Add geom to body.
-MJAPI mjmGeom* mjm_addGeom(mjmBody* body, mjmDefault* def);
+MJAPI mjsGeom* mjs_addGeom(mjsBody* body, mjsDefault* def);
 // Add camera to body.
-MJAPI mjmCamera* mjm_addCamera(mjmBody* body, mjmDefault* def);
+MJAPI mjsCamera* mjs_addCamera(mjsBody* body, mjsDefault* def);
 // Add light to body.
-MJAPI mjmLight* mjm_addLight(mjmBody* body, mjmDefault* def);
+MJAPI mjsLight* mjs_addLight(mjsBody* body, mjsDefault* def);
 // Add frame to body.
-MJAPI mjmFrame* mjm_addFrame(mjmBody* body, mjmFrame* parentframe);
+MJAPI mjsFrame* mjs_addFrame(mjsBody* body, mjsFrame* parentframe);
 // Add flex to model.
-MJAPI mjmFlex* mjm_addFlex(mjSpec* s);
+MJAPI mjsFlex* mjs_addFlex(mjSpec* s);
 // Add mesh to model.
-MJAPI mjmMesh* mjm_addMesh(mjSpec* s, mjmDefault* def);
+MJAPI mjsMesh* mjs_addMesh(mjSpec* s, mjsDefault* def);
 // Add height field to model.
-MJAPI mjmHField* mjm_addHField(mjSpec* s);
+MJAPI mjsHField* mjs_addHField(mjSpec* s);
 // Add skin to model.
-MJAPI mjmSkin* mjm_addSkin(mjSpec* s);
+MJAPI mjsSkin* mjs_addSkin(mjSpec* s);
 // Add texture to model.
-MJAPI mjmTexture* mjm_addTexture(mjSpec* s);
+MJAPI mjsTexture* mjs_addTexture(mjSpec* s);
 // Add material to model.
-MJAPI mjmMaterial* mjm_addMaterial(mjSpec* s, mjmDefault* def);
+MJAPI mjsMaterial* mjs_addMaterial(mjSpec* s, mjsDefault* def);
 // Add pair to model.
-MJAPI mjmPair* mjm_addPair(mjSpec* s, mjmDefault* def);
+MJAPI mjsPair* mjs_addPair(mjSpec* s, mjsDefault* def);
 // Add excluded body pair to model.
-MJAPI mjmExclude* mjm_addExclude(mjSpec* s);
+MJAPI mjsExclude* mjs_addExclude(mjSpec* s);
 // Add equality to model.
-MJAPI mjmEquality* mjm_addEquality(mjSpec* s, mjmDefault* def);
+MJAPI mjsEquality* mjs_addEquality(mjSpec* s, mjsDefault* def);
 // Add tendon to model.
-MJAPI mjmTendon* mjm_addTendon(mjSpec* s, mjmDefault* def);
+MJAPI mjsTendon* mjs_addTendon(mjSpec* s, mjsDefault* def);
 // Wrap site using tendon.
-MJAPI mjmWrap* mjm_wrapSite(mjmTendon* tendon, const char* name);
+MJAPI mjsWrap* mjs_wrapSite(mjsTendon* tendon, const char* name);
 // Wrap geom using tendon.
-MJAPI mjmWrap* mjm_wrapGeom(mjmTendon* tendon, const char* name, const char* sidesite);
+MJAPI mjsWrap* mjs_wrapGeom(mjsTendon* tendon, const char* name, const char* sidesite);
 // Wrap joint using tendon.
-MJAPI mjmWrap* mjm_wrapJoint(mjmTendon* tendon, const char* name, double coef);
+MJAPI mjsWrap* mjs_wrapJoint(mjsTendon* tendon, const char* name, double coef);
 // Wrap pulley using tendon.
-MJAPI mjmWrap* mjm_wrapPulley(mjmTendon* tendon, double divisor);
+MJAPI mjsWrap* mjs_wrapPulley(mjsTendon* tendon, double divisor);
 // Add actuator to model.
-MJAPI mjmActuator* mjm_addActuator(mjSpec* s, mjmDefault* def);
+MJAPI mjsActuator* mjs_addActuator(mjSpec* s, mjsDefault* def);
 // Add sensor to model.
-MJAPI mjmSensor* mjm_addSensor(mjSpec* s);
+MJAPI mjsSensor* mjs_addSensor(mjSpec* s);
 // Add numeric to model.
-MJAPI mjmNumeric* mjm_addNumeric(mjSpec* s);
+MJAPI mjsNumeric* mjs_addNumeric(mjSpec* s);
 // Add text to model.
-MJAPI mjmText* mjm_addText(mjSpec* s);
+MJAPI mjsText* mjs_addText(mjSpec* s);
 // Add tuple to model.
-MJAPI mjmTuple* mjm_addTuple(mjSpec* s);
+MJAPI mjsTuple* mjs_addTuple(mjSpec* s);
 // Add keyframe to model.
-MJAPI mjmKey* mjm_addKey(mjSpec* s);
+MJAPI mjsKey* mjs_addKey(mjSpec* s);
 // Add plugin to model.
-MJAPI mjmPlugin* mjm_addPlugin(mjSpec* s);
+MJAPI mjsPlugin* mjs_addPlugin(mjSpec* s);
 // Add default to model.
-MJAPI mjmDefault* mjm_addDefault(mjSpec* s, const char* classname, int parentid, int* id);
+MJAPI mjsDefault* mjs_addDefault(mjSpec* s, const char* classname, int parentid, int* id);
 // Get model spec from body.
-MJAPI mjSpec* mjm_getSpec(mjmBody* body);
+MJAPI mjSpec* mjs_getSpec(mjsBody* body);
 // Get default corresponding to an mjElement.
-MJAPI mjmDefault* mjm_getDefault(mjElement element);
+MJAPI mjsDefault* mjs_getDefault(mjElement* element);
 // Find default in model by class name.
-MJAPI mjmDefault* mjm_findDefault(mjSpec* s, const char* classname);
+MJAPI mjsDefault* mjs_findDefault(mjSpec* s, const char* classname);
 // Get global default from model.
-MJAPI mjmDefault* mjm_getSpecDefault(mjSpec* s);
+MJAPI mjsDefault* mjs_getSpecDefault(mjSpec* s);
 // Find body in model by name.
-MJAPI mjmBody* mjm_findBody(mjSpec* s, const char* name);
+MJAPI mjsBody* mjs_findBody(mjSpec* s, const char* name);
 // Find child body by name.
-MJAPI mjmBody* mjm_findChild(mjmBody* body, const char* name);
+MJAPI mjsBody* mjs_findChild(mjsBody* body, const char* name);
 // Find mesh by name.
-MJAPI mjmMesh* mjm_findMesh(mjSpec* s, const char* name);
+MJAPI mjsMesh* mjs_findMesh(mjSpec* s, const char* name);
 // Find frame by name.
 MJAPI mjsFrame* mjs_findFrame(mjSpec* s, const char* name);
 // Get element id.
-MJAPI int mjm_getId(mjElement element);
+MJAPI int mjs_getId(mjElement* element);
 // Copy text to string.
-MJAPI void mjm_setString(mjString dest, const char* text);
+MJAPI void mjs_setString(mjString dest, const char* text);
 // Split text to entries and copy to string vector.
-MJAPI void mjm_setStringVec(mjStringVec dest, const char* text);
+MJAPI void mjs_setStringVec(mjStringVec dest, const char* text);
 // Set entry in string vector.
-MJAPI mjtByte mjm_setInStringVec(mjStringVec dest, int i, const char* text);
+MJAPI mjtByte mjs_setInStringVec(mjStringVec dest, int i, const char* text);
 // Append text entry to string vector.
-MJAPI void mjm_appendString(mjStringVec dest, const char* text);
+MJAPI void mjs_appendString(mjStringVec dest, const char* text);
 // Copy int array to vector.
-MJAPI void mjm_setInt(mjIntVec dest, const int* array, int size);
+MJAPI void mjs_setInt(mjIntVec dest, const int* array, int size);
 // Append int array to vector of arrays.
-MJAPI void mjm_appendIntVec(mjIntVecVec dest, const int* array, int size);
+MJAPI void mjs_appendIntVec(mjIntVecVec dest, const int* array, int size);
 // Copy float array to vector.
-MJAPI void mjm_setFloat(mjFloatVec dest, const float* array, int size);
+MJAPI void mjs_setFloat(mjFloatVec dest, const float* array, int size);
 // Append float array to vector of arrays.
-MJAPI void mjm_appendFloatVec(mjFloatVecVec dest, const float* array, int size);
+MJAPI void mjs_appendFloatVec(mjFloatVecVec dest, const float* array, int size);
 // Copy double array to vector.
-MJAPI void mjm_setDouble(mjDoubleVec dest, const double* array, int size);
+MJAPI void mjs_setDouble(mjDoubleVec dest, const double* array, int size);
 // Get string contents.
-MJAPI const char* mjm_getString(mjString source);
+MJAPI const char* mjs_getString(mjString source);
 // Get double array contents and optionally its size.
-MJAPI const double* mjm_getDouble(mjDoubleVec source, int* size);
+MJAPI const double* mjs_getDouble(mjDoubleVec source, int* size);
 // Set plugin attributes.
-MJAPI void mjm_setPluginAttributes(mjmPlugin* plugin, void* attributes);
+MJAPI void mjs_setPluginAttributes(mjsPlugin* plugin, void* attributes);
 // Set active plugins.
-MJAPI void mjm_setActivePlugins(mjSpec* s, void* activeplugins);
+MJAPI void mjs_setActivePlugins(mjSpec* s, void* activeplugins);
 // Set default.
-MJAPI void mjm_setDefault(mjElement element, mjmDefault* def);
+MJAPI void mjs_setDefault(mjElement* element, mjsDefault* def);
 // Set frame.
-MJAPI void mjm_setFrame(mjElement dest, mjmFrame* frame);
+MJAPI void mjs_setFrame(mjElement* dest, mjsFrame* frame);
 // Resolve alternative orientations to quat.
 MJAPI const char* mjs_resolveOrientation(double quat[4], mjtByte degree, const char* sequence,
                                         const mjsOrientation* orientation);
 // Compute quat and inertia from body->fullinertia.
-MJAPI const char* mjm_setFullInertia(mjmBody* body, double quat[4], double inertia[3]);
+MJAPI const char* mjs_setFullInertia(mjsBody* body, double quat[4], double inertia[3]);
 //---------------------------------- Initialization functions --------------------------------------
 // Default model attributes.
-MJAPI void mjm_defaultSpec(mjSpec& model);
+MJAPI void mjs_defaultSpec(mjSpec& model);
 // Default orientation attributes.
 MJAPI void mjs_defaultOrientation(mjsOrientation& orient);
 // Default body attributes.
-MJAPI void mjm_defaultBody(mjmBody& body);
+MJAPI void mjs_defaultBody(mjsBody& body);
 // Default frame attributes.
-MJAPI void mjm_defaultFrame(mjmFrame& frame);
+MJAPI void mjs_defaultFrame(mjsFrame& frame);
 // Default joint attributes.
-MJAPI void mjm_defaultJoint(mjmJoint& joint);
+MJAPI void mjs_defaultJoint(mjsJoint& joint);
 // Default geom attributes.
-MJAPI void mjm_defaultGeom(mjmGeom& geom);
+MJAPI void mjs_defaultGeom(mjsGeom& geom);
 // Default site attributes.
-MJAPI void mjm_defaultSite(mjmSite& site);
+MJAPI void mjs_defaultSite(mjsSite& site);
 // Default camera attributes.
-MJAPI void mjm_defaultCamera(mjmCamera& camera);
+MJAPI void mjs_defaultCamera(mjsCamera& camera);
 // Default light attributes.
-MJAPI void mjm_defaultLight(mjmLight& light);
+MJAPI void mjs_defaultLight(mjsLight& light);
 // Default flex attributes.
-MJAPI void mjm_defaultFlex(mjmFlex& flex);
+MJAPI void mjs_defaultFlex(mjsFlex& flex);
 // Default mesh attributes.
-MJAPI void mjm_defaultMesh(mjmMesh& mesh);
+MJAPI void mjs_defaultMesh(mjsMesh& mesh);
 // Default height field attributes.
-MJAPI void mjm_defaultHField(mjmHField& hfield);
+MJAPI void mjs_defaultHField(mjsHField& hfield);
 // Default skin attributes.
-MJAPI void mjm_defaultSkin(mjmSkin& skin);
+MJAPI void mjs_defaultSkin(mjsSkin& skin);
 // Default texture attributes.
-MJAPI void mjm_defaultTexture(mjmTexture& texture);
+MJAPI void mjs_defaultTexture(mjsTexture& texture);
 // Default material attributes.
-MJAPI void mjm_defaultMaterial(mjmMaterial& material);
+MJAPI void mjs_defaultMaterial(mjsMaterial& material);
 // Default pair attributes.
-MJAPI void mjm_defaultPair(mjmPair& pair);
+MJAPI void mjs_defaultPair(mjsPair& pair);
 // Default equality attributes.
-MJAPI void mjm_defaultEquality(mjmEquality& equality);
+MJAPI void mjs_defaultEquality(mjsEquality& equality);
 // Default tendon attributes.
-MJAPI void mjm_defaultTendon(mjmTendon& tendon);
+MJAPI void mjs_defaultTendon(mjsTendon& tendon);
 // Default actuator attributes.
-MJAPI void mjm_defaultActuator(mjmActuator& actuator);
+MJAPI void mjs_defaultActuator(mjsActuator& actuator);
 // Default sensor attributes.
-MJAPI void mjm_defaultSensor(mjmSensor& sensor);
+MJAPI void mjs_defaultSensor(mjsSensor& sensor);
 // Default numeric attributes.
-MJAPI void mjm_defaultNumeric(mjmNumeric& numeric);
+MJAPI void mjs_defaultNumeric(mjsNumeric& numeric);
 // Default text attributes.
-MJAPI void mjm_defaultText(mjmText& text);
+MJAPI void mjs_defaultText(mjsText& text);
 // Default tuple attributes.
-MJAPI void mjm_defaultTuple(mjmTuple& tuple);
+MJAPI void mjs_defaultTuple(mjsTuple& tuple);
 // Default keyframe attributes.
-MJAPI void mjm_defaultKey(mjmKey& key);
+MJAPI void mjs_defaultKey(mjsKey& key);
 // Default plugin attributes.
-MJAPI void mjm_defaultPlugin(mjmPlugin& plugin);
+MJAPI void mjs_defaultPlugin(mjsPlugin& plugin);
 //------------------------- Cache functions ------------------------------------
 typedef struct _mjCache* mjCache;
 // Set the size of the cache in bytes.
 MJAPI void mj_setCacheSize(mjCache cache, size_t size);
 // Get internal global cache context.
 MJAPI mjCache mj_globalCache();
 #ifdef __cplusplus
 }
@@ -39,7 +39,8 @@ template<typename T> std::size_t mjCAsset::Add(const std::string& name,
  const uint8_t* ptr = reinterpret_cast<const uint8_t*>(data);
  mjCAssetData& block = it->second;
-  block.bytes = std::make_shared<uint8_t[]>(nbytes);
+  block.bytes = std::shared_ptr<uint8_t>(new uint8_t[nbytes],
                                        [](uint8_t *p) {delete [] p;});
  std::copy(ptr, ptr + nbytes, block.bytes.get());
  block.nbytes = nbytes;
  nbytes_ += nbytes;
@@ -30,7 +30,7 @@
 // data associated with an asset
 struct mjCAssetData {
-  std::shared_ptr<uint8_t[]> bytes;  // raw serialized bytes of cached data
+  std::shared_ptr<uint8_t> bytes;    // raw serialized bytes of cached data
  std::size_t nbytes;                // number of bytes stored
 };
@@ -80,6 +80,11 @@ class mjCAsset {
    return blocks_.find(name) != blocks_.end();
  }
  const std::string& Timestamp() const { return timestamp_; }
  const std::string& Id() const { return id_; }
  std::size_t InsertNum() const { return insert_num_; }
  std::size_t AccessCount() const { return access_count_; }
 private:
  mjCAsset() = default;
@@ -105,10 +110,6 @@ class mjCAsset {
  void SetTimestamp(std::string timestamp) { timestamp_ = timestamp; }
  // accessors
  const std::string& Id() const { return id_; }
  const std::string& Timestamp() const { return timestamp_; }
  std::size_t InsertNum() const { return insert_num_; }
  std::size_t AccessCount() const { return access_count_; }
  std::size_t BytesCount() const { return nbytes_; }
  const std::unordered_map<std::string, mjCAssetData>& Blocks() const {
    return blocks_;
@@ -128,14 +129,23 @@ class mjCAsset {
  std::set<std::string> references_;
 };
 struct mjCAssetCompare {
  bool operator()(const mjCAsset* e1, const mjCAsset* e2) const {
    if (e1->AccessCount() != e2->AccessCount()) {
      return e1->AccessCount() < e2->AccessCount();
    }
    return e1->InsertNum() < e2->InsertNum();
  }
 };
 // the class container for a thread-safe asset cache
 class mjCCache {
 public:
  explicit mjCCache(std::size_t size)  :  max_size_(size) {}
  // move only
-  mjCCache(mjCCache&& other) = default;
+  mjCCache(mjCCache&& other) = delete;
-  mjCCache& operator=(mjCCache&& other) = default;
+  mjCCache& operator=(mjCCache&& other) = delete;
  mjCCache(const mjCCache& other) = delete;
  mjCCache& operator=(const mjCCache& other) = delete;
@@ -186,20 +196,11 @@ class mjCCache {
  std::size_t size_ = 0;        // current size of the cache in bytes
  std::size_t max_size_ = 0;    // max size of the cache in bytes
  // compare function for the priority queue
  static constexpr auto compare_ = [](const mjCAsset* e1,
                                      const mjCAsset* e2) {
    if (e1->AccessCount() != e2->AccessCount()) {
      return e1->AccessCount() < e2->AccessCount();
    }
    return e1->InsertNum() < e2->InsertNum();
  };
  // internal constant look up table for assets
  std::unordered_map<std::string, mjCAsset> lookup_;
  // internal priority queue for the cache
-  std::set<mjCAsset*, decltype(compare_)> entries_;
+  std::set<mjCAsset*, mjCAssetCompare> entries_;
  // models using the cache along with the assets they reference
  std::unordered_map<std::string, std::unordered_set<mjCAsset*>> models_;
@@ -66,7 +66,7 @@ mjCComposite::mjCComposite(void) {
  mj_defaultSolRefImp(solrefsmooth, solimpsmooth);
  // plugin variables
-  mjm_defaultPlugin(plugin);
+  mjs_defaultPlugin(plugin);
  plugin_name = "";
  plugin_instance_name = "";
  plugin.name = (mjString)&plugin_name;
@@ -223,7 +223,7 @@ void mjCComposite::SetDefault(void) {
 // make composite object
-bool mjCComposite::Make(mjSpec* spec, mjmBody* body, char* error, int error_sz) {
+bool mjCComposite::Make(mjSpec* spec, mjsBody* body, char* error, int error_sz) {
  mjCModel* model = (mjCModel*)spec->element;
  // check geom type
@@ -306,7 +306,7 @@ bool mjCComposite::Make(mjSpec* spec, mjmBody* body, char* error, int error_sz)
  // overwrite plugin name
  if (plugin_instance_name.empty() && plugin.active) {
    plugin_instance_name = "composite" + prefix;
-    ((mjCPlugin*)plugin.instance)->name = plugin_instance_name;
+    (static_cast<mjCPlugin*>(plugin.instance))->name = plugin_instance_name;
  }
  // dispatch
@@ -350,7 +350,7 @@ bool mjCComposite::Make(mjSpec* spec, mjmBody* body, char* error, int error_sz)
-bool mjCComposite::MakeParticle(mjCModel* model, mjmBody* body, char* error, int error_sz) {
+bool mjCComposite::MakeParticle(mjCModel* model, mjsBody* body, char* error, int error_sz) {
  char txt[100];
  std::vector<int> face;
@@ -432,7 +432,7 @@ bool mjCComposite::MakeParticle(mjCModel* model, mjmBody* body, char* error, int
  mjtNum t = 1;
  if (dim == 2 && plugin.active) {
    try {
-      mjCPlugin* pplugin = (mjCPlugin*)plugin.instance;
+      mjCPlugin* pplugin = static_cast<mjCPlugin*>(plugin.instance);
      t = std::stod(pplugin->config_attribs["thickness"], nullptr);
    } catch (const std::invalid_argument& e) {
      return comperr(error, "Invalid thickness attribute", error_sz);
@@ -464,13 +464,13 @@ bool mjCComposite::MakeParticle(mjCModel* model, mjmBody* body, char* error, int
  // create bodies and geoms
  for (int i=0; i<uservert.size()/3; i++) {
    // create body
-    mjmBody* b = mjm_addBody(body, NULL);
+    mjsBody* b = mjs_addBody(body, NULL);
    if (!username.empty()) {
-      mjm_setString(b->name, username[i].c_str());
+      mjs_setString(b->name, username[i].c_str());
    } else {
      mju::sprintf_arr(txt, "%sB%d", prefix.c_str(), i);
-      mjm_setString(b->name, txt);
+      mjs_setString(b->name, txt);
    }
    // set body position
@@ -481,8 +481,8 @@ bool mjCComposite::MakeParticle(mjCModel* model, mjmBody* body, char* error, int
    // add slider joints if none defined
    if (!add[mjCOMPKIND_PARTICLE]) {
      for (int i=0; i<3; i++) {
-        mjmJoint* jnt = mjm_addJoint(b, &defjoint[mjCOMPKIND_JOINT][0].spec);
+        mjsJoint* jnt = mjs_addJoint(b, &defjoint[mjCOMPKIND_JOINT][0].spec);
-        mjm_setDefault(jnt->element, mjm_getDefault(body->element));
+        mjs_setDefault(jnt->element, mjs_getDefault(body->element));
        jnt->type = mjJNT_SLIDE;
        mjuu_setvec(jnt->pos, 0, 0, 0);
        mjuu_setvec(jnt->axis, 0, 0, 0);
@@ -493,30 +493,30 @@ bool mjCComposite::MakeParticle(mjCModel* model, mjmBody* body, char* error, int
    // add user-specified joints
    else {
      for (auto defjnt : defjoint[mjCOMPKIND_PARTICLE]) {
-        mjmJoint* jnt = mjm_addJoint(b, &defjnt.spec);
+        mjsJoint* jnt = mjs_addJoint(b, &defjnt.spec);
-        mjm_setDefault(jnt->element, mjm_getDefault(body->element));
+        mjs_setDefault(jnt->element, mjs_getDefault(body->element));
      }
    }
    // add geom
-    mjmGeom* g = mjm_addGeom(b, &def[0].spec);
+    mjsGeom* g = mjs_addGeom(b, &def[0].spec);
-    mjm_setDefault(g->element, mjm_getDefault(body->element));
+    mjs_setDefault(g->element, mjs_getDefault(body->element));
    // add site
-    mjmSite* s = mjm_addSite(b, &def[0].spec);
+    mjsSite* s = mjs_addSite(b, &def[0].spec);
-    mjm_setDefault(s->element, mjm_getDefault(body->element));
+    mjs_setDefault(s->element, mjs_getDefault(body->element));
    s->type = mjGEOM_SPHERE;
    mju::sprintf_arr(txt, "%sS%d", prefix.c_str(), i);
-    mjm_setString(s->name, txt);
+    mjs_setString(s->name, txt);
    // add plugin
    if (plugin.active) {
-      mjmPlugin* pplugin = &b->plugin;
+      mjsPlugin* pplugin = &b->plugin;
-      mjCPlugin* cplugin = (mjCPlugin*)plugin.instance;
+      mjCPlugin* cplugin = static_cast<mjCPlugin*>(plugin.instance);
      pplugin->active = true;
-      pplugin->instance = (mjElement)plugin.instance;
+      pplugin->instance = plugin.instance;
-      mjm_setString(pplugin->instance_name, plugin_instance_name.c_str());
+      mjs_setString(pplugin->instance_name, plugin_instance_name.c_str());
-      mjm_setString(pplugin->name, mjm_getString(plugin.name));
+      mjs_setString(pplugin->name, mjs_getString(plugin.name));
      if (i==0 && !cplugin->config_attribs["face"].empty()) {
        return comperr(error, "Face attribute already exists in plugin", error_sz);
@@ -560,18 +560,18 @@ bool mjCComposite::MakeParticle(mjCModel* model, mjmBody* body, char* error, int
      mju::sprintf_arr(txt2, "%sS%d", prefix.c_str(), v1);
      // create tendon
-      mjmTendon* ten = mjm_addTendon(&model->spec, &def[mjCOMPKIND_TENDON].spec);
+      mjsTendon* ten = mjs_addTendon(&model->spec, &def[mjCOMPKIND_TENDON].spec);
-      mjm_setDefault(ten->element, &model->defaults[0]->spec);
+      mjs_setDefault(ten->element, &model->defaults[0]->spec);
-      mjm_setString(ten->name, txt0);
+      mjs_setString(ten->name, txt0);
      ten->group = 4;
-      mjm_wrapSite(ten, txt1);
+      mjs_wrapSite(ten, txt1);
-      mjm_wrapSite(ten, txt2);
+      mjs_wrapSite(ten, txt2);
      // add equality constraint
-      mjmEquality* eq = mjm_addEquality(&model->spec, &def[mjCOMPKIND_TENDON].spec);
+      mjsEquality* eq = mjs_addEquality(&model->spec, &def[mjCOMPKIND_TENDON].spec);
-      mjm_setDefault(eq->element, &model->defaults[0]->spec);
+      mjs_setDefault(eq->element, &model->defaults[0]->spec);
      eq->type = mjEQ_TENDON;
-      mjm_setString(eq->name1, mjm_getString(ten->name));
+      mjs_setString(eq->name1, mjs_getString(ten->name));
    }
  }
@@ -593,7 +593,7 @@ bool mjCComposite::MakeParticle(mjCModel* model, mjmBody* body, char* error, int
 // make grid connected with tendons
-bool mjCComposite::MakeGrid(mjCModel* model, mjmBody* body, char* error, int error_sz) {
+bool mjCComposite::MakeGrid(mjCModel* model, mjsBody* body, char* error, int error_sz) {
  char txt[100], txt1[100], txt2[100];
  // check dimensionality
@@ -615,9 +615,9 @@ bool mjCComposite::MakeGrid(mjCModel* model, mjmBody* body, char* error, int err
  for (int ix=0; ix<count[0]; ix++) {
    for (int iy=0; iy<count[1]; iy++) {
      // create body
-      mjmBody* b = mjm_addBody(body, NULL);
+      mjsBody* b = mjs_addBody(body, NULL);
      mju::sprintf_arr(txt, "%sB%d_%d", prefix.c_str(), ix, iy);
-      mjm_setString(b->name, txt);
+      mjs_setString(b->name, txt);
      // set body position
      b->pos[0] = offset[0] + spacing*(ix - 0.5*count[0]);
@@ -625,18 +625,18 @@ bool mjCComposite::MakeGrid(mjCModel* model, mjmBody* body, char* error, int err
      b->pos[2] = offset[2];
      // add geom
-      mjmGeom* g = mjm_addGeom(b, &def[0].spec);
+      mjsGeom* g = mjs_addGeom(b, &def[0].spec);
-      mjm_setDefault(g->element, mjm_getDefault(body->element));
+      mjs_setDefault(g->element, mjs_getDefault(body->element));
      g->type = mjGEOM_SPHERE;
      mju::sprintf_arr(txt, "%sG%d_%d", prefix.c_str(), ix, iy);
-      mjm_setString(g->name, txt);
+      mjs_setString(g->name, txt);
      // add site
-      mjmSite* s = mjm_addSite(b, &def[0].spec);
+      mjsSite* s = mjs_addSite(b, &def[0].spec);
-      mjm_setDefault(s->element, mjm_getDefault(body->element));
+      mjs_setDefault(s->element, mjs_getDefault(body->element));
      s->type = mjGEOM_SPHERE;
      mju::sprintf_arr(txt, "%sS%d_%d", prefix.c_str(), ix, iy);
-      mjm_setString(s->name, txt);
+      mjs_setString(s->name, txt);
      // skip pinned elements
      bool skip = false;
@@ -651,12 +651,12 @@ bool mjCComposite::MakeGrid(mjCModel* model, mjmBody* body, char* error, int err
      }
      // add slider joint
-      mjmJoint* jnt[3];
+      mjsJoint* jnt[3];
      for (int i=0; i<3; i++) {
-        jnt[i] = mjm_addJoint(b, &defjoint[mjCOMPKIND_JOINT][0].spec);
+        jnt[i] = mjs_addJoint(b, &defjoint[mjCOMPKIND_JOINT][0].spec);
-        mjm_setDefault(jnt[i]->element, mjm_getDefault(body->element));
+        mjs_setDefault(jnt[i]->element, mjs_getDefault(body->element));
        mju::sprintf_arr(txt, "%sJ%d_%d_%d", prefix.c_str(), i, ix, iy);
-        mjm_setString(jnt[i]->name, txt);
+        mjs_setString(jnt[i]->name, txt);
        jnt[i]->type = mjJNT_SLIDE;
        mjuu_setvec(jnt[i]->pos, 0, 0, 0);
        mjuu_setvec(jnt[i]->axis, 0, 0, 0);
@@ -682,10 +682,10 @@ bool mjCComposite::MakeGrid(mjCModel* model, mjmBody* body, char* error, int err
        ten->WrapSite(txt2);
        // add equality constraint
-        mjmEquality* eq = mjm_addEquality(&model->spec, &def[mjCOMPKIND_TENDON].spec);
+        mjsEquality* eq = mjs_addEquality(&model->spec, &def[mjCOMPKIND_TENDON].spec);
-        mjm_setDefault(eq->element, &model->defaults[0]->spec);
+        mjs_setDefault(eq->element, &model->defaults[0]->spec);
        eq->type = mjEQ_TENDON;
-        mjm_setString(eq->name1, ten->name.c_str());
+        mjs_setString(eq->name1, ten->name.c_str());
      }
    }
  }
@@ -709,7 +709,7 @@ bool mjCComposite::MakeGrid(mjCModel* model, mjmBody* body, char* error, int err
-bool mjCComposite::MakeCable(mjCModel* model, mjmBody* body, char* error, int error_sz) {
+bool mjCComposite::MakeCable(mjCModel* model, mjsBody* body, char* error, int error_sz) {
  // check dim
  if (dim!=1) {
    return comperr(error, "Cable must be one-dimensional", error_sz);
@@ -723,9 +723,9 @@ bool mjCComposite::MakeCable(mjCModel* model, mjmBody* body, char* error, int er
  }
  // add name to model
-  mjmText* pte = mjm_addText(&model->spec);
+  mjsText* pte = mjs_addText(&model->spec);
-  mjm_setString(pte->name, ("composite_" + prefix).c_str());
+  mjs_setString(pte->name, ("composite_" + prefix).c_str());
-  mjm_setString(pte->data, ("rope_" + prefix).c_str());
+  mjs_setString(pte->data, ("rope_" + prefix).c_str());
  // populate uservert if not specified
  if (uservert.empty()) {
@@ -780,7 +780,7 @@ bool mjCComposite::MakeCable(mjCModel* model, mjmBody* body, char* error, int er
-mjmBody* mjCComposite::AddCableBody(mjCModel* model, mjmBody* body, int ix, mjtNum normal[3], mjtNum prev_quat[4]) {
+mjsBody* mjCComposite::AddCableBody(mjCModel* model, mjsBody* body, int ix, mjtNum normal[3], mjtNum prev_quat[4]) {
  char txt_geom[100], txt_site[100], txt_slide[100];
  char this_body[100], next_body[100], this_joint[100];
  mjtNum dquat[4], this_quat[4];
@@ -836,8 +836,8 @@ mjmBody* mjCComposite::AddCableBody(mjCModel* model, mjmBody* body, int ix, mjtN
  mju::sprintf_arr(txt_slide, "%sJs%d", prefix.c_str(), ix);
  // add body
-  body = mjm_addBody(body, 0);
+  body = mjs_addBody(body, 0);
-  mjm_setString(body->name, this_body);
+  mjs_setString(body->name, this_body);
  if (first) {
    mjuu_setvec(body->pos, offset[0]+uservert[3*ix],
                           offset[1]+uservert[3*ix+1],
@@ -851,9 +851,9 @@ mjmBody* mjCComposite::AddCableBody(mjCModel* model, mjmBody* body, int ix, mjtN
  }
  // add geom
-  mjmGeom* geom = mjm_addGeom(body, &def[0].spec);
+  mjsGeom* geom = mjs_addGeom(body, &def[0].spec);
-  mjm_setDefault(geom->element, mjm_getDefault(body->element));
+  mjs_setDefault(geom->element, mjs_getDefault(body->element));
-  mjm_setString(geom->name, txt_geom);
+  mjs_setString(geom->name, txt_geom);
  if (def[0].spec.geom->type==mjGEOM_CYLINDER ||
      def[0].spec.geom->type==mjGEOM_CAPSULE) {
    mjuu_zerovec(geom->fromto, 6);
@@ -866,11 +866,11 @@ mjmBody* mjCComposite::AddCableBody(mjCModel* model, mjmBody* body, int ix, mjtN
  // add plugin
  if (plugin.active) {
-    mjmPlugin* pplugin = &body->plugin;
+    mjsPlugin* pplugin = &body->plugin;
    pplugin->active = true;
-    pplugin->instance = (mjElement)plugin.instance;
+    pplugin->instance = plugin.instance;
-    mjm_setString(pplugin->name, mjm_getString(plugin.name));
+    mjs_setString(pplugin->name, mjs_getString(plugin.name));
-    mjm_setString(pplugin->instance_name, plugin_instance_name.c_str());
+    mjs_setString(pplugin->instance_name, plugin_instance_name.c_str());
  }
  // update orientation
@@ -878,27 +878,27 @@ mjmBody* mjCComposite::AddCableBody(mjCModel* model, mjmBody* body, int ix, mjtN
  // add curvature joint
  if (!first || strcmp(initial.c_str(), "none")) {
-    mjmJoint* jnt = mjm_addJoint(body, &defjoint[mjCOMPKIND_JOINT][0].spec);
+    mjsJoint* jnt = mjs_addJoint(body, &defjoint[mjCOMPKIND_JOINT][0].spec);
-    mjm_setDefault(jnt->element, mjm_getDefault(body->element));
+    mjs_setDefault(jnt->element, mjs_getDefault(body->element));
    jnt->type = (first && strcmp(initial.c_str(), "free")==0) ? mjJNT_FREE : mjJNT_BALL;
    jnt->damping = jnt->type==mjJNT_FREE ? 0 : jnt->damping;
    jnt->armature = jnt->type==mjJNT_FREE ? 0 : jnt->armature;
    jnt->frictionloss = jnt->type==mjJNT_FREE ? 0 : jnt->frictionloss;
-    mjm_setString(jnt->name, this_joint);
+    mjs_setString(jnt->name, this_joint);
  }
  // exclude contact pair
  if (!last) {
-    mjmExclude* exclude = mjm_addExclude(&model->spec);
+    mjsExclude* exclude = mjs_addExclude(&model->spec);
-    mjm_setString(exclude->bodyname1, std::string(this_body).c_str());
+    mjs_setString(exclude->bodyname1, std::string(this_body).c_str());
-    mjm_setString(exclude->bodyname2, std::string(next_body).c_str());
+    mjs_setString(exclude->bodyname2, std::string(next_body).c_str());
  }
  // add site at the boundary
  if (last || first) {
-    mjmSite* site = mjm_addSite(body, &def[0].spec);
+    mjsSite* site = mjs_addSite(body, &def[0].spec);
-    mjm_setDefault(site->element, mjm_getDefault(body->element));
+    mjs_setDefault(site->element, mjs_getDefault(body->element));
-    mjm_setString(site->name, txt_site);
+    mjs_setString(site->name, txt_site);
    mjuu_setvec(site->pos, last ? length : 0, 0, 0);
    mjuu_setvec(site->quat, 1, 0, 0, 0);
  }
@@ -908,7 +908,7 @@ mjmBody* mjCComposite::AddCableBody(mjCModel* model, mjmBody* body, int ix, mjtN
 // make rope
-bool mjCComposite::MakeRope(mjCModel* model, mjmBody* body, char* error, int error_sz) {
+bool mjCComposite::MakeRope(mjCModel* model, mjsBody* body, char* error, int error_sz) {
  // check dim
  if (dim!=1) {
    return comperr(error, "Rope must be one-dimensional", error_sz);
@@ -917,7 +917,7 @@ bool mjCComposite::MakeRope(mjCModel* model, mjmBody* body, char* error, int err
  // check root body name prefix
  char txt[200];
  mju::sprintf_arr(txt, "%sB", prefix.c_str());
-  std::string body_name = mjm_getString(body->name);
+  std::string body_name = mjs_getString(body->name);
  if (std::strncmp(txt, body_name.substr(0, strlen(txt)).c_str(), mju::sizeof_arr(txt))) {
    mju::strcat_arr(txt, " must be the beginning of root body name");
    return comperr(error, txt, error_sz);
@@ -937,7 +937,7 @@ bool mjCComposite::MakeRope(mjCModel* model, mjmBody* body, char* error, int err
  AddRopeBody(model, body, ox, ox);
  // add elements: right
-  mjmBody* pbody = body;
+  mjsBody* pbody = body;
  for (int ix=ox; ix<count[0]-1; ix++) {
    pbody = AddRopeBody(model, pbody, ix, ix+1);
  }
@@ -953,20 +953,20 @@ bool mjCComposite::MakeRope(mjCModel* model, mjmBody* body, char* error, int err
    char txt2[200];
    // add equality constraint
-    mjmEquality* eq = mjm_addEquality(&model->spec, 0);
+    mjsEquality* eq = mjs_addEquality(&model->spec, 0);
    eq->type = mjEQ_CONNECT;
    mju::sprintf_arr(txt, "%sB0", prefix.c_str());
    mju::sprintf_arr(txt2, "%sB%d", prefix.c_str(), count[0]-1);
-    mjm_setString(eq->name1, txt);
+    mjs_setString(eq->name1, txt);
-    mjm_setString(eq->name2, txt2);
+    mjs_setString(eq->name2, txt2);
    mjuu_setvec(eq->data, -0.5*spacing, 0, 0);
    mju_copy(eq->solref, solrefsmooth, mjNREF);
    mju_copy(eq->solimp, solimpsmooth, mjNIMP);
    // remove contact between connected bodies
-    mjmExclude* pair = mjm_addExclude(&model->spec);
+    mjsExclude* pair = mjs_addExclude(&model->spec);
-    mjm_setString(pair->bodyname1, std::string(txt).c_str());
+    mjs_setString(pair->bodyname1, std::string(txt).c_str());
-    mjm_setString(pair->bodyname2, std::string(txt2).c_str());
+    mjs_setString(pair->bodyname2, std::string(txt2).c_str());
  }
  return true;
@@ -975,16 +975,16 @@ bool mjCComposite::MakeRope(mjCModel* model, mjmBody* body, char* error, int err
 // add child body for cloth
-mjmBody* mjCComposite::AddRopeBody(mjCModel* model, mjmBody* body, int ix, int ix1) {
+mjsBody* mjCComposite::AddRopeBody(mjCModel* model, mjsBody* body, int ix, int ix1) {
  char txt[100];
  bool isroot = (ix==ix1);
  double dx = spacing*(ix1-ix);
  // add child if not root
  if (!isroot) {
-    body = mjm_addBody(body, 0);
+    body = mjs_addBody(body, 0);
    mju::sprintf_arr(txt, "%sB%d", prefix.c_str(), ix1);
-    mjm_setString(body->name, txt);
+    mjs_setString(body->name, txt);
    // loop
    if (type==mjCOMPTYPE_LOOP) {
@@ -1007,10 +1007,10 @@ mjmBody* mjCComposite::AddRopeBody(mjCModel* model, mjmBody* body, int ix, int i
  }
  // add geom
-  mjmGeom* geom = mjm_addGeom(body, &def[0].spec);
+  mjsGeom* geom = mjs_addGeom(body, &def[0].spec);
-  mjm_setDefault(geom->element, mjm_getDefault(body->element));
+  mjs_setDefault(geom->element, mjs_getDefault(body->element));
  mju::sprintf_arr(txt, "%sG%d", prefix.c_str(), ix1);
-  mjm_setString(geom->name, txt);
+  mjs_setString(geom->name, txt);
  mjuu_setvec(geom->pos, 0, 0, 0);
  mjuu_setvec(geom->quat, sqrt(0.5), 0, sqrt(0.5), 0);
@@ -1022,10 +1022,10 @@ mjmBody* mjCComposite::AddRopeBody(mjCModel* model, mjmBody* body, int ix, int i
  // add main joint
  for (int i=0; i<2; i++) {
    // add joint
-    mjmJoint* jnt = mjm_addJoint(body, &defjoint[mjCOMPKIND_JOINT][0].spec);
+    mjsJoint* jnt = mjs_addJoint(body, &defjoint[mjCOMPKIND_JOINT][0].spec);
-    mjm_setDefault(jnt->element, mjm_getDefault(body->element));
+    mjs_setDefault(jnt->element, mjs_getDefault(body->element));
    mju::sprintf_arr(txt, "%sJ%d_%d", prefix.c_str(), i, ix1);
-    mjm_setString(jnt->name, txt);
+    mjs_setString(jnt->name, txt);
    jnt->type = mjJNT_HINGE;
    mjuu_setvec(jnt->pos, -0.5*dx, 0, 0);
    mjuu_setvec(jnt->axis, 0, 0, 0);
@@ -1035,37 +1035,37 @@ mjmBody* mjCComposite::AddRopeBody(mjCModel* model, mjmBody* body, int ix, int i
  // add twist joint
  if (add[mjCOMPKIND_TWIST]) {
    // add joint
-    mjmJoint* jnt = mjm_addJoint(body, &defjoint[mjCOMPKIND_TWIST][0].spec);
+    mjsJoint* jnt = mjs_addJoint(body, &defjoint[mjCOMPKIND_TWIST][0].spec);
-    mjm_setDefault(jnt->element, mjm_getDefault(body->element));
+    mjs_setDefault(jnt->element, mjs_getDefault(body->element));
    mju::sprintf_arr(txt, "%sJT%d", prefix.c_str(), ix1);
-    mjm_setString(jnt->name, txt);
+    mjs_setString(jnt->name, txt);
    jnt->type = mjJNT_HINGE;
    mjuu_setvec(jnt->pos, -0.5*dx, 0, 0);
    mjuu_setvec(jnt->axis, 1, 0, 0);
    // add constraint
-    mjmEquality* eq = mjm_addEquality(&model->spec, &def[mjCOMPKIND_TWIST].spec);
+    mjsEquality* eq = mjs_addEquality(&model->spec, &def[mjCOMPKIND_TWIST].spec);
-    mjm_setDefault(eq->element, &model->defaults[0]->spec);
+    mjs_setDefault(eq->element, &model->defaults[0]->spec);
    eq->type = mjEQ_JOINT;
-    mjm_setString(eq->name1, mjm_getString(jnt->name));
+    mjs_setString(eq->name1, mjs_getString(jnt->name));
  }
  // add stretch joint
  if (add[mjCOMPKIND_STRETCH]) {
    // add joint
-    mjmJoint* jnt = mjm_addJoint(body, &defjoint[mjCOMPKIND_STRETCH][0].spec);
+    mjsJoint* jnt = mjs_addJoint(body, &defjoint[mjCOMPKIND_STRETCH][0].spec);
-    mjm_setDefault(jnt->element, mjm_getDefault(body->element));
+    mjs_setDefault(jnt->element, mjs_getDefault(body->element));
    mju::sprintf_arr(txt, "%sJS%d", prefix.c_str(), ix1);
-    mjm_setString(jnt->name, txt);
+    mjs_setString(jnt->name, txt);
    jnt->type = mjJNT_SLIDE;
    mjuu_setvec(jnt->pos, -0.5*dx, 0, 0);
    mjuu_setvec(jnt->axis, 1, 0, 0);
    // add constraint
-    mjmEquality* eq = mjm_addEquality(&model->spec, &def[mjCOMPKIND_STRETCH].spec);
+    mjsEquality* eq = mjs_addEquality(&model->spec, &def[mjCOMPKIND_STRETCH].spec);
-    mjm_setDefault(eq->element,  &model->defaults[0]->spec);
+    mjs_setDefault(eq->element,  &model->defaults[0]->spec);
    eq->type = mjEQ_JOINT;
-    mjm_setString(eq->name1, mjm_getString(jnt->name));
+    mjs_setString(eq->name1, mjs_getString(jnt->name));
  }
  return body;
@@ -1110,7 +1110,7 @@ void mjCComposite::BoxProject(double* pos) {
 // make 3d box, ellipsoid or cylinder
-bool mjCComposite::MakeBox(mjCModel* model, mjmBody* body, char* error, int error_sz) {
+bool mjCComposite::MakeBox(mjCModel* model, mjsBody* body, char* error, int error_sz) {
  char txt[100];
  // check dim
@@ -1119,11 +1119,11 @@ bool mjCComposite::MakeBox(mjCModel* model, mjmBody* body, char* error, int erro
  }
  // center geom: two times bigger
-  mjmGeom* geom = mjm_addGeom(body, &def[0].spec);
+  mjsGeom* geom = mjs_addGeom(body, &def[0].spec);
-  mjm_setDefault(geom->element, mjm_getDefault(body->element));
+  mjs_setDefault(geom->element, mjs_getDefault(body->element));
  geom->type = mjGEOM_SPHERE;
  mju::sprintf_arr(txt, "%sGcenter", prefix.c_str());
-  mjm_setString(geom->name, txt);
+  mjs_setString(geom->name, txt);
  mjuu_setvec(geom->pos, 0, 0, 0);
  geom->size[0] *= 2;
  geom->size[1] = 0;
@@ -1143,9 +1143,9 @@ bool mjCComposite::MakeBox(mjCModel* model, mjmBody* body, char* error, int erro
            iy==0 || iy==count[1]-1 ||
            iz==0 || iz==count[2]-1) {
          // create body
-          mjmBody* b = mjm_addBody(body, NULL);
+          mjsBody* b = mjs_addBody(body, NULL);
          mju::sprintf_arr(txt, "%sB%d_%d_%d", prefix.c_str(), ix, iy, iz);
-          mjm_setString(b->name, txt);
+          mjs_setString(b->name, txt);
          // set body position (+/- 1)
          b->pos[0] = 2.0*ix/(count[0]-1) - 1;
@@ -1160,10 +1160,10 @@ bool mjCComposite::MakeBox(mjCModel* model, mjmBody* body, char* error, int erro
          mjuu_normvec(b->alt.zaxis, 3);
          // add geom
-          mjmGeom* g = mjm_addGeom(b, &def[0].spec);
+          mjsGeom* g = mjs_addGeom(b, &def[0].spec);
-          mjm_setDefault(g->element, mjm_getDefault(body->element));
+          mjs_setDefault(g->element, mjs_getDefault(body->element));
          mju::sprintf_arr(txt, "%sG%d_%d_%d", prefix.c_str(), ix, iy, iz);
-          mjm_setString(g->name, txt);
+          mjs_setString(g->name, txt);
          // offset inwards, enforce sphere or capsule
          if (g->type==mjGEOM_CAPSULE) {
@@ -1174,22 +1174,22 @@ bool mjCComposite::MakeBox(mjCModel* model, mjmBody* body, char* error, int erro
          }
          // add slider joint
-          mjmJoint* jnt = mjm_addJoint(b, &defjoint[mjCOMPKIND_JOINT][0].spec);
+          mjsJoint* jnt = mjs_addJoint(b, &defjoint[mjCOMPKIND_JOINT][0].spec);
-          mjm_setDefault(jnt->element, mjm_getDefault(body->element));
+          mjs_setDefault(jnt->element, mjs_getDefault(body->element));
          mju::sprintf_arr(txt, "%sJ%d_%d_%d", prefix.c_str(), ix, iy, iz);
-          mjm_setString(jnt->name, txt);
+          mjs_setString(jnt->name, txt);
          jnt->type = mjJNT_SLIDE;
          mjuu_setvec(jnt->pos, 0, 0, 0);
          mjuu_setvec(jnt->axis, 0, 0, 1);
          // add fix constraint
-          mjmEquality* eq = mjm_addEquality(&model->spec, &def[mjCOMPKIND_JOINT].spec);
+          mjsEquality* eq = mjs_addEquality(&model->spec, &def[mjCOMPKIND_JOINT].spec);
-          mjm_setDefault(eq->element,  &model->defaults[0]->spec);
+          mjs_setDefault(eq->element,  &model->defaults[0]->spec);
          eq->type = mjEQ_JOINT;
-          mjm_setString(eq->name1, mjm_getString(jnt->name));
+          mjs_setString(eq->name1, mjs_getString(jnt->name));
          // add joint to tendon
-          ten->WrapJoint(std::string(mjm_getString(jnt->name)), 1);
+          ten->WrapJoint(std::string(mjs_getString(jnt->name)), 1);
          // add neighbor constraints
          for (int i=0; i<3; i++) {
@@ -1203,12 +1203,12 @@ bool mjCComposite::MakeBox(mjCModel* model, mjmBody* body, char* error, int erro
              char txt2[200];
              mju::sprintf_arr(txt2,
                               "%sJ%d_%d_%d", prefix.c_str(), ix1, iy1, iz1);
-              mjmEquality* eqn = mjm_addEquality(&model->spec, 0);
+              mjsEquality* eqn = mjs_addEquality(&model->spec, 0);
              mju_copy(eqn->solref, solrefsmooth, mjNREF);
              mju_copy(eqn->solimp, solimpsmooth, mjNIMP);
              eqn->type = mjEQ_JOINT;
-              mjm_setString(eqn->name1, txt);
+              mjs_setString(eqn->name1, txt);
-              mjm_setString(eqn->name2, txt2);
+              mjs_setString(eqn->name2, txt2);
            }
          }
        }
@@ -1217,10 +1217,10 @@ bool mjCComposite::MakeBox(mjCModel* model, mjmBody* body, char* error, int erro
  }
  // finalize fixed tendon
-  mjmEquality* eqt = mjm_addEquality(&model->spec, &def[mjCOMPKIND_TENDON].spec);
+  mjsEquality* eqt = mjs_addEquality(&model->spec, &def[mjCOMPKIND_TENDON].spec);
-  mjm_setDefault(eqt->element, &model->defaults[0]->spec);
+  mjs_setDefault(eqt->element, &model->defaults[0]->spec);
  eqt->type = mjEQ_TENDON;
-  mjm_setString(eqt->name1, ten->name.c_str());
+  mjs_setString(eqt->name1, ten->name.c_str());
  // skin
  if (skin) {
@@ -1253,10 +1253,10 @@ void mjCComposite::MakeShear(mjCModel* model) {
      ten->name = txt;
      // equality constraint
-      mjmEquality* eq = mjm_addEquality(&model->spec, &def[mjCOMPKIND_SHEAR].spec);
+      mjsEquality* eq = mjs_addEquality(&model->spec, &def[mjCOMPKIND_SHEAR].spec);
-      mjm_setDefault(eq->element, &model->defaults[0]->spec);
+      mjs_setDefault(eq->element, &model->defaults[0]->spec);
      eq->type = mjEQ_TENDON;
-      mjm_setString(eq->name1, txt);
+      mjs_setString(eq->name1, txt);
    }
  }
 }
@@ -1264,18 +1264,18 @@ void mjCComposite::MakeShear(mjCModel* model) {
 // copy local vectors to skin
-void mjCComposite::CopyIntoSkin(mjmSkin* skin) {
+void mjCComposite::CopyIntoSkin(mjsSkin* skin) {
-  mjm_setInt(skin->face, face.data(), face.size());
+  mjs_setInt(skin->face, face.data(), face.size());
-  mjm_setFloat(skin->vert, vert.data(), vert.size());
+  mjs_setFloat(skin->vert, vert.data(), vert.size());
-  mjm_setFloat(skin->bindpos, bindpos.data(), bindpos.size());
+  mjs_setFloat(skin->bindpos, bindpos.data(), bindpos.size());
-  mjm_setFloat(skin->bindquat, bindquat.data(), bindquat.size());
+  mjs_setFloat(skin->bindquat, bindquat.data(), bindquat.size());
-  mjm_setFloat(skin->texcoord, texcoord.data(), texcoord.size());
+  mjs_setFloat(skin->texcoord, texcoord.data(), texcoord.size());
  for (int i=0; i<vertid.size(); i++) {
-    mjm_appendIntVec(skin->vertid, vertid[i].data(), vertid[i].size());
+    mjs_appendIntVec(skin->vertid, vertid[i].data(), vertid[i].size());
  }
  for (int i=0; i< vertweight.size(); i++) {
-    mjm_appendFloatVec(skin->vertweight, vertweight[i].data(), vertweight[i].size());
+    mjs_appendFloatVec(skin->vertweight, vertweight[i].data(), vertweight[i].size());
  }
  face.clear();
@@ -1295,10 +1295,10 @@ void mjCComposite::MakeSkin2(mjCModel* model, mjtNum inflate) {
  int N = count[0]*count[1];
  // add skin, set name and material
-  mjmSkin* skin = mjm_addSkin(&model->spec);
+  mjsSkin* skin = mjs_addSkin(&model->spec);
  mju::sprintf_arr(txt, "%sSkin", prefix.c_str());
-  mjm_setString(skin->name, txt);
+  mjs_setString(skin->name, txt);
-  mjm_setString(skin->material, skinmaterial.c_str());
+  mjs_setString(skin->material, skinmaterial.c_str());
  mjuu_copyvec(skin->rgba, skinrgba, 4);
  skin->inflate = inflate;
  skin->group = skingroup;
@@ -1316,7 +1316,7 @@ void mjCComposite::MakeSkin2(mjCModel* model, mjtNum inflate) {
        vert.push_back(0);
        mju::sprintf_arr(txt, "%sB%d", prefix.c_str(), i);
-        mjm_appendString(skin->bodyname, txt);
+        mjs_appendString(skin->bodyname, txt);
        bindpos.push_back(0);
        bindpos.push_back(0);
        bindpos.push_back(0);
@@ -1426,7 +1426,7 @@ void mjCComposite::MakeSkin2(mjCModel* model, mjtNum inflate) {
 // add bones in 2D
-void mjCComposite::MakeClothBones(mjCModel* model, mjmSkin* skin) {
+void mjCComposite::MakeClothBones(mjCModel* model, mjsSkin* skin) {
  char txt[100];
  int N = count[0]*count[1];
@@ -1441,7 +1441,7 @@ void mjCComposite::MakeClothBones(mjCModel* model, mjmSkin* skin) {
      }
      // bind pose
-      mjm_appendString(skin->bodyname, txt);
+      mjs_appendString(skin->bodyname, txt);
      bindpos.push_back(0);
      bindpos.push_back(0);
      bindpos.push_back(0);
@@ -1459,7 +1459,7 @@ void mjCComposite::MakeClothBones(mjCModel* model, mjmSkin* skin) {
-void mjCComposite::MakeClothBonesSubgrid(mjCModel* model, mjmSkin* skin) {
+void mjCComposite::MakeClothBonesSubgrid(mjCModel* model, mjsSkin* skin) {
  char txt[100];
  // populate bones
@@ -1473,7 +1473,7 @@ void mjCComposite::MakeClothBonesSubgrid(mjCModel* model, mjmSkin* skin) {
      }
      // bind pose
-      mjm_appendString(skin->bodyname, txt);
+      mjs_appendString(skin->bodyname, txt);
      bindpos.push_back(ix*spacing);
      bindpos.push_back(iy*spacing);
      bindpos.push_back(0);
@@ -1492,7 +1492,7 @@ void mjCComposite::MakeClothBonesSubgrid(mjCModel* model, mjmSkin* skin) {
 // add bones to 1D
-void mjCComposite::MakeCableBones(mjCModel* model, mjmSkin* skin) {
+void mjCComposite::MakeCableBones(mjCModel* model, mjsSkin* skin) {
  char this_body[100];
  int N = count[0]*count[1];
@@ -1510,14 +1510,14 @@ void mjCComposite::MakeCableBones(mjCModel* model, mjmSkin* skin) {
      // bind pose
      if (iy==0) {
-        mjm_appendString(skin->bodyname, this_body);
+        mjs_appendString(skin->bodyname, this_body);
        bindpos.push_back((ix==count[0]-1) ? -2*def[0].spec.geom->size[0] : 0);
        bindpos.push_back(-def[0].spec.geom->size[1]);
        bindpos.push_back(0);
        bindquat.push_back(1); bindquat.push_back(0);
        bindquat.push_back(0); bindquat.push_back(0);
      } else {
-        mjm_appendString(skin->bodyname, this_body);
+        mjs_appendString(skin->bodyname, this_body);
        bindpos.push_back((ix==count[0]-1) ? -2*def[0].spec.geom->size[0] : 0);
        bindpos.push_back(def[0].spec.geom->size[1]);
        bindpos.push_back(0);
@@ -1534,7 +1534,7 @@ void mjCComposite::MakeCableBones(mjCModel* model, mjmSkin* skin) {
-void mjCComposite::MakeCableBonesSubgrid(mjCModel* model, mjmSkin* skin) {
+void mjCComposite::MakeCableBonesSubgrid(mjCModel* model, mjsSkin* skin) {
  // populate bones
  for (int ix=0; ix<count[0]; ix++) {
    for (int iy=0; iy<count[1]; iy++) {
@@ -1563,7 +1563,7 @@ void mjCComposite::MakeCableBonesSubgrid(mjCModel* model, mjmSkin* skin) {
        bindpos.push_back(0);
        bindpos.push_back(0);
      }
-      mjm_appendString(skin->bodyname, txt);
+      mjs_appendString(skin->bodyname, txt);
      bindquat.push_back(1);
      bindquat.push_back(0);
      bindquat.push_back(0);
@@ -1888,10 +1888,10 @@ void mjCComposite::MakeSkin2Subgrid(mjCModel* model, mjtNum inflate) {
  // add skin, set name and material
  char txt[100];
-  mjmSkin* skin = mjm_addSkin(&model->spec);
+  mjsSkin* skin = mjs_addSkin(&model->spec);
  mju::sprintf_arr(txt, "%sSkin", prefix.c_str());
-  mjm_setString(skin->name, txt);
+  mjs_setString(skin->name, txt);
-  mjm_setString(skin->material, skinmaterial.c_str());
+  mjs_setString(skin->material, skinmaterial.c_str());
  mjuu_copyvec(skin->rgba, skinrgba, 4);
  skin->inflate = inflate;
  skin->group = skingroup;
@@ -2043,10 +2043,10 @@ void mjCComposite::MakeSkin3(mjCModel* model) {
  mju::sprintf_arr(cnt2, "%d", count[2]-1);
  // add skin, set name and material
-  mjmSkin* skin = mjm_addSkin(&model->spec);
+  mjsSkin* skin = mjs_addSkin(&model->spec);
  mju::sprintf_arr(txt, "%sSkin", prefix.c_str());
-  mjm_setString(skin->name, txt);
+  mjs_setString(skin->name, txt);
-  mjm_setString(skin->material, skinmaterial.c_str());
+  mjs_setString(skin->material, skinmaterial.c_str());
  mjuu_copyvec(skin->rgba, skinrgba, 4);
  skin->inflate = skininflate;
  skin->group = skingroup;
@@ -2191,7 +2191,7 @@ void mjCComposite::MakeSkin3(mjCModel* model) {
 // make one face of 3D skin, box
-void mjCComposite::MakeSkin3Box(mjmSkin* skin, int c0, int c1, int side,
+void mjCComposite::MakeSkin3Box(mjsSkin* skin, int c0, int c1, int side,
                                int& vcnt, const char* format) {
  char txt[100];
@@ -2224,7 +2224,7 @@ void mjCComposite::MakeSkin3Box(mjmSkin* skin, int c0, int c1, int side,
      mju::sprintf_arr(txt, format, prefix.c_str(), i0, i1);
      // bind pose: origin
-      mjm_appendString(skin->bodyname, txt);
+      mjs_appendString(skin->bodyname, txt);
      bindpos.push_back(0);
      bindpos.push_back(0);
      bindpos.push_back(0);
@@ -2246,7 +2246,7 @@ void mjCComposite::MakeSkin3Box(mjmSkin* skin, int c0, int c1, int side,
 // make one face of 3D skin, smooth
-void mjCComposite::MakeSkin3Smooth(mjmSkin* skin, int c0, int c1, int side,
+void mjCComposite::MakeSkin3Smooth(mjsSkin* skin, int c0, int c1, int side,
                                   const std::map<string, int>& vmap, const char* format) {
  char txt00[100], txt01[100], txt10[100], txt11[100];
@@ -2281,7 +2281,7 @@ void mjCComposite::MakeSkin3Smooth(mjmSkin* skin, int c0, int c1, int side,
      }
      // bind pose: origin
-      mjm_appendString(skin->bodyname, txt00);
+      mjs_appendString(skin->bodyname, txt00);
      bindpos.push_back(0);
      bindpos.push_back(0);
      bindpos.push_back(0);
@@ -69,25 +69,25 @@ class mjCComposite {
  bool AddDefaultJoint(char* error = NULL, int error_sz = 0);
  void AdjustSoft(mjtNum* solref, mjtNum* solimp, int level);
-  bool Make(mjSpec* spec, mjmBody* body, char* error, int error_sz);
+  bool Make(mjSpec* spec, mjsBody* body, char* error, int error_sz);
-  bool MakeParticle(mjCModel* model, mjmBody* body, char* error, int error_sz);
+  bool MakeParticle(mjCModel* model, mjsBody* body, char* error, int error_sz);
-  bool MakeGrid(mjCModel* model, mjmBody* body, char* error, int error_sz);
+  bool MakeGrid(mjCModel* model, mjsBody* body, char* error, int error_sz);
-  bool MakeRope(mjCModel* model, mjmBody* body, char* error, int error_sz);
+  bool MakeRope(mjCModel* model, mjsBody* body, char* error, int error_sz);
-  bool MakeCable(mjCModel* model, mjmBody* body, char* error, int error_sz);
+  bool MakeCable(mjCModel* model, mjsBody* body, char* error, int error_sz);
-  bool MakeBox(mjCModel* model, mjmBody* body, char* error, int error_sz);
+  bool MakeBox(mjCModel* model, mjsBody* body, char* error, int error_sz);
  void MakeShear(mjCModel* model);
  void MakeSkin2(mjCModel* model, mjtNum inflate);
  void MakeSkin2Subgrid(mjCModel* model, mjtNum inflate);
-  void MakeClothBones(mjCModel* model, mjmSkin* skin);
+  void MakeClothBones(mjCModel* model, mjsSkin* skin);
-  void MakeClothBonesSubgrid(mjCModel* model, mjmSkin* skin);
+  void MakeClothBonesSubgrid(mjCModel* model, mjsSkin* skin);
-  void MakeCableBones(mjCModel* model, mjmSkin* skin);
+  void MakeCableBones(mjCModel* model, mjsSkin* skin);
-  void MakeCableBonesSubgrid(mjCModel* model, mjmSkin* skin);
+  void MakeCableBonesSubgrid(mjCModel* model, mjsSkin* skin);
  void MakeSkin3(mjCModel* model);
-  void MakeSkin3Box(mjmSkin* skin, int c0, int c1, int side, int& vcnt, const char* format);
+  void MakeSkin3Box(mjsSkin* skin, int c0, int c1, int side, int& vcnt, const char* format);
-  void MakeSkin3Smooth(mjmSkin* skin, int c0, int c1, int side,
+  void MakeSkin3Smooth(mjsSkin* skin, int c0, int c1, int side,
                       const std::map<std::string, int>& vmap, const char* format);
  void BoxProject(double* pos);
@@ -116,7 +116,7 @@ class mjCComposite {
  // plugin support
  std::string plugin_name;
  std::string plugin_instance_name;
-  mjmPlugin plugin;
+  mjsPlugin plugin;
  // skin
  bool skin;                      // generate skin
@@ -136,11 +136,11 @@ class mjCComposite {
  int dim;                        // dimensionality
 private:
-  mjmBody* AddRopeBody(mjCModel* model, mjmBody* body, int ix, int ix1);
+  mjsBody* AddRopeBody(mjCModel* model, mjsBody* body, int ix, int ix1);
-  mjmBody* AddCableBody(mjCModel* model, mjmBody* body, int ix, mjtNum normal[3], mjtNum prev_quat[4]);
+  mjsBody* AddCableBody(mjCModel* model, mjsBody* body, int ix, mjtNum normal[3], mjtNum prev_quat[4]);
  // temporary skin vectors
-  void CopyIntoSkin(mjmSkin* skin);
+  void CopyIntoSkin(mjsSkin* skin);
  std::vector<int> face;
  std::vector<float> vert;
  std::vector<float> bindpos;
@@ -42,7 +42,7 @@ typedef enum _mjtFcompType {
 class mjCFlexcomp {
 public:
  mjCFlexcomp(void);
-  bool Make(mjSpec* spec, mjmBody* body, char* error, int error_sz);
+  bool Make(mjSpec* spec, mjsBody* body, char* error, int error_sz);
  bool MakeGrid(char* error, int error_sz);
  bool MakeBox(char* error, int error_sz);
@@ -50,6 +50,11 @@ class mjCFlexcomp {
  bool MakeMesh(mjCModel* model, char* error, int error_sz);
  bool MakeGMSH(mjCModel* model, char* error, int error_sz);
  void LoadGMSH(mjCModel* model, mjResource* resource);
  void LoadGMSH41(char* buffer, int binary, int nodeend, int nodebegin,
                  int elemend, int elembegin);
  void LoadGMSH22(char* buffer, int binary, int nodeend, int nodebegin,
                  int elemend, int elembegin);
  int GridID(int ix, int iy);
  int GridID(int ix, int iy, int iz);
@@ -79,7 +84,7 @@ class mjCFlexcomp {
  // pose transform relative to parent body
  double pos[3];                  // position
  double quat[4];                 // orientation
-  mjCAlternative alt;             // alternative orientation
+  mjsOrientation alt;             // alternative orientation
  // set by user or computed internally
  bool rigid;                     // all vertices are in parent body (all pinned)
@@ -93,7 +98,7 @@ class mjCFlexcomp {
  // plugin support
  std::string plugin_name;
  std::string plugin_instance_name;
-  mjmPlugin plugin;
+  mjsPlugin plugin;
 };
 #endif  // MUJOCO_SRC_USER_USER_FLEXCOMP_H_
@@ -22,7 +22,7 @@
 // default model attributes
-void mjm_defaultSpec(mjSpec& model) {
+void mjs_defaultSpec(mjSpec& model) {
  memset(&model, 0, sizeof(mjSpec));
  // default statistics
@@ -75,9 +75,16 @@ void mjm_defaultSpec(mjSpec& model) {
 // default orientation attributes
 void mjs_defaultOrientation(mjsOrientation& orient) {
  orient.axisangle[0] = orient.xyaxes[0] = orient.zaxis[0] = orient.euler[0] = mjNAN;
 }
 // default body attributes
-void mjm_defaultBody(mjmBody& body) {
+void mjs_defaultBody(mjsBody& body) {
-  memset(&body, 0, sizeof(mjmBody));
+  memset(&body, 0, sizeof(mjsBody));
  // body frame
  body.pos[0] = mjNAN;
@@ -94,8 +101,8 @@ void mjm_defaultBody(mjmBody& body) {
 // default frame attributes
-void mjm_defaultFrame(mjmFrame& frame) {
+void mjs_defaultFrame(mjsFrame& frame) {
-  memset(&frame, 0, sizeof(mjmFrame));
+  memset(&frame, 0, sizeof(mjsFrame));
  mju_zero3(frame.pos);
  mjuu_setvec(frame.quat, 1, 0, 0, 0);
  frame.alt.axisangle[0] = frame.alt.xyaxes[0] = frame.alt.zaxis[0] = frame.alt.euler[0] = mjNAN;
@@ -104,8 +111,8 @@ void mjm_defaultFrame(mjmFrame& frame) {
 // default joint attributes
-void mjm_defaultJoint(mjmJoint& joint) {
+void mjs_defaultJoint(mjsJoint& joint) {
-  memset(&joint, 0, sizeof(mjmJoint));
+  memset(&joint, 0, sizeof(mjsJoint));
  joint.type = mjJNT_HINGE;
  joint.axis[2] = 1;
@@ -119,8 +126,8 @@ void mjm_defaultJoint(mjmJoint& joint) {
 // default geom attributes
-void mjm_defaultGeom(mjmGeom& geom) {
+void mjs_defaultGeom(mjsGeom& geom) {
-  memset(&geom, 0, sizeof(mjmGeom));
+  memset(&geom, 0, sizeof(mjsGeom));
  // type
  geom.type = mjGEOM_SPHERE;
@@ -163,9 +170,9 @@ void mjm_defaultGeom(mjmGeom& geom) {
 // default site attributes
-void mjm_defaultSite(mjmSite& site) {
+void mjs_defaultSite(mjsSite& site) {
  // set everything to 0 / false / NULL
-  memset(&site, 0, sizeof(mjmSite));
+  memset(&site, 0, sizeof(mjsSite));
  // type
  site.type = mjGEOM_SPHERE;
@@ -184,8 +191,8 @@ void mjm_defaultSite(mjmSite& site) {
 // default cam attributes
-void mjm_defaultCamera(mjmCamera& cam) {
+void mjs_defaultCamera(mjsCamera& cam) {
-  memset(&cam, 0, sizeof(mjmCamera));
+  memset(&cam, 0, sizeof(mjsCamera));
  // type
  cam.mode = mjCAMLIGHT_FIXED;
@@ -203,8 +210,8 @@ void mjm_defaultCamera(mjmCamera& cam) {
 // default light attributes
-void mjm_defaultLight(mjmLight& light) {
+void mjs_defaultLight(mjsLight& light) {
-  memset(&light, 0, sizeof(mjmLight));
+  memset(&light, 0, sizeof(mjsLight));
  // mode
  light.mode = mjCAMLIGHT_FIXED;
@@ -223,8 +230,8 @@ void mjm_defaultLight(mjmLight& light) {
 // default flex attributes
-void mjm_defaultFlex(mjmFlex& flex) {
+void mjs_defaultFlex(mjsFlex& flex) {
-  memset(&flex, 0, sizeof(mjmFlex));
+  memset(&flex, 0, sizeof(mjsFlex));
  // set contact defaults
  flex.contype = 1;
@@ -247,8 +254,8 @@ void mjm_defaultFlex(mjmFlex& flex) {
 // default mesh attributes
-void mjm_defaultMesh(mjmMesh& mesh) {
+void mjs_defaultMesh(mjsMesh& mesh) {
-  memset(&mesh, 0, sizeof(mjmMesh));
+  memset(&mesh, 0, sizeof(mjsMesh));
  mjuu_setvec(mesh.refpos, 0, 0, 0);
  mjuu_setvec(mesh.refquat, 1, 0, 0, 0);
  mjuu_setvec(mesh.scale, 1, 1, 1);
@@ -258,15 +265,15 @@ void mjm_defaultMesh(mjmMesh& mesh) {
 // default height field attributes
-void mjm_defaultHField(mjmHField& hfield) {
+void mjs_defaultHField(mjsHField& hfield) {
-  memset(&hfield, 0, sizeof(mjmHField));
+  memset(&hfield, 0, sizeof(mjsHField));
 }
 // default skin attributes
-void mjm_defaultSkin(mjmSkin& skin) {
+void mjs_defaultSkin(mjsSkin& skin) {
-  memset(&skin, 0, sizeof(mjmSkin));
+  memset(&skin, 0, sizeof(mjsSkin));
  skin.rgba[0] = skin.rgba[1] = skin.rgba[2] = 0.5f;
  skin.rgba[3] = 1.0f;
  skin.inflate = 0;
@@ -276,8 +283,8 @@ void mjm_defaultSkin(mjmSkin& skin) {
 // default texture attributes
-void mjm_defaultTexture(mjmTexture& texture) {
+void mjs_defaultTexture(mjsTexture& texture) {
-  memset(&texture, 0, sizeof(mjmTexture));
+  memset(&texture, 0, sizeof(mjsTexture));
  texture.type = mjTEXTURE_CUBE;
  mjuu_setvec(texture.rgb1, 0.8, 0.8, 0.8);
  mjuu_setvec(texture.rgb2, 0.5, 0.5, 0.5);
@@ -290,8 +297,8 @@ void mjm_defaultTexture(mjmTexture& texture) {
 // default material attributes
-void mjm_defaultMaterial(mjmMaterial& material) {
+void mjs_defaultMaterial(mjsMaterial& material) {
-  memset(&material, 0, sizeof(mjmMaterial));
+  memset(&material, 0, sizeof(mjsMaterial));
  material.texuniform = false;
  material.texrepeat[0] = material.texrepeat[1] = 1;
  material.emission = 0;
@@ -304,8 +311,8 @@ void mjm_defaultMaterial(mjmMaterial& material) {
 // default pair attributes
-void mjm_defaultPair(mjmPair& pair) {
+void mjs_defaultPair(mjsPair& pair) {
-  memset(&pair, 0, sizeof(mjmPair));
+  memset(&pair, 0, sizeof(mjsPair));
  pair.condim = 3;
  mj_defaultSolRefImp(pair.solref, pair.solimp);
  pair.friction[0] = 1;
@@ -318,8 +325,8 @@ void mjm_defaultPair(mjmPair& pair) {
 // default equality attributes
-void mjm_defaultEquality(mjmEquality& equality) {
+void mjs_defaultEquality(mjsEquality& equality) {
-  memset(&equality, 0, sizeof(mjmEquality));
+  memset(&equality, 0, sizeof(mjsEquality));
  equality.type = mjEQ_CONNECT;
  equality.active = 1;
  mj_defaultSolRefImp(equality.solref, equality.solimp);
@@ -330,8 +337,8 @@ void mjm_defaultEquality(mjmEquality& equality) {
 // default tendon attributes
-void mjm_defaultTendon(mjmTendon& tendon) {
+void mjs_defaultTendon(mjsTendon& tendon) {
-  memset(&tendon, 0, sizeof(mjmTendon));
+  memset(&tendon, 0, sizeof(mjsTendon));
  tendon.limited = mjLIMITED_AUTO;
  tendon.springlength[0] = tendon.springlength[1] = -1;
  mj_defaultSolRefImp(tendon.solref_limit, tendon.solimp_limit);
@@ -344,8 +351,8 @@ void mjm_defaultTendon(mjmTendon& tendon) {
 // default actuator attributes
-void mjm_defaultActuator(mjmActuator& actuator) {
+void mjs_defaultActuator(mjsActuator& actuator) {
-  memset(&actuator, 0, sizeof(mjmActuator));
+  memset(&actuator, 0, sizeof(mjsActuator));
  // gain, bias
  actuator.gaintype = mjGAIN_FIXED;
@@ -370,8 +377,8 @@ void mjm_defaultActuator(mjmActuator& actuator) {
 // default sensor attributes
-void mjm_defaultSensor(mjmSensor& sensor) {
+void mjs_defaultSensor(mjsSensor& sensor) {
-  memset(&sensor, 0, sizeof(mjmSensor));
+  memset(&sensor, 0, sizeof(mjsSensor));
  sensor.type = mjSENS_TOUCH;
  sensor.datatype = mjDATATYPE_REAL;
  sensor.needstage = mjSTAGE_ACC;
@@ -380,36 +387,36 @@ void mjm_defaultSensor(mjmSensor& sensor) {
 // Default numeric attributes.
-void mjm_defaultNumeric(mjmNumeric& numeric) {
+void mjs_defaultNumeric(mjsNumeric& numeric) {
-  memset(&numeric, 0, sizeof(mjmNumeric));
+  memset(&numeric, 0, sizeof(mjsNumeric));
 }
 // Default text attributes.
-void mjm_defaultText(mjmText& text) {
+void mjs_defaultText(mjsText& text) {
-  memset(&text, 0, sizeof(mjmText));
+  memset(&text, 0, sizeof(mjsText));
 }
 // Default tuple attributes.
-void mjm_defaultTuple(mjmTuple& tuple) {
+void mjs_defaultTuple(mjsTuple& tuple) {
-  memset(&tuple, 0, sizeof(mjmTuple));
+  memset(&tuple, 0, sizeof(mjsTuple));
 }
 // Default keyframe attributes.
-void mjm_defaultKey(mjmKey& key) {
+void mjs_defaultKey(mjsKey& key) {
-  memset(&key, 0, sizeof(mjmKey));
+  memset(&key, 0, sizeof(mjsKey));
 }
 // default plugin attributes
-void mjm_defaultPlugin(mjmPlugin& plugin) {
+void mjs_defaultPlugin(mjsPlugin& plugin) {
-  memset(&plugin, 0, sizeof(mjmPlugin));
+  memset(&plugin, 0, sizeof(mjsPlugin));
  plugin.plugin_slot = -1;
 }
@@ -13,6 +13,7 @@
 // limitations under the License.
 #include <algorithm>
 #include <climits>
 #include <cmath>
 #include <csetjmp>
 #include <cstddef>
@@ -60,6 +61,7 @@
 #include "engine/engine_util_misc.h"
 #include "engine/engine_util_solve.h"
 #include "engine/engine_util_spatial.h"
 #include "user/user_cache.h"
 #include "user/user_model.h"
 #include "user/user_objects.h"
 #include "user/user_util.h"
@@ -129,7 +131,8 @@ static void ReadFromBuffer(T* dst, const char* src) {
 //------------------ class mjCMesh implementation --------------------------------------------------
 mjCMesh::mjCMesh(mjCModel* _model, mjCDef* _def) {
-  mjm_defaultMesh(spec);
+  mjs_defaultMesh(spec);
  elemtype = mjOBJ_MESH;
  // clear internal variables
  mjuu_setvec(pos_surface_, 0, 0, 0);
@@ -194,46 +197,67 @@ mjCMesh& mjCMesh::operator=(const mjCMesh& other) {
  if (this != &other) {
    this->spec = other.spec;
    *static_cast<mjCMesh_*>(this) = static_cast<const mjCMesh_&>(other);
-    *static_cast<mjmMesh*>(this) = static_cast<const mjmMesh&>(other);
+    *static_cast<mjsMesh*>(this) = static_cast<const mjsMesh&>(other);
    if (other.vert_) {
      size_t nvert = 3*other.nvert_*sizeof(float);
      this->vert_ = (float*)mju_malloc(nvert);
      memcpy(this->vert_, other.vert_, nvert);
    } else {
      this->vert_ = NULL;
    }
    if (other.normal_) {
      size_t nnormal = 3*other.nnormal_*sizeof(float);
      this->normal_ = (float*)mju_malloc(nnormal);
      memcpy(this->normal_, other.normal_, nnormal);
    } else {
      this->normal_ = NULL;
    }
    if (other.center_) {
      size_t ncenter = 3*other.nface_*sizeof(double);
      this->center_ = (double*)mju_malloc(ncenter);
      memcpy(this->center_, other.center_, ncenter);
    } else {
      this->center_ = NULL;
    }
    if (other.texcoord_) {
      size_t ntexcoord = 2*other.ntexcoord_*sizeof(float);
      this->texcoord_ = (float*)mju_malloc(ntexcoord);
      memcpy(this->texcoord_, other.texcoord_, ntexcoord);
    } else {
      this->texcoord_ = NULL;
    }
    if (other.face_) {
      size_t nface = 3*other.nface_*sizeof(int);
      this->face_ = (int*)mju_malloc(nface);
      memcpy(this->face_, other.face_, nface);
    } else {
      this->face_ = NULL;
    }
    if (other.facenormal_) {
      size_t nfacenormal = 3*other.nface_*sizeof(int);
      this->facenormal_ = (int*)mju_malloc(nfacenormal);
      memcpy(this->facenormal_, other.facenormal_, nfacenormal);
    } else {
      this->facenormal_ = NULL;
    }
    if (other.facetexcoord_) {
      size_t nfacetexcoord = 3*other.nface_*sizeof(int);
      this->facetexcoord_ = (int*)mju_malloc(nfacetexcoord);
      memcpy(this->facetexcoord_, other.facetexcoord_, nfacetexcoord);
    } else {
      this->facetexcoord_ = NULL;
    }
    if (other.graph_) {
      size_t szgraph = szgraph_*sizeof(int);
      this->graph_ = (int*)mju_malloc(szgraph);
      memcpy(this->graph_, other.graph_, szgraph);
    } else {
      this->graph_ = NULL;
    }
    if (other.plugin.instance) {
      mjCPlugin* new_plugin = new mjCPlugin(*static_cast<mjCPlugin*>(other.plugin.instance));
      plugin = new_plugin->spec;
      model->plugins.push_back(new_plugin);
    }
  }
  PointToLocal();
@@ -243,7 +267,7 @@ mjCMesh& mjCMesh::operator=(const mjCMesh& other) {
 void mjCMesh::PointToLocal() {
-  spec.element = (mjElement)this;
+  spec.element = static_cast<mjElement*>(this);
  spec.name = (mjString)&name;
  spec.classname = (mjString)&classname;
  spec.file = (mjString)&spec_file_;
@@ -260,7 +284,7 @@ void mjCMesh::PointToLocal() {
 void mjCMesh::CopyFromSpec() {
-  *static_cast<mjmMesh*>(this) = spec;
+  *static_cast<mjsMesh*>(this) = spec;
  file_ = spec_file_;
  content_type_ = spec_content_type_;
  uservert_ = spec_uservert_;
@@ -336,8 +360,9 @@ void mjCMesh::LoadSDF() {
                   name.c_str(), id);
  }
-  mjCPlugin* plugin_instance = (mjCPlugin*)plugin.instance;
+  mjCPlugin* plugin_instance = static_cast<mjCPlugin*>(plugin.instance);
  model->ResolvePlugin(this, plugin_name, plugin_instance_name, &plugin_instance);
  plugin.instance = plugin_instance;
  const mjpPlugin* pplugin = mjp_getPluginAtSlot(plugin_instance->spec.plugin_slot);
  if (!(pplugin->capabilityflags & mjPLUGIN_SDF)) {
    throw mjCError(this, "plugin '%s' does not support signed distance fields", pplugin->name);
@@ -410,6 +435,7 @@ void mjCMesh::LoadSDF() {
 // compiler
 void mjCMesh::Compile(const mjVFS* vfs) {
  CopyFromSpec();
  visual_ = true;
  // load file
  if (!file_.empty()) {
@@ -526,7 +552,8 @@ void mjCMesh::Compile(const mjVFS* vfs) {
    // check vertices exist
    for (int i=0; i<userface_.size(); i++) {
      if (userface_[i] >= nvert_ || userface_[i] < 0) {
-        throw mjCError(this, "index in face does not exist in vertex array");
+        throw mjCError(this, "in face %d, vertex index %d does not exist",
                       nullptr, i / 3, userface_[i]);
      }
    }
@@ -967,6 +994,19 @@ void mjCMesh::RemoveRepeated() {
 void mjCMesh::LoadOBJ(mjResource* resource) {
  tinyobj::ObjReader objReader;
  const void* bytes = nullptr;
  // try loading from cache
  mjCCache *cache = reinterpret_cast<mjCCache*>(mj_globalCache());
  if (cache) {
    auto asset = cache->Get(resource->name);
    if (asset.has_value() &&
        !mju_isModifiedResource(resource, asset->Timestamp().c_str())) {
      if (LoadCachedOBJ(asset.value())) {
        return;
      }
    }
  }
  int buffer_sz = mju_readResource(resource, &bytes);
  if (buffer_sz < 0) {
    throw mjCError(this, "could not read OBJ file '%s'", resource->name);
@@ -1030,9 +1070,117 @@ void mjCMesh::LoadOBJ(mjResource* resource) {
  for (int i=0; i<usertexcoord_.size()/2; i++) {
    usertexcoord_[2*i+1] = 1-usertexcoord_[2*i+1];
  }
  // try caching asset
  if (cache) {
    mjCAsset asset("", resource->name, resource->timestamp);
    asset.AddVector("uservert_", uservert_);
    asset.AddVector("usernormal_", usernormal_);
    asset.AddVector("usertexcoord_", usertexcoord_);
    if (!objReader.GetShapes().empty()) {
      const auto& mesh = objReader.GetShapes()[0].mesh;
      std::vector<int> vertex_index;
      vertex_index.reserve(mesh.indices.size());
      std::vector<int> normal_index;
      normal_index.reserve(mesh.indices.size());
      std::vector<int> texcoord_index;
      texcoord_index.reserve(mesh.indices.size());
      for (tinyobj::index_t index : mesh.indices) {
        vertex_index.push_back(index.vertex_index);
        normal_index.push_back(index.normal_index);
        texcoord_index.push_back(index.texcoord_index);
      }
      asset.AddVector("num_face_vertices", mesh.num_face_vertices);
      asset.AddVector("vertex_index", vertex_index);
      asset.AddVector("normal_index", normal_index);
      asset.AddVector("texcoord_index", texcoord_index);
    } else {
      asset.AddVector("num_face_vertices", std::vector<unsigned char>());
      asset.AddVector("vertex_index", std::vector<int>());
      asset.AddVector("normal_index", std::vector<int>());
      asset.AddVector("texcoord_index", std::vector<int>());
    }
    cache->Insert(std::move(asset));
  }
 }
 // load OBJ from cached asset, return true on success
 bool mjCMesh::LoadCachedOBJ(const mjCAsset& asset) {
  // check that asset has all data
  if (!asset.HasData("uservert_") || !asset.HasData("usernormal_")
      || !asset.HasData("usertexcoord_") || !asset.HasData("num_face_vertices")
      || !asset.HasData("vertex_index") || !asset.HasData("normal_index")
      || !asset.HasData("texcoord_index")) {
    return false;
  }
  uservert_ = asset.GetVector<float>("uservert_").value();
  usernormal_ = asset.GetVector<float>("usernormal_").value();
  usertexcoord_ = asset.GetVector<float>("usertexcoord_").value();
  vector<int> vertex_index = asset.GetVector<int>("vertex_index").value();
  vector<int> normal_index = asset.GetVector<int>("normal_index").value();
  vector<int> texcoord_index = asset.GetVector<int>("texcoord_index").value();
  vector<unsigned char> num_face_vertices =
      asset.GetVector<unsigned char>("num_face_vertices").value();
  bool righthand = (scale[0] * scale[1] * scale[2]) > 0;
  for (int face = 0, i = 0; i < vertex_index.size();) {
    int nfacevert = num_face_vertices[face];
    if (nfacevert < 3 || nfacevert > 4) {
      throw mjCError(
          this, "only tri or quad meshes are supported for OBJ (file '%s')",
          asset.Id().c_str());
    }
    userface_.push_back(vertex_index[i]);
    userface_.push_back(vertex_index[i + (righthand == 1 ? 1 : 2)]);
    userface_.push_back(vertex_index[i + (righthand == 1 ? 2 : 1)]);
    if (!usernormal_.empty()) {
      userfacenormal_.push_back(normal_index[i]);
      userfacenormal_.push_back(normal_index[i + (righthand == 1 ? 1 : 2)]);
      userfacenormal_.push_back(normal_index[i + (righthand == 1 ? 2 : 1)]);
    }
    if (!usertexcoord_.empty()) {
      userfacetexcoord_.push_back(texcoord_index[i]);
      userfacetexcoord_.push_back(texcoord_index[i + (righthand == 1 ? 1 : 2)]);
      userfacetexcoord_.push_back(texcoord_index[i + (righthand == 1 ? 2 : 1)]);
    }
    if (nfacevert == 4) {
      userface_.push_back(vertex_index[i]);
      userface_.push_back(vertex_index[i + (righthand == 1 ? 2 : 3)]);
      userface_.push_back(vertex_index[i + (righthand == 1 ? 3 : 2)]);
      if (!usernormal_.empty()) {
        userfacenormal_.push_back(normal_index[i]);
        userfacenormal_.push_back(normal_index[i + (righthand == 1 ? 1 : 2)]);
        userfacenormal_.push_back(normal_index[i + (righthand == 1 ? 2 : 1)]);
      }
      if (!usertexcoord_.empty()) {
        userfacetexcoord_.push_back(texcoord_index[i]);
        userfacetexcoord_.push_back(texcoord_index[i + (righthand == 1 ? 1 : 2)]);
        userfacetexcoord_.push_back(texcoord_index[i + (righthand == 1 ? 2 : 1)]);
      }
    }
    i += nfacevert;
    ++face;
  }
  return true;
 }
 // load STL binary mesh
 void mjCMesh::LoadSTL(mjResource* resource) {
  bool righthand = (scale[0]*scale[1]*scale[2]>0);
@@ -1146,6 +1294,12 @@ void mjCMesh::LoadMSH(mjResource* resource) {
    throw mjCError(this, "invalid sizes in MSH file '%s'", resource->name);
  }
  if (nvert_ >= INT_MAX / sizeof(float) / 3 ||
      nnormal_ >= INT_MAX / sizeof(float) / 3 ||
      ntexcoord_ >= INT_MAX / sizeof(float) / 2 ||
      nface_ >= INT_MAX / sizeof(int) / 3) {
    throw mjCError(this, "too large sizes in MSH file '%s'.", resource->name);
  }
  // check file size
  if (buffer_sz != 4*sizeof(int) + 3*nvert_*sizeof(float) + 3*nnormal_*sizeof(float) +
      2*ntexcoord_*sizeof(float) + 3*nface_*sizeof(int)) {
@@ -1493,7 +1647,7 @@ void mjCMesh::CheckMesh(mjtGeomInertia type) {
  if (!processed_) {
    return;
  }
-  if (invalidorientation_.first>=0 || invalidorientation_.second>=0)
+  if ((invalidorientation_.first>=0 || invalidorientation_.second>=0) && model->exactmeshinertia)
    throw mjCError(this,
                   "faces of mesh '%s' have inconsistent orientation. Please check the "
                   "faces containing the vertices %d and %d.",
@@ -1910,7 +2064,8 @@ void mjCMesh::MakeCenter(void) {
 // constructor
 mjCSkin::mjCSkin(mjCModel* _model) {
-  mjm_defaultSkin(spec);
+  mjs_defaultSkin(spec);
  elemtype = mjOBJ_SKIN;
  // set model pointer
  model = _model;
@@ -1939,8 +2094,26 @@ mjCSkin::mjCSkin(mjCModel* _model) {
 mjCSkin::mjCSkin(const mjCSkin& other) {
  *this = other;
 }
 mjCSkin& mjCSkin::operator=(const mjCSkin& other) {
  if (this != &other) {
    this->spec = other.spec;
    *static_cast<mjCSkin_*>(this) = static_cast<const mjCSkin_&>(other);
    *static_cast<mjsSkin*>(this) = static_cast<const mjsSkin&>(other);
  }
  PointToLocal();
  return *this;
 }
 void mjCSkin::PointToLocal() {
-  spec.element = (mjElement)this;
+  spec.element = static_cast<mjElement*>(this);
  spec.name = (mjString)&name;
  spec.classname = (mjString)&classname;
  spec.file = (mjString)&spec_file_;
@@ -1958,8 +2131,16 @@ void mjCSkin::PointToLocal() {
 void mjCSkin::NameSpace(const mjCModel* m) {
  for (int i=0; i<(int)spec_bodyname_.size(); i++) {
    spec_bodyname_[i] = m->prefix + spec_bodyname_[i] + m->suffix;
  }
 }
 void mjCSkin::CopyFromSpec() {
-  *static_cast<mjmSkin*>(this) = spec;
+  *static_cast<mjsSkin*>(this) = spec;
  file_ = spec_file_;
  material_ = spec_material_;
  vert_ = spec_vert_;
@@ -2001,6 +2182,20 @@ mjCSkin::~mjCSkin() {
 void mjCSkin::ResolveReferences(const mjCModel* m) {
  size_t nbone = bodyname_.size();
  bodyid.resize(nbone);
  for (int i=0; i<nbone; i++) {
    mjCBase* pbody = m->FindObject(mjOBJ_BODY, bodyname_[i]);
    if (!pbody) {
      throw mjCError(this, "unknown body '%s' in skin", bodyname_[i].c_str());
    }
    bodyid[i] = pbody->id;
  }
 }
 // compiler
 void mjCSkin::Compile(const mjVFS* vfs) {
  CopyFromSpec();
@@ -2081,14 +2276,7 @@ void mjCSkin::Compile(const mjVFS* vfs) {
  }
  // resolve body names
-  bodyid.resize(nbone);
+  ResolveReferences(model);
  for (int i=0; i<nbone; i++) {
    mjCBase* pbody = model->FindObject(mjOBJ_BODY, bodyname_[i]);
    if (!pbody) {
      throw mjCError(this, "unknown body '%s' in skin", bodyname_[i].c_str());
    }
    bodyid[i] = pbody->id;
  }
  // resolve material name
  mjCBase* pmat = model->FindObject(mjOBJ_MATERIAL, material_);
@@ -2301,7 +2489,8 @@ constexpr int eledge[3][6][2] = {{{ 0,  1}, {-1, -1}, {-1, -1},
 // constructor
 mjCFlex::mjCFlex(mjCModel* _model) {
-  mjm_defaultFlex(spec);
+  mjs_defaultFlex(spec);
  elemtype = mjOBJ_FLEX;
  // set model
  model = _model;
@@ -2328,7 +2517,7 @@ mjCFlex& mjCFlex::operator=(const mjCFlex& other) {
  if (this != &other) {
    this->spec = other.spec;
    *static_cast<mjCFlex_*>(this) = static_cast<const mjCFlex_&>(other);
-    *static_cast<mjmFlex*>(this) = static_cast<const mjmFlex&>(other);
+    *static_cast<mjsFlex*>(this) = static_cast<const mjsFlex&>(other);
  }
  PointToLocal();
  return *this;
@@ -2336,7 +2525,7 @@ mjCFlex& mjCFlex::operator=(const mjCFlex& other) {
 void mjCFlex::PointToLocal() {
-  spec.element = (mjElement)this;
+  spec.element = static_cast<mjElement*>(this);
  spec.name = (mjString)&name;
  spec.classname = (mjString)&classname;
  spec.material = (mjString)&spec_material_;
@@ -2348,8 +2537,17 @@ void mjCFlex::PointToLocal() {
 }
 void mjCFlex::NameSpace(const mjCModel* m) {
  for (int i=0; i<(int)spec_vertbody_.size(); i++) {
    spec_vertbody_[i] = m->prefix + spec_vertbody_[i] + m->suffix;
  }
 }
 void mjCFlex::CopyFromSpec() {
-  *static_cast<mjmFlex*>(this) = spec;
+  *static_cast<mjsFlex*>(this) = spec;
  spec.info = (mjString)&info;
  material_ = spec_material_;
  vertbody_ = spec_vertbody_;
@@ -2380,6 +2578,18 @@ void mjCFlex::DelTexcoord() {
 }
 void mjCFlex::ResolveReferences(const mjCModel* m) {
  for (int i=0; i<(int)vertbody_.size(); i++) {
    mjCBase* pbody = m->FindObject(mjOBJ_BODY, vertbody_[i]);
    if (pbody) {
      vertbodyid.push_back(pbody->id);
    } else {
        throw mjCError(this, "unkown body '%s' in flex", vertbody_[i].c_str());
    }
  }
 }
 // compiler
 void mjCFlex::Compile(const mjVFS* vfs) {
  CopyFromSpec();
@@ -2441,14 +2651,7 @@ void mjCFlex::Compile(const mjVFS* vfs) {
  }
  // resolve body ids
-  for (int i=0; i<(int)vertbody_.size(); i++) {
+  ResolveReferences(model);
    mjCBase* pbody = model->FindObject(mjOBJ_BODY, vertbody_[i]);
    if (pbody) {
      vertbodyid.push_back(pbody->id);
    } else {
        throw mjCError(this, "unkown body '%s' in flex", vertbody_[i].c_str());
    }
  }
  // process elements
  for (int e=0; e<(int)elem_.size()/(dim+1); e++) {
@@ -2564,7 +2767,8 @@ void mjCFlex::Compile(const mjVFS* vfs) {
  for (int i=0; i<(int)vertbodyid.size(); i++) {
    if (model->bodies[vertbodyid[i]]->plugin.instance) {
-      mjCPlugin* plugin_instance = (mjCPlugin*)model->bodies[vertbodyid[i]]->plugin.instance;
+      mjCPlugin* plugin_instance =
          static_cast<mjCPlugin*>(model->bodies[vertbodyid[i]]->plugin.instance);
      plugin_instance->config_attribs["face"] = userface;
      plugin_instance->config_attribs["edge"] = useredge;
    }
@@ -83,7 +83,8 @@ static void copyvec(T1* dest, T2* src, int n) {
 // constructor
 mjCModel::mjCModel() {
-  mjm_defaultSpec(spec);
+  mjs_defaultSpec(spec);
  elemtype = mjOBJ_UNKNOWN;
  spec_comment_.clear();
  spec_modelfiledir_.clear();
  spec_meshdir_.clear();
@@ -120,6 +121,8 @@ mjCModel::mjCModel() {
  tuples.clear();
  keys.clear();
  defaults.clear();
  prefix = "";
  suffix = "";
  Clear();
  //------------------------ master default set
@@ -138,6 +141,152 @@ mjCModel::mjCModel() {
  world->def = defaults[0];
  bodies.push_back(world);
  // create mjCBase lists from children lists
  CreateObjectLists();
  // point to model from spec
  PointToLocal();
  // this class allocated the plugins
  plugin_owner = true;
 }
 mjCModel::mjCModel(const mjCModel& other) {
  *this = other;
 }
 mjCModel& mjCModel::operator=(const mjCModel& other) {
  if (this != &other) {
    plugin_owner = false;
    this->spec = other.spec;
    *static_cast<mjCModel_*>(this) = static_cast<const mjCModel_&>(other);
    *static_cast<mjSpec*>(this) = static_cast<const mjSpec&>(other);
    // the world copy constructor takes care of copying the tree
    mjCBody* world = new mjCBody(*other.bodies[0], this);
    bodies.push_back(world);
    // add everything else
    *this += other;
    // copy name maps
    for (int i=0; i<mjNOBJECT; i++) {
      ids[i] = other.ids[i];
    }
  }
  return *this;
 }
 // copy vector of elements from another model to this model
 template <class T>
 void mjCModel::CopyList(std::vector<T*>& dest,
                        const std::vector<T*>& source,
                        std::map<mjCDef*, int>& def_map,
                        const std::vector<mjCDef*>& defaults) {
  // loop over the elements from the other model
  for (T* element : source) {
    try {
      // try to find the referenced object in this model
      element->NameSpace(element->model);
      element->CopyFromSpec();
      element->ResolveReferences(this);
    } catch (mjCError err) {
      // if not present, skip the element
      continue;
    }
    // copy the element from the other model to this model
    dest.push_back(new T(*element));
    dest.back()->model = this;
    dest.back()->def = defaults[def_map[element->def]];
  }
 }
 mjCModel& mjCModel::operator+=(const mjCModel& other) {
  if (this != &other) {
    // create global lists
    MakeLists(bodies[0]);
    CreateObjectLists();
    ProcessLists();
    // copy all elements not in the tree
    std::map<mjCDef*, int> def_map;
    for (int i = 0; i < other.defaults.size(); i++) {
      defaults.push_back(new mjCDef(*other.defaults[i]));
      def_map[other.defaults[i]] = i;
    }
    CopyList(flexes, other.flexes, def_map, defaults);
    CopyList(meshes, other.meshes, def_map, defaults);
    CopyList(skins, other.skins, def_map, defaults);
    CopyList(hfields, other.hfields, def_map, defaults);
    CopyList(textures, other.textures, def_map, defaults);
    CopyList(materials, other.materials, def_map, defaults);
    CopyList(pairs, other.pairs, def_map, defaults);
    CopyList(excludes, other.excludes, def_map, defaults);
    CopyList(tendons, other.tendons, def_map, defaults);
    CopyList(equalities, other.equalities, def_map, defaults);
    CopyList(actuators, other.actuators, def_map, defaults);
    CopyList(sensors, other.sensors, def_map, defaults);
    CopyList(numerics, other.numerics, def_map, defaults);
    CopyList(texts, other.texts, def_map, defaults);
    CopyList(tuples, other.tuples, def_map, defaults);
    CopyList(keys, other.keys, def_map, defaults);
    // plugins are global
    plugins = other.plugins;
    active_plugins = other.active_plugins;
    // update defaults for the copied objects
    for (int i = 1; i < other.bodies.size(); i++) {
      bodies[i]->def = defaults[def_map[other.bodies[i]->def]];
    }
    for (int i = 0; i < other.joints.size(); i++) {
      joints[i]->def = defaults[def_map[other.joints[i]->def]];
    }
    for (int i = 0; i < other.geoms.size(); i++) {
      geoms[i]->def = defaults[def_map[other.geoms[i]->def]];
    }
    for (int i = 0; i < other.sites.size(); i++) {
      sites[i]->def = defaults[def_map[other.sites[i]->def]];
    }
    for (int i = 0; i < other.cameras.size(); i++) {
      cameras[i]->def = defaults[def_map[other.cameras[i]->def]];
    }
    for (int i = 0; i < other.lights.size(); i++) {
      lights[i]->def = defaults[def_map[other.lights[i]->def]];
    }
    // cast children to mjCBase
    // restore to the same state as other
    if (!compiled) {
      mjCBody* world = bodies[0];
      bodies.clear();
      frames.clear();
      joints.clear();
      geoms.clear();
      sites.clear();
      cameras.clear();
      lights.clear();
      bodies.push_back(world);
    }
  }
  PointToLocal();
  return *this;
 }
 // TODO: we should not use C-type casting with multiple C++ inheritance
 void mjCModel::CreateObjectLists() {
  for (int i = 0; i < mjNOBJECT; ++i) {
    object_lists[i] = nullptr;
  }
@@ -166,23 +315,12 @@ mjCModel::mjCModel() {
  object_lists[mjOBJ_TUPLE]    = (std::vector<mjCBase*>*) &tuples;
  object_lists[mjOBJ_KEY]      = (std::vector<mjCBase*>*) &keys;
  object_lists[mjOBJ_PLUGIN]   = (std::vector<mjCBase*>*) &plugins;
  // point to model from spec
  PointToLocal();
 }
 mjCModel::mjCModel(const mjCModel& other) {
  *this = other;
  PointToLocal();
 }
 void mjCModel::PointToLocal() {
-  spec.element = (mjElement)this;
+  spec.element = static_cast<mjElement*>(this);
  spec.comment = (mjString)&spec_comment_;
  spec.modelfiledir = (mjString)&spec_modelfiledir_;
  spec.modelname = (mjString)&spec_modelname_;
@@ -230,9 +368,12 @@ mjCModel::~mjCModel() {
  for (int i=0; i<texts.size(); i++) delete texts[i];
  for (int i=0; i<tuples.size(); i++) delete tuples[i];
  for (int i=0; i<keys.size(); i++) delete keys[i];
  for (int i=0; i<plugins.size(); i++) delete plugins[i];
  for (int i=0; i<defaults.size(); i++) delete defaults[i];
  if (plugin_owner) {
    for (int i=0; i<plugins.size(); i++) delete plugins[i];
  }
  // clear pointer lists created in model construction
  flexes.clear();
  meshes.clear();
@@ -339,7 +480,6 @@ void mjCModel::Clear(void) {
  hasImplicitPluginElem = false;
  compiled = false;
  errInfo = mjCError();
  fixCount = 0;
  qpos0.clear();
 }
@@ -498,35 +638,28 @@ mjCBase* mjCModel::GetObject(mjtObj type, int id) {
 //------------------------ API FOR ACCESS TO PRIVATE VARIABLES -------------------------------------
 // compiled flag
-bool mjCModel::IsCompiled(void) {
+bool mjCModel::IsCompiled(void) const {
  return compiled;
 }
 // number of massless bodies that were fixed
 int mjCModel::GetFixed(void) {
  return fixCount;
 }
 // get reference of error object
-const mjCError& mjCModel::GetError(void) {
+const mjCError& mjCModel::GetError(void) const {
  return errInfo;
 }
 // pointer to world body
-mjCBody* mjCModel::GetWorld(void) {
+mjCBody* mjCModel::GetWorld(void) const {
  return bodies[0];
 }
 // find default class name in array
-mjCDef* mjCModel::FindDef(string name) {
+mjCDef* mjCModel::FindDef(string name) const {
  for (int i=0; i<(int)defaults.size(); i++) {
    if (defaults[i]->name==name) {
      return defaults[i];
@@ -589,7 +722,7 @@ static T* findobject(std::string_view name, const vector<T*>& list, const mjKeyM
 }
 // find object in global lists given string type and name
-mjCBase* mjCModel::FindObject(mjtObj type, string name) {
+mjCBase* mjCModel::FindObject(mjtObj type, string name) const {
  if (!object_lists[type]) {
    return nullptr;
  }
@@ -598,8 +731,46 @@ mjCBase* mjCModel::FindObject(mjtObj type, string name) {
 // find body by name
 mjCBody* mjCModel::FindBody(mjCBody* body, std::string name) const {
  if (body->name == name) {
    return body;
  }
  for (auto child : body->bodies) {
    auto candidate = FindBody(child, name);
    if (candidate) {
      return candidate;
    }
  }
  return nullptr;
 }
 // find frame by name
 mjCFrame* mjCModel::FindFrame(mjCBody* body, std::string name) const{
  for (auto frame : body->frames) {
    if (frame->name == name) {
      return frame;
    }
  }
  for (auto body : body->bodies) {
    auto candidate = FindFrame(body, name);
    if (candidate) {
      return candidate;
    }
  }
  return nullptr;
 }
 // detect null pose
-bool mjCModel::IsNullPose(const mjtNum* pos, const mjtNum* quat) {
+bool mjCModel::IsNullPose(const mjtNum* pos, const mjtNum* quat) const {
  bool result = true;
  // check position if given
@@ -761,112 +932,154 @@ void mjCModel::DeleteAll<mjCTexture>(std::vector<mjCTexture*>& elements) {
  elements.clear();
 }
 // set nuser fields
 void mjCModel::SetNuser(){
  if (nuser_body == -1) {
    nuser_body = 0;
    for (int i=0; i<bodies.size(); i++) {
      nuser_body = mjMAX(nuser_body, bodies[i]->spec_userdata_.size());
    }
  }
  if (nuser_jnt == -1) {
    nuser_jnt = 0;
    for (int i=0; i<joints.size(); i++) {
      nuser_jnt = mjMAX(nuser_jnt, joints[i]->spec_userdata_.size());
    }
  }
  if (nuser_geom == -1) {
    nuser_geom = 0;
    for (int i=0; i<geoms.size(); i++) {
      nuser_geom = mjMAX(nuser_geom, geoms[i]->spec_userdata_.size());
    }
  }
  if (nuser_site == -1) {
    nuser_site = 0;
    for (int i=0; i<sites.size(); i++) {
      nuser_site = mjMAX(nuser_site, sites[i]->spec_userdata_.size());
    }
  }
  if (nuser_cam == -1) {
    nuser_cam = 0;
    for (int i=0; i<cameras.size(); i++) {
      nuser_cam = mjMAX(nuser_cam, cameras[i]->spec_userdata_.size());
    }
  }
  if (nuser_tendon == -1) {
    nuser_tendon = 0;
    for (int i=0; i<tendons.size(); i++) {
      nuser_tendon = mjMAX(nuser_tendon, tendons[i]->spec_userdata_.size());
    }
  }
  if (nuser_actuator == -1) {
    nuser_actuator = 0;
    for (int i=0; i<actuators.size(); i++) {
      nuser_actuator = mjMAX(nuser_actuator, actuators[i]->spec_userdata_.size());
    }
  }
  if (nuser_sensor == -1) {
    nuser_sensor = 0;
    for (int i=0; i<sensors.size(); i++) {
      nuser_sensor = mjMAX(nuser_sensor, sensors[i]->spec_userdata_.size());
    }
  }
 }
 // index assets
 void mjCModel::IndexAssets(bool discard) {
  // assets referenced in geoms
  for (int i=0; i<geoms.size(); i++) {
-    mjCGeom* pgeom = geoms[i];
+    mjCGeom* geom = geoms[i];
    // find material by name
-    if (!pgeom->get_material().empty()) {
+    if (!geom->get_material().empty()) {
-      mjCBase* m = FindObject(mjOBJ_MATERIAL, pgeom->get_material());
+      mjCBase* material = FindObject(mjOBJ_MATERIAL, geom->get_material());
-      if (m) {
+      if (material) {
-        pgeom->matid = m->id;
+        geom->matid = material->id;
      } else {
-        throw mjCError(pgeom, "material '%s' not found in geom %d", pgeom->get_material().c_str(), i);
+        throw mjCError(geom, "material '%s' not found in geom %d", geom->get_material().c_str(), i);
      }
    }
    // find mesh by name
-    if (!pgeom->get_meshname().empty()) {
+    if (!geom->get_meshname().empty()) {
-      mjCBase* m = FindObject(mjOBJ_MESH, pgeom->get_meshname());
+      mjCBase* mesh = FindObject(mjOBJ_MESH, geom->get_meshname());
-      if (m) {
+      if (mesh) {
-        if (discard && geoms[i]->visual_) {
+        if (!geom->visual_) {
-          // do not associate with a mesh
+          ((mjCMesh*)mesh)->SetNotVisual();  // reset to true by mesh->Compile()
          pgeom->mesh = nullptr;
        } else {
          // associate mesh with geom
          pgeom->mesh = (mjCMesh*)m;
          // mark mesh as not visual
          // this is irreversible so only performed when IndexAssets is called with discard
          if (discard) {
            pgeom->mesh->SetNotVisual();
          }
        }
        geom->mesh = (discard && geom->visual_) ? nullptr : (mjCMesh*)mesh;
      } else {
-        throw mjCError(pgeom, "mesh '%s' not found in geom %d", pgeom->get_meshname().c_str(), i);
+        throw mjCError(geom, "mesh '%s' not found in geom %d", geom->get_meshname().c_str(), i);
      }
    }
    // find hfield by name
-    if (!pgeom->get_hfieldname().empty()) {
+    if (!geom->get_hfieldname().empty()) {
-      mjCBase* m = FindObject(mjOBJ_HFIELD, pgeom->get_hfieldname());
+      mjCBase* hfield = FindObject(mjOBJ_HFIELD, geom->get_hfieldname());
-      if (m) {
+      if (hfield) {
-        pgeom->hfield = (mjCHField*)m;
+        geom->hfield = (mjCHField*)hfield;
      } else {
-        throw mjCError(pgeom, "hfield '%s' not found in geom %d", pgeom->get_hfieldname().c_str(), i);
+        throw mjCError(geom, "hfield '%s' not found in geom %d", geom->get_hfieldname().c_str(), i);
      }
    }
  }
  // assets referenced in skins
  for (int i=0; i<skins.size(); i++) {
-    mjCSkin* pskin = skins[i];
+    mjCSkin* skin = skins[i];
    // find material by name
-    if (!pskin->material_.empty()) {
+    if (!skin->material_.empty()) {
-      mjCBase* m = FindObject(mjOBJ_MATERIAL, pskin->material_);
+      mjCBase* material = FindObject(mjOBJ_MATERIAL, skin->material_);
-      if (m) {
+      if (material) {
-        pskin->matid = m->id;
+        skin->matid = material->id;
      } else {
-        throw mjCError(pskin, "material '%s' not found in skin %d", pskin->material_.c_str(), i);
+        throw mjCError(skin, "material '%s' not found in skin %d", skin->material_.c_str(), i);
      }
    }
  }
  // materials referenced in sites
  for (int i=0; i<sites.size(); i++) {
-    mjCSite* psite = sites[i];
+    mjCSite* site = sites[i];
    // find material by name
-    if (!psite->material_.empty()) {
+    if (!site->material_.empty()) {
-      mjCBase* m = FindObject(mjOBJ_MATERIAL, psite->get_material());
+      mjCBase* material = FindObject(mjOBJ_MATERIAL, site->get_material());
-      if (m) {
+      if (material) {
-        psite->matid = m->id;
+        site->matid = material->id;
      } else {
-        throw mjCError(psite, "material '%s' not found in site %d", psite->material_.c_str(), i);
+        throw mjCError(site, "material '%s' not found in site %d", site->material_.c_str(), i);
      }
    }
  }
  // materials referenced in tendons
  for (int i=0; i<tendons.size(); i++) {
-    mjCTendon* pten = tendons[i];
+    mjCTendon* tendon = tendons[i];
    // find material by name
-    if (!pten->material_.empty()) {
+    if (!tendon->material_.empty()) {
-      mjCBase* m = FindObject(mjOBJ_MATERIAL, pten->material_);
+      mjCBase* material = FindObject(mjOBJ_MATERIAL, tendon->material_);
-      if (m) {
+      if (material) {
-        pten->matid = m->id;
+        tendon->matid = material->id;
      } else {
-        throw mjCError(pten, "material '%s' not found in tendon %d", pten->material_.c_str(), i);
+        throw mjCError(tendon, "material '%s' not found in tendon %d", tendon->material_.c_str(), i);
      }
    }
  }
  // textures referenced in materials
  for (int i=0; i<materials.size(); i++) {
-    mjCMaterial* pmat = materials[i];
+    mjCMaterial* material = materials[i];
    // find texture by name
-    if (!pmat->texture_.empty()) {
+    if (!material->texture_.empty()) {
-      mjCBase* m = FindObject(mjOBJ_TEXTURE, pmat->texture_);
+      mjCBase* texture = FindObject(mjOBJ_TEXTURE, material->texture_);
-      if (m) {
+      if (texture) {
-        pmat->texid = m->id;
+        material->texid = texture->id;
      } else {
-        throw mjCError(pmat, "texture '%s' not found in material %d", pmat->texture_.c_str(), i);
+        throw mjCError(material, "texture '%s' not found in material %d", material->texture_.c_str(), i);
      }
    }
  }
@@ -1331,7 +1544,7 @@ static int namelist(vector<T*>& list, int adr, int* name_adr, char* names, int*
      continue;
    }
-    uint64_t j = mj_hashdjb2(list[i]->name.c_str(), map_size);
+    uint64_t j = mj_hashString(list[i]->name.c_str(), map_size);
    // find first empty slot using linear probing
    for (; map[j]!=-1; j=(j+1) % map_size) {}
@@ -1555,6 +1768,7 @@ void mjCModel::CopyTree(mjModel* m) {
      m->jnt_group[jid] = pj->group;
      m->jnt_limited[jid] = (mjtByte)pj->is_limited();
      m->jnt_actfrclimited[jid] = (mjtByte)pj->is_actfrclimited();
      m->jnt_actgravcomp[jid] = pj->actgravcomp;
      m->jnt_qposadr[jid] = qposadr;
      m->jnt_dofadr[jid] = dofadr;
      m->jnt_bodyid[jid] = pj->body->id;
@@ -2144,7 +2358,7 @@ void mjCModel::CopyObjects(mjModel* m) {
    m->hfield_adr[i] = data_adr;
    // copy elevation data
-    memcpy(m->hfield_data + data_adr, phf->data, phf->nrow*phf->ncol*sizeof(float));
+    memcpy(m->hfield_data + data_adr, phf->data.data(), phf->nrow*phf->ncol*sizeof(float));
    // advance counter
    data_adr += phf->nrow*phf->ncol;
@@ -2163,7 +2377,7 @@ void mjCModel::CopyObjects(mjModel* m) {
    m->tex_adr[i] = data_adr;
    // copy rgb data
-    memcpy(m->tex_rgb + data_adr, ptex->rgb, 3*ptex->width*ptex->height);
+    memcpy(m->tex_rgb + data_adr, ptex->rgb.data(), 3*ptex->width*ptex->height);
    // advance counter
    data_adr += 3*ptex->width*ptex->height;
@@ -2719,6 +2933,21 @@ static void processlist(mjListKeyMap& ids, vector<T*>& list,
 }
 // set object ids, check for repeated names
 void mjCModel::ProcessLists() {
  for (int i = 0; i < mjNOBJECT; i++) {
    if (i != mjOBJ_XBODY && object_lists[i]) {
      processlist(ids, *object_lists[i], (mjtObj) i);
    }
  }
  // check repeated names in meta elements
  processlist(ids, frames, mjOBJ_FRAME);
 }
 // error handler for low-level engine
 static thread_local std::jmp_buf error_jmp_buf;
 static thread_local char errortext[500] = "";
@@ -2852,14 +3081,7 @@ void mjCModel::TryCompile(mjModel*& m, mjData*& d, const mjVFS* vfs) {
  CheckEmptyNames();
  // set object ids, check for repeated names
-  for (int i = 0; i < mjNOBJECT; i++) {
+  ProcessLists();
    if (i != mjOBJ_XBODY && object_lists[i]) {
      processlist(ids, *object_lists[i], (mjtObj) i);
    }
  }
  // check repeated names in meta elements
  processlist(ids, frames, mjOBJ_FRAME);
  // delete visual assets
  if (discardvisual) {
@@ -2869,8 +3091,8 @@ void mjCModel::TryCompile(mjModel*& m, mjData*& d, const mjVFS* vfs) {
    DeleteAll(textures);
  }
-  // convert names into indices
+  // map names to asset references
-  IndexAssets(false);
+  IndexAssets(/*discard=*/false);
  // mark meshes that need convex hull
  for (int i=0; i<geoms.size(); i++) {
@@ -2880,61 +3102,14 @@ void mjCModel::TryCompile(mjModel*& m, mjData*& d, const mjVFS* vfs) {
    }
  }
  // automatically set nuser fields
  SetNuser();
  // compile meshes (needed for geom compilation)
  for (int i=0; i<meshes.size(); i++) {
    meshes[i]->Compile(vfs);
  }
  // automatically set nuser fields
  if (nuser_body == -1) {
    nuser_body = 0;
    for (int i=0; i<bodies.size(); i++) {
      nuser_body = mjMAX(nuser_body, bodies[i]->spec_userdata_.size());
    }
  }
  if (nuser_jnt == -1) {
    nuser_jnt = 0;
    for (int i=0; i<joints.size(); i++) {
      nuser_jnt = mjMAX(nuser_jnt, joints[i]->spec_userdata_.size());
    }
  }
  if (nuser_geom == -1) {
    nuser_geom = 0;
    for (int i=0; i<geoms.size(); i++) {
      nuser_geom = mjMAX(nuser_geom, geoms[i]->spec_userdata_.size());
    }
  }
  if (nuser_site == -1) {
    nuser_site = 0;
    for (int i=0; i<sites.size(); i++) {
      nuser_site = mjMAX(nuser_site, sites[i]->spec_userdata_.size());
    }
  }
  if (nuser_cam == -1) {
    nuser_cam = 0;
    for (int i=0; i<cameras.size(); i++) {
      nuser_cam = mjMAX(nuser_cam, cameras[i]->spec_userdata_.size());
    }
  }
  if (nuser_tendon == -1) {
    nuser_tendon = 0;
    for (int i=0; i<tendons.size(); i++) {
      nuser_tendon = mjMAX(nuser_tendon, tendons[i]->spec_userdata_.size());
    }
  }
  if (nuser_actuator == -1) {
    nuser_actuator = 0;
    for (int i=0; i<actuators.size(); i++) {
      nuser_actuator = mjMAX(nuser_actuator, actuators[i]->spec_userdata_.size());
    }
  }
  if (nuser_sensor == -1) {
    nuser_sensor = 0;
    for (int i=0; i<sensors.size(); i++) {
      nuser_sensor = mjMAX(nuser_sensor, sensors[i]->spec_userdata_.size());
    }
  }
  // compile objects in kinematic tree
  for (int i=0; i<bodies.size(); i++) {
    bodies[i]->Compile();  // also compiles joints, geoms, sites, cameras, lights
@@ -3057,7 +3232,7 @@ void mjCModel::TryCompile(mjModel*& m, mjData*& d, const mjVFS* vfs) {
    std::vector<std::vector<int>> plugin_to_actuators(nplugin);
    for (int i = 0; i < nu; ++i) {
      if (actuators[i]->plugin.active) {
-        int actuator_plugin = ((mjCPlugin*)actuators[i]->plugin.instance)->id;
+        int actuator_plugin = static_cast<mjCPlugin*>(actuators[i]->plugin.instance)->id;
        m->actuator_plugin[i] = actuator_plugin;
        plugin_to_actuators[actuator_plugin].push_back(i);
      } else {
@@ -3067,7 +3242,7 @@ void mjCModel::TryCompile(mjModel*& m, mjData*& d, const mjVFS* vfs) {
    for (int i = 0; i < nbody; ++i) {
      if (bodies[i]->plugin.active) {
-        m->body_plugin[i] = ((mjCPlugin*)bodies[i]->plugin.instance)->id;
+        m->body_plugin[i] = static_cast<mjCPlugin*>(bodies[i]->plugin.instance)->id;
      } else {
        m->body_plugin[i] = -1;
      }
@@ -3075,7 +3250,7 @@ void mjCModel::TryCompile(mjModel*& m, mjData*& d, const mjVFS* vfs) {
    for (int i = 0; i < ngeom; ++i) {
      if (geoms[i]->plugin.active) {
-        m->geom_plugin[i] = ((mjCPlugin*)geoms[i]->plugin.instance)->id;
+        m->geom_plugin[i] = static_cast<mjCPlugin*>(geoms[i]->plugin.instance)->id;
      } else {
        m->geom_plugin[i] = -1;
      }
@@ -3084,7 +3259,7 @@ void mjCModel::TryCompile(mjModel*& m, mjData*& d, const mjVFS* vfs) {
    std::vector<std::vector<int>> plugin_to_sensors(nplugin);
    for (int i = 0; i < nsensor; ++i) {
      if (sensors[i]->type == mjSENS_PLUGIN) {
-        int sensor_plugin = ((mjCPlugin*)sensors[i]->plugin.instance)->id;
+        int sensor_plugin = static_cast<mjCPlugin*>(sensors[i]->plugin.instance)->id;
        m->sensor_plugin[i] = sensor_plugin;
        plugin_to_sensors[sensor_plugin].push_back(i);
      } else {
@@ -33,133 +33,14 @@
 typedef std::map<std::string, int, std::less<> > mjKeyMap;
 typedef std::array<mjKeyMap, mjNOBJECT> mjListKeyMap;
-// mjCModel contains everything needed to generate the low-level model.
+class mjCModel_ : public mjElement {
 // It can be constructed manually by calling 'Add' functions and setting
 // the public fields of the various objects.  Alternatively it can constructed
 // by loading an XML file via mjCXML.  Once an mjCModel object is
 // constructed, 'Compile' can be called to generate the corresponding mjModel object
 // (which is the low-level model).  The mjCModel object can then be deleted.
 class mjCModel : private mjSpec {
  friend class mjCBody;
  friend class mjCCamera;
  friend class mjCGeom;
  friend class mjCFlex;
  friend class mjCHField;
  friend class mjCFrame;
  friend class mjCJoint;
  friend class mjCEquality;
  friend class mjCMesh;
  friend class mjCSkin;
  friend class mjCSite;
  friend class mjCTendon;
  friend class mjCTexture;
  friend class mjCActuator;
  friend class mjCSensor;
  friend class mjCDef;
  friend class mjXReader;
  friend class mjXWriter;
 public:
-  mjCModel();
+  // attach namespaces
-  mjCModel(const mjCModel& other);
+  std::string prefix;
-  ~mjCModel();
+  std::string suffix;
  void CopyFromSpec();  // copy spec to private attributes
  void PointToLocal();
-  mjSpec spec;
+ protected:
-
+  bool compiled;      // already compiled flag
  mjModel* Compile(const mjVFS* vfs = nullptr);  // construct mjModel
  bool CopyBack(const mjModel*);                 // DECOMPILER: copy numeric back
  void FuseStatic();                             // fuse static bodies with parent
  void FuseReindex(mjCBody* body);               // reindex elements during fuse
  // API for adding model elements
  mjCFlex* AddFlex();
  mjCMesh* AddMesh(mjCDef* def = nullptr);
  mjCSkin* AddSkin();
  mjCHField* AddHField();
  mjCTexture* AddTexture();
  mjCMaterial* AddMaterial(mjCDef* def = nullptr);
  mjCPair* AddPair(mjCDef* def = nullptr);          // geom pair for inclusion
  mjCBodyPair* AddExclude();                        // body pair for exclusion
  mjCEquality* AddEquality(mjCDef* def = nullptr);  // equality constraint
  mjCTendon* AddTendon(mjCDef* def = nullptr);
  mjCActuator* AddActuator(mjCDef* def = nullptr);
  mjCSensor* AddSensor();
  mjCNumeric* AddNumeric();
  mjCText* AddText();
  mjCTuple* AddTuple();
  mjCKey* AddKey();
  mjCPlugin* AddPlugin();
  // delete elements marked as discard=true
  template <class T> void Delete(std::vector<T*>& elements,
                                 const std::vector<bool>& discard);
  // delete all elements
  template <class T> void DeleteAll(std::vector<T*>& elements);
  // API for access to model elements (outside tree)
  int NumObjects(mjtObj type);              // number of objects in specified list
  mjCBase* GetObject(mjtObj type, int id);  // pointer to specified object
  // API for access to other variables
  bool IsCompiled();                                       // is model already compiled
  int GetFixed();                                          // number of fixed massless bodies
  const mjCError& GetError(void);                          // get reference of error object
  mjCBody* GetWorld();                                     // pointer to world body
  mjCDef* FindDef(std::string name);                       // find default class name
  mjCDef* AddDef(std::string name, int parentid);          // add default class to array
  mjCBase* FindObject(mjtObj type, std::string name);      // find object given type and name
  bool IsNullPose(const mjtNum* pos, const mjtNum* quat);  // detect null pose
  // accessors
  std::string get_meshdir(void) const { return meshdir_; }
  std::string get_texturedir(void) const { return texturedir_; }
  // resolve plugin instance, create a new one if needed
  void ResolvePlugin(mjCBase* obj, const std::string& plugin_name,
                     const std::string& plugin_instance_name,
                     mjCPlugin** plugin_instance);
  // settings for each defaults class
  std::vector<mjCDef*> defaults;
  // list of active plugins
  std::vector<std::pair<const mjpPlugin*, int>> active_plugins;
 private:
  void TryCompile(mjModel*& m, mjData*& d, const mjVFS* vfs);
  mjModel* _Compile(const mjVFS* vfs);
  // clear objects allocated by Compile
  void Clear(void);
  // add object of any type
  template <class T> T* AddObject(std::vector<T*>& list, std::string type);
  // add object of any type, with def parameter
  template <class T> T* AddObjectDef(std::vector<T*>& list, std::string type,
                                     mjCDef* def);
  // if asset name is missing, set to filename
  template<class T> void SetDefaultNames(std::vector<T*>& assets);
  // delete material from object
  template <class T> void DeleteMaterial(std::vector<T*>& list,
                                         std::string_view name = "");
  // compile phases
  void MakeLists(mjCBody* body);        // make lists of bodies, geoms, joints, sites
  void IndexAssets(bool discard);       // convert asset names into indices
  void CheckEmptyNames();               // check empty names
  void SetSizes();                      // compute sizes
  void AutoSpringDamper(mjModel*);      // automatic stiffness and damping computation
  void LengthRange(mjModel*, mjData*);  // compute actuator lengthrange
  void CopyNames(mjModel*);             // copy names, compute name addresses
  void CopyPaths(mjModel*);             // copy paths, compute path addresses
  void CopyObjects(mjModel*);           // copy objects outside kinematic tree
  void CopyTree(mjModel*);              // copy objects inside kinematic tree
  // sizes set from object list lengths
  int nbody;     // number of bodies
@@ -224,6 +105,168 @@ class mjCModel : private mjSpec {
  int nD;              // number of non-zeros in sparse dof-dof matrix
  int nB;              // number of non-zeros in sparse body-dof matrix
  // statistics, as computed by mj_setConst
  double meaninertia_auto;  // mean diagonal inertia, as computed by mj_setConst
  double meanmass_auto;     // mean body mass, as computed by mj_setConst
  double meansize_auto;     // mean body size, as computed by mj_setConst
  double extent_auto;       // spatial extent, as computed by mj_setConst
  double center_auto[3];    // center of model, as computed by mj_setConst
  // save qpos0, to recognize changed key_qpos in write
  std::vector<mjtNum> qpos0;
  // variable-size attributes
  std::string comment_;           // comment at top of XML
  std::string modelfiledir_;      // path to model file
  std::string modelname_;
  std::string meshdir_;
  std::string texturedir_;
  std::string spec_comment_;
  std::string spec_modelfiledir_;
  std::string spec_modelname_;
  std::string spec_meshdir_;
  std::string spec_texturedir_;
 };
 // mjCModel contains everything needed to generate the low-level model.
 // It can be constructed manually by calling 'Add' functions and setting
 // the public fields of the various objects.  Alternatively it can constructed
 // by loading an XML file via mjCXML.  Once an mjCModel object is
 // constructed, 'Compile' can be called to generate the corresponding mjModel object
 // (which is the low-level model).  The mjCModel object can then be deleted.
 class mjCModel : public mjCModel_, private mjSpec {
  friend class mjCBase;
  friend class mjCBody;
  friend class mjCCamera;
  friend class mjCGeom;
  friend class mjCFlex;
  friend class mjCHField;
  friend class mjCFrame;
  friend class mjCJoint;
  friend class mjCEquality;
  friend class mjCMesh;
  friend class mjCSkin;
  friend class mjCSite;
  friend class mjCTendon;
  friend class mjCTexture;
  friend class mjCActuator;
  friend class mjCSensor;
  friend class mjCDef;
  friend class mjXReader;
  friend class mjXWriter;
 public:
  mjCModel();
  mjCModel(const mjCModel& other);
  mjCModel& operator=(const mjCModel& other);
  mjCModel& operator+=(const mjCModel& other);
  ~mjCModel();
  void CopyFromSpec();  // copy spec to private attributes
  void PointToLocal();
  mjSpec spec;
  mjModel* Compile(const mjVFS* vfs = nullptr);  // construct mjModel
  bool CopyBack(const mjModel*);                 // DECOMPILER: copy numeric back
  void FuseStatic();                             // fuse static bodies with parent
  void FuseReindex(mjCBody* body);               // reindex elements during fuse
  // API for adding model elements
  mjCFlex* AddFlex();
  mjCMesh* AddMesh(mjCDef* def = nullptr);
  mjCSkin* AddSkin();
  mjCHField* AddHField();
  mjCTexture* AddTexture();
  mjCMaterial* AddMaterial(mjCDef* def = nullptr);
  mjCPair* AddPair(mjCDef* def = nullptr);          // geom pair for inclusion
  mjCBodyPair* AddExclude();                        // body pair for exclusion
  mjCEquality* AddEquality(mjCDef* def = nullptr);  // equality constraint
  mjCTendon* AddTendon(mjCDef* def = nullptr);
  mjCActuator* AddActuator(mjCDef* def = nullptr);
  mjCSensor* AddSensor();
  mjCNumeric* AddNumeric();
  mjCText* AddText();
  mjCTuple* AddTuple();
  mjCKey* AddKey();
  mjCPlugin* AddPlugin();
  // copy vector of elements to this model
  template <class T> void CopyList(std::vector<T*>& dest,
                                   const std::vector<T*>& source,
                                   std::map<mjCDef*, int>& def_map,
                                   const std::vector<mjCDef*>& defaults);
  // delete elements marked as discard=true
  template <class T> void Delete(std::vector<T*>& elements,
                                 const std::vector<bool>& discard);
  // delete all elements
  template <class T> void DeleteAll(std::vector<T*>& elements);
  // API for access to model elements (outside tree)
  int NumObjects(mjtObj type);              // number of objects in specified list
  mjCBase* GetObject(mjtObj type, int id);  // pointer to specified object
  // API for access to other variables
  bool IsCompiled() const;                                       // is model already compiled
  const mjCError& GetError(void) const;                          // get reference of error object
  mjCBody* GetWorld() const;                                     // pointer to world body
  mjCDef* FindDef(std::string name) const;                       // find default class name
  mjCDef* AddDef(std::string name, int parentid);                // add default class to array
  mjCBase* FindObject(mjtObj type, std::string name) const;      // find object given type and name
  mjCBody* FindBody(mjCBody* body, std::string name) const;      // find body given name
  mjCFrame* FindFrame(mjCBody* body, std::string name) const;    // find frame given name
  bool IsNullPose(const mjtNum* pos, const mjtNum* quat) const;  // detect null pose
  // accessors
  std::string get_meshdir(void) const { return meshdir_; }
  std::string get_texturedir(void) const { return texturedir_; }
  // resolve plugin instance, create a new one if needed
  void ResolvePlugin(mjCBase* obj, const std::string& plugin_name,
                     const std::string& plugin_instance_name,
                     mjCPlugin** plugin_instance);
  // settings for each defaults class
  std::vector<mjCDef*> defaults;
  // list of active plugins
  std::vector<std::pair<const mjpPlugin*, int>> active_plugins;
 private:
  void TryCompile(mjModel*& m, mjData*& d, const mjVFS* vfs);
  mjModel* _Compile(const mjVFS* vfs);
  // clear objects allocated by Compile
  void Clear(void);
  // add object of any type
  template <class T> T* AddObject(std::vector<T*>& list, std::string type);
  // add object of any type, with def parameter
  template <class T> T* AddObjectDef(std::vector<T*>& list, std::string type,
                                     mjCDef* def);
  // if asset name is missing, set to filename
  template<class T> void SetDefaultNames(std::vector<T*>& assets);
  // delete material from object
  template <class T> void DeleteMaterial(std::vector<T*>& list,
                                         std::string_view name = "");
  // compile phases
  void MakeLists(mjCBody* body);        // make lists of bodies, geoms, joints, sites
  void SetNuser();                      // set nuser fields
  void IndexAssets(bool discard);       // convert asset names into indices
  void CheckEmptyNames();               // check empty names
  void SetSizes();                      // compute sizes
  void AutoSpringDamper(mjModel*);      // automatic stiffness and damping computation
  void LengthRange(mjModel*, mjData*);  // compute actuator lengthrange
  void CopyNames(mjModel*);             // copy names, compute name addresses
  void CopyPaths(mjModel*);             // copy paths, compute path addresses
  void CopyObjects(mjModel*);           // copy objects outside kinematic tree
  void CopyTree(mjModel*);              // copy objects inside kinematic tree
  // objects created here
  std::vector<mjCFlex*>     flexes;      // list of flexes
  std::vector<mjCMesh*>     meshes;      // list of meshes
@@ -255,32 +298,14 @@ class mjCModel : private mjSpec {
  // array of pointers to each object list (enumerated by type)
  std::array<std::vector<mjCBase*>*, mjNOBJECT> object_lists;
-  // statistics, as computed by mj_setConst
+  // create mjCBase lists from children lists
-  double meaninertia_auto;  // mean diagonal inertia, as computed by mj_setConst
+  void CreateObjectLists();
  double meanmass_auto;     // mean body mass, as computed by mj_setConst
  double meansize_auto;     // mean body size, as computed by mj_setConst
  double extent_auto;       // spatial extent, as computed by mj_setConst
  double center_auto[3];    // center of model, as computed by mj_setConst
  // populate objects ids
  void ProcessLists();
  mjListKeyMap ids;   // map from object names to ids
  bool compiled;      // already compiled flag (cannot be compiled again)
  mjCError errInfo;   // last error info
-  int fixCount;       // how many bodies have been fixed
+  bool plugin_owner;  // this class allocated the plugins
  // save qpos0, to recognize changed key_qpos in write
  std::vector<mjtNum> qpos0;
  // variable-size attributes
  std::string comment_;           // comment at top of XML
  std::string modelfiledir_;      // path to model file
  std::string modelname_;
  std::string meshdir_;
  std::string texturedir_;
  std::string spec_comment_;
  std::string spec_modelfiledir_;
  std::string spec_modelname_;
  std::string spec_meshdir_;
  std::string spec_texturedir_;
 };
 #endif  // MUJOCO_SRC_USER_USER_MODEL_H_
@@ -15,10 +15,8 @@
 #ifndef MUJOCO_SRC_USER_USER_OBJECTS_H_
 #define MUJOCO_SRC_USER_USER_OBJECTS_H_
 #include <array>
 #include <functional>
 #include <map>
 #include <optional>
 #include <string>
 #include <string_view>
 #include <utility>
@@ -28,10 +26,10 @@
 #include <mujoco/mjmodel.h>
 #include <mujoco/mjplugin.h>
 #include "user/user_api.h"
 #include "user/user_cache.h"
 // forward declarations of all mjC/X classes
 class mjCError;
 class mjCAlternative;
 class mjCBase;
 class mjCBody;
 class mjCFrame;
@@ -83,13 +81,10 @@ class [[nodiscard]] mjCError {
 // alternative specifications of frame orientation
-class mjCAlternative : public mjmOrientation {
+const char* ResolveOrientation(double* quat,             // set frame quat
- public:
+                               bool degree,              // angle format: degree/radian
-  mjCAlternative();                               // constuctor
+                               const char* sequence,     // euler sequence format: "xyz"
-  const char* Set(double* quat,                   // set frame quat
+                               const mjsOrientation& orient);
                  bool degree,                    // angle format: degree/radian
                  const char* sequence);          // euler sequence format: "xyz"
 };
@@ -144,7 +139,27 @@ class mjCBoundingVolumeHierarchy : public mjCBoundingVolumeHierarchy_ {
  mjCBoundingVolume* GetBoundingVolume(int id);
 private:
-  int MakeBVH(std::vector<const mjCBoundingVolume*>& elements, int lev = 0);
+  // internal class used during BVH construction, for partial sorting of bounding volumes
  struct BVElement {
    const mjCBoundingVolume* e;
    // position of the element in the BVH axes
    mjtNum lpos[3];
  };
  struct BVElementCompare {
    int axis = 0;
    bool operator()(const BVElement& e1, const BVElement& e2) const {
      if (e1.lpos[axis] != e2.lpos[axis]) {
        return e1.lpos[axis] < e2.lpos[axis];
      }
      // comparing pointers gives a stable sort, because they both come from the same array
      return e1.e < e2.e;
    }
  };
  int MakeBVH(std::vector<BVElement>::iterator elements_begin,
              std::vector<BVElement>::iterator elements_end, int lev = 0);
 };
@@ -152,13 +167,14 @@ class mjCBoundingVolumeHierarchy : public mjCBoundingVolumeHierarchy_ {
 //------------------------- class mjCBase ----------------------------------------------------------
 // Generic functionality for all derived classes
-class mjCBase_ {
+class mjCBase_ : public mjElement {
 public:
-  std::string name;               // object name
+  int id;                 // object id
-  std::string classname;          // defaults class name
+  std::string name;       // object name
-  int id;                         // object id
+  std::string classname;  // defaults class name
-  std::string info;               // error message info set by the user
+  std::string info;       // error message info set by the user
-  mjCModel* model;                // pointer to model that created object
+  std::string prefix;     // prefix for model operations
  std::string suffix;     // suffix for model operations
 };
 class mjCBase : public mjCBase_ {
@@ -178,11 +194,18 @@ class mjCBase : public mjCBase_ {
  // Copy spec into private attributes
  virtual void CopyFromSpec() {}
  // Throws an error if any of the references is missing
  virtual void ResolveReferences(const mjCModel* m) {}
  // Appends prefix and suffix to reference
  virtual void NameSpace(const mjCModel* m) {}
  // Copy assignment
  mjCBase& operator=(const mjCBase& other);
  mjCDef* def;                    // defaults class used to init this object
  mjCFrame* frame;                // pointer to frame transformation
  mjCModel* model;                // pointer to model that created object
 protected:
  mjCBase();                                 // constructor
@@ -196,10 +219,6 @@ class mjCBase : public mjCBase_ {
 // Describes a rigid body
 class mjCBody_ : public mjCBase {
 public:
  mjCAlternative alt_;
  mjCAlternative ialt_;
 protected:
  // variables computed by 'Compile' and 'AddXXX'
  int parentid;                   // parent index in global array
@@ -226,12 +245,13 @@ class mjCBody_ : public mjCBase {
  std::vector<double> spec_userdata_;
 };
-class mjCBody : public mjCBody_, private mjmBody {
+class mjCBody : public mjCBody_, private mjsBody {
  friend class mjCJoint;
  friend class mjCGeom;
  friend class mjCSite;
  friend class mjCCamera;
  friend class mjCComposite;
  friend class mjCFrame;
  friend class mjCLight;
  friend class mjCFlex;
  friend class mjCFlexcomp;
@@ -253,11 +273,17 @@ class mjCBody : public mjCBody_, private mjmBody {
  mjCCamera*  AddCamera(mjCDef* = 0);
  mjCLight*   AddLight(mjCDef* = 0);
  // API for adding existing objects to body
  mjCBody& operator+=(mjCBody& other);
  // API for accessing objects
  int NumObjects(mjtObj type);
  mjCBase* GetObject(mjtObj type, int id);
  mjCBase* FindObject(mjtObj type, std::string name, bool recursive = true);
  // Propagate suffix and prefix to the whole tree
  void NameSpace(const mjCModel* m);
  // set explicitinertial to true
  void MakeInertialExplicit();
@@ -266,7 +292,7 @@ class mjCBody : public mjCBody_, private mjmBody {
  const char* FullInertia(double quat[4], double inertia[3]);
  // variables set by user
-  mjmBody spec;
+  mjsBody spec;
  // inherited
  using mjCBase::name;
@@ -277,10 +303,10 @@ class mjCBody : public mjCBody_, private mjmBody {
  const std::vector<double>& get_userdata() { return userdata_; }
 private:
-  mjCBody(mjCModel*);                        // constructor
+  mjCBody(mjCModel*);                               // constructor
-  mjCBody(const mjCBody& other);             // copy constructor
+  mjCBody(const mjCBody& other, mjCModel* _model);  // copy constructor
-  mjCBody& operator=(const mjCBody& other);  // copy assignment
+  mjCBody& operator=(const mjCBody& other);         // copy assignment
-  ~mjCBody();                                // destructor
+  ~mjCBody();                                       // destructor
  void Compile(void);             // compiler
  void GeomFrame(void);           // get inertial info from geoms
@@ -306,10 +332,9 @@ class mjCBody : public mjCBody_, private mjmBody {
 class mjCFrame_ : public mjCBase {
 protected:
  bool compiled;                           // frame already compiled
  mjCAlternative alt_;
 };
-class mjCFrame : public mjCFrame_, private mjmFrame {
+class mjCFrame : public mjCFrame_, private mjsFrame {
  friend class mjCBase;
  friend class mjCBody;
  friend class mjCGeom;
@@ -320,19 +345,25 @@ class mjCFrame : public mjCFrame_, private mjmFrame {
  friend class mjCModel;
 public:
-  mjmFrame spec;
+  mjsFrame spec;
  using mjCBase::name;
  using mjCBase::classname;
  using mjCBase::info;
  void CopyFromSpec(void);
  void PointToLocal(void);
  void SetParent(mjCBody* _body);
  mjCFrame& operator+=(const mjCBody& other);
  mjCFrame& operator+=(const mjCFrame& other);
 private:
  mjCFrame(mjCModel* = 0, mjCFrame* = 0);      // constructor
  mjCFrame(const mjCFrame& other);             // copy constructor
  mjCFrame& operator=(const mjCFrame& other);  // copy assignment
  void Compile(void);                          // compiler
  mjCBody* body;  // body that owns the frame
 };
@@ -349,7 +380,7 @@ class mjCJoint_ : public mjCBase {
  std::vector<double> spec_userdata_;
 };
-class mjCJoint : public mjCJoint_, private mjmJoint {
+class mjCJoint : public mjCJoint_, private mjsJoint {
  friend class mjCDef;
  friend class mjCEquality;
  friend class mjCBody;
@@ -359,7 +390,7 @@ class mjCJoint : public mjCJoint_, private mjmJoint {
  friend class mjXURDF;
 public:
-  mjmJoint spec;
+  mjsJoint spec;
  using mjCBase::name;
  using mjCBase::classname;
  using mjCBase::info;
@@ -393,7 +424,6 @@ class mjCGeom_ : public mjCBase {
  bool inferinertia;           // true if inertia should be computed from geom
 protected:
  mjCAlternative alt_;
  bool visual_;                       // true: geom does not collide and is unreferenced
  int matid;                          // id of geom's material
  mjCMesh* mesh;                      // geom's mesh
@@ -417,7 +447,7 @@ class mjCGeom_ : public mjCBase {
  std::vector<double> spec_userdata_;
 };
-class mjCGeom : public mjCGeom_, private mjmGeom {
+class mjCGeom : public mjCGeom_, private mjsGeom {
  friend class mjCDef;
  friend class mjCMesh;
  friend class mjCPair;
@@ -429,7 +459,7 @@ class mjCGeom : public mjCGeom_, private mjmGeom {
 public:
  using mjCBase::name;
-  mjmGeom spec;                       // variables set by user
+  mjsGeom spec;                       // variables set by user
  double GetVolume(void);             // compute geom volume
  void SetInertia(void);              // compute and set geom inertia
  bool IsVisual(void) const { return visual_; }
@@ -473,8 +503,6 @@ class mjCGeom : public mjCGeom_, private mjmGeom {
 class mjCSite_ : public mjCBase {
 protected:
  mjCAlternative alt_;
  // variable-size data
  std::string material_;
  std::vector<double> userdata_;
@@ -486,7 +514,7 @@ class mjCSite_ : public mjCBase {
  int matid;                      // material id for rendering
 };
-class mjCSite : public mjCSite_, private mjmSite {
+class mjCSite : public mjCSite_, private mjsSite {
  friend class mjCDef;
  friend class mjCBody;
  friend class mjCModel;
@@ -494,9 +522,9 @@ class mjCSite : public mjCSite_, private mjmSite {
  friend class mjXURDF;
 public:
-  mjmSite spec;                   // variables set by user
+  mjsSite spec;                   // variables set by user
-  // use strings from mjCBase rather than mjStrings from mjmSite
+  // use strings from mjCBase rather than mjStrings from mjsSite
  using mjCBase::name;
  using mjCBase::classname;
  using mjCBase::info;
@@ -525,14 +553,13 @@ class mjCCamera_ : public mjCBase {
 protected:
  mjCBody* body;                  // camera's body
  int targetbodyid;               // id of target body; -1: none
  mjCAlternative alt_;
  std::string targetbody_;
  std::string spec_targetbody_;
  std::vector<double> userdata_;
  std::vector<double> spec_userdata_;
 };
-class mjCCamera : public mjCCamera_, private mjmCamera {
+class mjCCamera : public mjCCamera_, private mjsCamera {
  friend class mjCDef;
  friend class mjCBody;
  friend class mjCModel;
@@ -540,7 +567,7 @@ class mjCCamera : public mjCCamera_, private mjmCamera {
  friend class mjXWriter;
 public:
-  mjmCamera spec;
+  mjsCamera spec;
  using mjCBase::name;
  using mjCBase::classname;
  using mjCBase::info;
@@ -572,14 +599,14 @@ class mjCLight_ : public mjCBase {
  std::string spec_targetbody_;
 };
-class mjCLight : public mjCLight_, private mjmLight {
+class mjCLight : public mjCLight_, private mjsLight {
  friend class mjCDef;
  friend class mjCBody;
  friend class mjCModel;
  friend class mjXWriter;
 public:
-  mjmLight spec;
+  mjsLight spec;
  using mjCBase::name;
  using mjCBase::classname;
  using mjCBase::info;
@@ -633,7 +660,7 @@ class mjCFlex_ : public mjCBase {
  std::vector<float> spec_texcoord_;
 };
-class mjCFlex: public mjCFlex_, private mjmFlex {
+class mjCFlex: public mjCFlex_, private mjsFlex {
  friend class mjCDef;
  friend class mjCModel;
  friend class mjCFlexcomp;
@@ -641,13 +668,15 @@ class mjCFlex: public mjCFlex_, private mjmFlex {
  friend class mjXWriter;
 public:
-  mjmFlex spec;
+  mjsFlex spec;
  using mjCBase::name;
  using mjCBase::classname;
  using mjCBase::info;
  void CopyFromSpec(void);
  void PointToLocal(void);
  void ResolveReferences(const mjCModel* m);
  void NameSpace(const mjCModel* m);
  // used by mjXWriter and mjCModel
  const std::string& get_material() { return material_; }
@@ -735,7 +764,8 @@ class mjCMesh_ : public mjCBase {
  std::vector<double> face_aabb_;     // bounding boxes of all faces
 };
-class mjCMesh: public mjCMesh_, private mjmMesh {
+class mjCMesh: public mjCMesh_, private mjsMesh {
  friend class mjCModel;
  friend class mjCFlexcomp;
  friend class mjXWriter;
 public:
@@ -744,7 +774,7 @@ class mjCMesh: public mjCMesh_, private mjmMesh {
  mjCMesh& operator=(const mjCMesh& other);  // copy assignment
  ~mjCMesh();
-  mjmMesh spec;
+  mjsMesh spec;
  using mjCBase::name;
  using mjCBase::classname;
  using mjCBase::info;
@@ -808,6 +838,7 @@ class mjCMesh: public mjCMesh_, private mjmMesh {
 private:
  void LoadOBJ(mjResource* resource);         // load mesh in wavefront OBJ format
  bool LoadCachedOBJ(const mjCAsset& asset);  // load OBJ from cache asset, return true on success
  void LoadSTL(mjResource* resource);         // load mesh in STL BIN format
  void LoadMSH(mjResource* resource);         // load mesh in MSH BIN format
  void LoadSDF();                             // generate mesh using marching cubes
@@ -870,12 +901,12 @@ class mjCSkin_ : public mjCBase {
  std::vector<int> bodyid;            // body ids
 };
-class mjCSkin: public mjCSkin_, private mjmSkin {
+class mjCSkin: public mjCSkin_, private mjsSkin {
  friend class mjCModel;
  friend class mjXWriter;
 public:
-  mjmSkin spec;
+  mjsSkin spec;
  using mjCBase::name;
  using mjCBase::classname;
  using mjCBase::info;
@@ -901,6 +932,8 @@ class mjCSkin: public mjCSkin_, private mjmSkin {
  mjCSkin& operator=(const mjCSkin& other);  // copy assignment
  ~mjCSkin();                                 // destructor
  void ResolveReferences(const mjCModel* m);
  void NameSpace(const mjCModel* m);
  void Compile(const mjVFS* vfs);             // compiler
  void LoadSKN(mjResource* resource);         // load skin in SKN BIN format
 };
@@ -912,6 +945,8 @@ class mjCSkin: public mjCSkin_, private mjmSkin {
 class mjCHField_ : public mjCBase {
 protected:
  std::vector<float> data;  // elevation data, row-major format
  std::string file_;
  std::string content_type_;
  std::vector<float> userdata_;
@@ -920,13 +955,13 @@ class mjCHField_ : public mjCBase {
  std::vector<float> spec_userdata_;
 };
-class mjCHField : public mjCHField_, private mjmHField {
+class mjCHField : public mjCHField_, private mjsHField {
  friend class mjCGeom;
  friend class mjCModel;
  friend class mjXWriter;
 public:
-  mjmHField spec;
+  mjsHField spec;
  using mjCBase::name;
  using mjCBase::info;
@@ -944,7 +979,6 @@ class mjCHField : public mjCHField_, private mjmHField {
  mjCHField& operator=(const mjCHField& other);  // copy assignment
  ~mjCHField();                                  // destructor
  float* data;                            // elevation data, row-major format
  void Compile(const mjVFS* vfs);         // compiler
  void LoadCustom(mjResource* resource);  // load from custom format
@@ -958,6 +992,8 @@ class mjCHField : public mjCHField_, private mjmHField {
 class mjCTexture_ : public mjCBase {
 protected:
  std::vector<mjtByte> rgb;                   // rgb data
  std::string file_;
  std::string content_type_;
  std::vector<std::string> cubefiles_;
@@ -966,7 +1002,7 @@ class mjCTexture_ : public mjCBase {
  std::vector<std::string> spec_cubefiles_;
 };
-class mjCTexture : public mjCTexture_, private mjmTexture {
+class mjCTexture : public mjCTexture_, private mjsTexture {
  friend class mjCModel;
  friend class mjXReader;
  friend class mjXWriter;
@@ -974,7 +1010,7 @@ class mjCTexture : public mjCTexture_, private mjmTexture {
 public:
  ~mjCTexture();                  // destructor
-  mjmTexture spec;
+  mjsTexture spec;
  using mjCBase::name;
  using mjCBase::classname;
  using mjCBase::info;
@@ -1009,8 +1045,6 @@ class mjCTexture : public mjCTexture_, private mjmTexture {
  void LoadCustom(mjResource* resource,
                  std::vector<unsigned char>& image,
                  unsigned int& w, unsigned int& h);
  mjtByte* rgb;                   // rgb data
 };
@@ -1025,13 +1059,13 @@ class mjCMaterial_ : public mjCBase {
  std::string spec_texture_;
 };
-class mjCMaterial : public mjCMaterial_, private mjmMaterial {
+class mjCMaterial : public mjCMaterial_, private mjsMaterial {
  friend class mjCDef;
  friend class mjCModel;
  friend class mjXWriter;
 public:
-  mjmMaterial spec;
+  mjsMaterial spec;
  using mjCBase::name;
  using mjCBase::classname;
  using mjCBase::info;
@@ -1064,20 +1098,22 @@ class mjCPair_ : public mjCBase {
  std::string spec_geomname2_;
 };
-class mjCPair : public mjCPair_, private mjmPair {
+class mjCPair : public mjCPair_, private mjsPair {
  friend class mjCDef;
  friend class mjCBody;
  friend class mjCModel;
  friend class mjXWriter;
 public:
-  mjmPair spec;
+  mjsPair spec;
  using mjCBase::name;
  using mjCBase::classname;
  using mjCBase::info;
  void CopyFromSpec();
  void PointToLocal();
  void ResolveReferences(const mjCModel* m);
  void NameSpace(const mjCModel* m);
  std::string get_geomname1() { return geomname1_; }
  std::string get_geomname2() { return geomname2_; }
@@ -1114,17 +1150,19 @@ class mjCBodyPair_ : public mjCBase {
  std::string spec_bodyname2_;
 };
-class mjCBodyPair : public mjCBodyPair_, private mjmExclude {
+class mjCBodyPair : public mjCBodyPair_, private mjsExclude {
  friend class mjCBody;
  friend class mjCModel;
 public:
-  mjmExclude spec;
+  mjsExclude spec;
  using mjCBase::name;
  using mjCBase::info;
  void CopyFromSpec();
  void PointToLocal();
  void ResolveReferences(const mjCModel* m);
  void NameSpace(const mjCModel* m);
  std::string get_bodyname1() const { return bodyname1_; }
  std::string get_bodyname2() const { return bodyname2_; }
@@ -1156,20 +1194,22 @@ class mjCEquality_ : public mjCBase {
  std::string spec_name2_;
 };
-class mjCEquality : public mjCEquality_, private mjmEquality {
+class mjCEquality : public mjCEquality_, private mjsEquality {
  friend class mjCDef;
  friend class mjCBody;
  friend class mjCModel;
  friend class mjXWriter;
 public:
-  mjmEquality spec;
+  mjsEquality spec;
  using mjCBase::name;
  using mjCBase::classname;
  using mjCBase::info;
  void CopyFromSpec();
  void PointToLocal();
  void ResolveReferences(const mjCModel* m);
  void NameSpace(const mjCModel* m);
 private:
  mjCEquality(mjCModel* = 0, mjCDef* = 0);           // constructor
@@ -1195,13 +1235,13 @@ class mjCTendon_ : public mjCBase {
  std::vector<double> spec_userdata_;
 };
-class mjCTendon : public mjCTendon_, private mjmTendon {
+class mjCTendon : public mjCTendon_, private mjsTendon {
  friend class mjCDef;
  friend class mjCModel;
  friend class mjXWriter;
 public:
-  mjmTendon spec;
+  mjsTendon spec;
  using mjCBase::name;
  using mjCBase::classname;
  using mjCBase::info;
@@ -1227,6 +1267,9 @@ class mjCTendon : public mjCTendon_, private mjmTendon {
  void CopyFromSpec();
  void PointToLocal();
  void ResolveReferences(const mjCModel* m);
  void NameSpace(const mjCModel* m);
  void SetModel(mjCModel* _model);
  bool is_limited() const;
@@ -1252,15 +1295,18 @@ class mjCWrap_ : public mjCBase {
  std::string sidesite;           // name of side site
 };
-class mjCWrap : public mjCWrap_, private mjmWrap {
+class mjCWrap : public mjCWrap_, private mjsWrap {
  friend class mjCTendon;
  friend class mjCModel;
 public:
-  mjmWrap spec;
+  mjsWrap spec;
  using mjCBase::info;
  void PointToLocal();
  void ResolveReferences(const mjCModel* m);
  void NameSpace(const mjCModel* m);
  mjCBase* obj;                   // wrap object pointer
 private:
@@ -1268,8 +1314,6 @@ class mjCWrap : public mjCWrap_, private mjmWrap {
  mjCWrap(const mjCWrap& other);             // copy constructor
  mjCWrap& operator=(const mjCWrap& other);  // copy assignment
  void Compile(void);                 // compiler
  mjCTendon* tendon;              // tendon owning this wrap
 };
@@ -1293,12 +1337,12 @@ class mjCPlugin : public mjCPlugin_ {
  friend class mjXWriter;
 public:
-  mjmPlugin spec;
+  mjsPlugin spec;
  mjCBase* parent;   // parent object (only used when generating error message)
  mjCPlugin(const mjCPlugin& other);             // copy constructor
 private:
  mjCPlugin(mjCModel*);                          // constructor
  mjCPlugin(const mjCPlugin& other);             // copy constructor
  mjCPlugin& operator=(const mjCPlugin& other);  // copy assignment
  void Compile(void);              // compiler
@@ -1326,13 +1370,13 @@ class mjCActuator_ : public mjCBase {
  std::vector<double> spec_userdata_;
 };
-class mjCActuator : public mjCActuator_, private mjmActuator {
+class mjCActuator : public mjCActuator_, private mjsActuator {
  friend class mjCDef;
  friend class mjCModel;
  friend class mjXWriter;
 public:
-  mjmActuator spec;
+  mjsActuator spec;
  using mjCBase::name;
  using mjCBase::classname;
  using mjCBase::info;
@@ -1355,6 +1399,10 @@ class mjCActuator : public mjCActuator_, private mjmActuator {
  void Compile(void);                       // compiler
  void CopyFromSpec();
  void PointToLocal();
  void ResolveReferences(const mjCModel* m);
  void NameSpace(const mjCModel* m);
  mjCBase* ptarget;  // transmission target
 };
@@ -1377,13 +1425,13 @@ class mjCSensor_ : public mjCBase {
  std::vector<double> spec_userdata_;
 };
-class mjCSensor : public mjCSensor_, private mjmSensor {
+class mjCSensor : public mjCSensor_, private mjsSensor {
  friend class mjCDef;
  friend class mjCModel;
  friend class mjXWriter;
 public:
-  mjmSensor spec;
+  mjsSensor spec;
  using mjCBase::name;
  using mjCBase::classname;
  using mjCBase::info;
@@ -1400,9 +1448,12 @@ class mjCSensor : public mjCSensor_, private mjmSensor {
  void Compile(void);             // compiler
  void CopyFromSpec();
-  void MakePointerLocal();
+  void PointToLocal();
  void ResolveReferences(const mjCModel* m);
  void NameSpace(const mjCModel* m);
  mjCBase* obj;                   // sensorized object
  mjCBase* ref;                   // sensorized reference
 };
@@ -1416,12 +1467,12 @@ class mjCNumeric_ : public mjCBase {
  std::vector<double> spec_data_;
 };
-class mjCNumeric : public mjCNumeric_, private mjmNumeric {
+class mjCNumeric : public mjCNumeric_, private mjsNumeric {
  friend class mjCModel;
  friend class mjXWriter;
 public:
-  mjmNumeric spec;
+  mjsNumeric spec;
  using mjCBase::name;
  using mjCBase::info;
@@ -1448,12 +1499,12 @@ class mjCText_ : public mjCBase {
  std::string spec_data_;
 };
-class mjCText : public mjCText_, private mjmText {
+class mjCText : public mjCText_, private mjsText {
  friend class mjCModel;
  friend class mjXWriter;
 public:
-  mjmText spec;
+  mjsText spec;
  using mjCBase::name;
  using mjCBase::info;
@@ -1485,17 +1536,19 @@ class mjCTuple_ : public mjCBase {
  std::vector<double> spec_objprm_;
 };
-class mjCTuple : public mjCTuple_, private mjmTuple {
+class mjCTuple : public mjCTuple_, private mjsTuple {
  friend class mjCModel;
  friend class mjXWriter;
 public:
-  mjmTuple spec;
+  mjsTuple spec;
  using mjCBase::name;
  using mjCBase::info;
  void PointToLocal();
  void CopyFromSpec();
  void ResolveReferences(const mjCModel* m);
  void NameSpace(const mjCModel* m);
 private:
  mjCTuple(mjCModel*);                         // constructor
@@ -1527,12 +1580,12 @@ class mjCKey_ : public mjCBase {
  std::vector<double> spec_ctrl_;
 };
-class mjCKey : public mjCKey_, private mjmKey {
+class mjCKey : public mjCKey_, private mjsKey {
  friend class mjCModel;
  friend class mjXWriter;
 public:
-  mjmKey spec;
+  mjsKey spec;
  using mjCBase::name;
  using mjCBase::info;
@@ -1553,7 +1606,7 @@ class mjCKey : public mjCKey_, private mjmKey {
 //------------------------- class mjCDef -----------------------------------------------------------
 // Describes one set of defaults
-class mjCDef {
+class mjCDef : public mjElement {
  friend class mjXWriter;
 public:
@@ -1569,7 +1622,7 @@ class mjCDef {
  int parentid;                   // id of parent class
  std::vector<int> childid;       // ids of child classes
-  mjmDefault spec;
+  mjsDefault spec;
  // default objects (TODO: they should become private)
  mjCJoint    joint;
@@ -15,7 +15,7 @@
 #include "xml/xml.h"
 #include <locale.h>
-#include "user/user_api.h"
+#include <cstring>
 #if defined(__APPLE__) || defined(__FreeBSD__)
 #include <xlocale.h>
@@ -29,6 +29,7 @@
 #include "tinyxml2.h"
 #include <mujoco/mujoco.h>
 #include <mujoco/mjmodel.h>
 #include <mujoco/mjplugin.h>
 #include "cc/array_safety.h"
@@ -344,14 +345,14 @@ mjSpec* mjParseXML(const char* filename, const mjVFS* vfs,
  }
  // create model, set filedir
-  model = mjm_createSpec();
+  model = mjs_createSpec();
  const char* dir;
  int ndir = 0;
  mju_getResourceDir(resource, &dir, &ndir);
  if (dir != nullptr) {
-    mjm_setString(model->modelfiledir, std::string(dir, ndir).c_str());
+    mjs_setString(model->modelfiledir, std::string(dir, ndir).c_str());
  } else {
-    mjm_setString(model->modelfiledir, "");
+    mjs_setString(model->modelfiledir, "");
  }
  // close resource
@@ -363,8 +364,8 @@ mjSpec* mjParseXML(const char* filename, const mjVFS* vfs,
      // find include elements, replace them with subtree from xml file
      std::unordered_set<std::string> included = {filename};
      mjXReader parser;
-      parser.SetModelFileDir(mjm_getString(model->modelfiledir));
+      parser.SetModelFileDir(mjs_getString(model->modelfiledir));
-      mjIncludeXML(parser, root, mjm_getString(model->modelfiledir), vfs, included);
+      mjIncludeXML(parser, root, mjs_getString(model->modelfiledir), vfs, included);
      // parse MuJoCo model
      parser.SetModel(model);
@@ -393,9 +394,39 @@ mjSpec* mjParseXML(const char* filename, const mjVFS* vfs,
  // catch known errors
  catch (mjXError err) {
    mjCopyError(error, err.message, error_sz);
-    mjm_deleteSpec(model);
+    mjs_deleteSpec(model);
    return nullptr;
  }
  return model;
 }
 static void RegisterResourceProvider() {
  // register string resource provider if not registered before
  if (mjp_getResourceProvider("LoadModelFromString:") == nullptr) {
    mjpResourceProvider resourceProvider;
    mjp_defaultResourceProvider(&resourceProvider);
    resourceProvider.prefix = "LoadModelFromString";
    resourceProvider.open = +[](mjResource* resource) {
      resource->data = &(resource->name[strlen("LoadModelFromString:")]);
      return 1;
    };
    resourceProvider.read =
        +[](mjResource* resource, const void** buffer) {
          *buffer = resource->data;
          return (int) strlen((const char*) resource->data);
        };
    resourceProvider.close = +[](mjResource* resource) {};
    mjp_registerResourceProvider(&resourceProvider);
  }
 }
 mjSpec* ParseSpecFromString(std::string_view xml, char* error,
                            int error_size, mjVFS* vfs) {
  RegisterResourceProvider();
  std::string xml2 = {xml.begin(), xml.end()};
  std::string str = "LoadModelFromString:" +  xml2;
  return mjParseXML(str.c_str(), vfs, error, error_size);
 }
@@ -29,5 +29,10 @@ std::string mjWriteXML(mjSpec* model, char* error, int error_sz);
 // Main parser function
 MJAPI mjSpec* mjParseXML(const char* filename, const mjVFS* vfs, char* error, int error_sz);
 // Returns a newly-allocated mjSpec, loaded from the contents of xml.
 // On failure returns nullptr and populates the error array if present.
 MJAPI mjSpec* ParseSpecFromString(std::string_view xml, char* error = nullptr,
                                  int error_size = 0, mjVFS* vfs = nullptr);
 #endif  // MUJOCO_SRC_XML_XML_H_
@@ -56,7 +56,7 @@ std::optional<std::string> GlobalModel::ToXML(const mjModel* m, char* error,
    mjCopyError(error, "No XML model loaded", error_sz);
    return std::nullopt;
  }
-  mjm_copyBack(model_, m);
+  mjs_copyBack(model_, m);
  std::string result = mjWriteXML(model_, error, error_sz);
  if (result.empty()) {
    return std::nullopt;
@@ -67,7 +67,7 @@ std::optional<std::string> GlobalModel::ToXML(const mjModel* m, char* error,
 void GlobalModel::Set(mjSpec* model) {
  std::lock_guard<std::mutex> lock(*mutex_);
  if (model_ != nullptr) {
-    mjm_deleteSpec(model_);
+    mjs_deleteSpec(model_);
  }
  model_ = model;
 }
@@ -93,21 +93,21 @@ mjModel* mj_loadXML(const char* filename, const mjVFS* vfs,
  // parse new model
  std::unique_ptr<mjSpec, std::function<void(mjSpec*)>> model(
      mjParseXML(filename, vfs, error, error_sz),
-      [](mjSpec* m) { mjm_deleteSpec(m); });
+      [](mjSpec* m) { mjs_deleteSpec(m); });
  if (!model) {
    return nullptr;
  }
  // compile new model
-  mjModel* m = mjm_compile(model.get(), vfs);
+  mjModel* m = mjs_compile(model.get(), vfs);
  if (!m) {
-    mjCopyError(error, mjm_getError(model.get()), error_sz);
+    mjCopyError(error, mjs_getError(model.get()), error_sz);
    return nullptr;
  }
  // handle compile warning
-  if (mjm_isWarning(model.get())) {
+  if (mjs_isWarning(model.get())) {
-    mjCopyError(error, mjm_getError(model.get()), error_sz);
+    mjCopyError(error, mjs_getError(model.get()), error_sz);
  } else if (error) {
    error[0] = '\0';
  }
@@ -24,6 +24,7 @@
 #include "user/user_api.h"
 #include "user/user_model.h"
 #include "user/user_objects.h"
 #include "xml/xml_util.h"
 #include "tinyxml2.h"
 namespace {
@@ -51,7 +52,7 @@ void mjXBase::SetModel(mjSpec* _model) {
 // read alternative orientation specification
-int mjXBase::ReadAlternative(XMLElement* elem, mjmOrientation& alt) {
+int mjXBase::ReadAlternative(XMLElement* elem, mjsOrientation& alt) {
  string text;
  int read = (int)(elem->Attribute("quat") != 0) +
             (ReadAttr(elem, "axisangle", 4, alt.axisangle, text) ? 1 : 0) +
@@ -90,7 +90,7 @@ class mjXBase : public mjXUtil {
  virtual void SetModel(mjSpec*);
  // read alternative orientation specification
-  static int ReadAlternative(tinyxml2::XMLElement* elem, mjmOrientation& alt);
+  static int ReadAlternative(tinyxml2::XMLElement* elem, mjsOrientation& alt);
 protected:
  mjSpec* model;                    // internally-allocated model
@@ -54,8 +54,8 @@ class mjXReader : public mjXBase {
  void Visual(tinyxml2::XMLElement* section);                          // visual section
  void Statistic(tinyxml2::XMLElement* section);                       // statistic section
  void Asset(tinyxml2::XMLElement* section);                           // asset section
-  void Body(tinyxml2::XMLElement* section, mjmBody* pbody,
+  void Body(tinyxml2::XMLElement* section, mjsBody* pbody,
-            mjmFrame* pframe);                                         // body/world section
+            mjsFrame* pframe);                                         // body/world section
  void Contact(tinyxml2::XMLElement* section);                         // contact section
  void Deformable(tinyxml2::XMLElement* section);                      // deformable section
  void Equality(tinyxml2::XMLElement* section);                        // equality section
@@ -65,25 +65,25 @@ class mjXReader : public mjXBase {
  void Keyframe(tinyxml2::XMLElement* section);                        // keyframe section
  // single element parsers, used in defaults and main body
-  void OneFlex(tinyxml2::XMLElement* elem, mjmFlex* pflex);
+  void OneFlex(tinyxml2::XMLElement* elem, mjsFlex* pflex);
-  void OneMesh(tinyxml2::XMLElement* elem, mjmMesh* pmesh);
+  void OneMesh(tinyxml2::XMLElement* elem, mjsMesh* pmesh);
-  void OneSkin(tinyxml2::XMLElement* elem, mjmSkin* pskin);
+  void OneSkin(tinyxml2::XMLElement* elem, mjsSkin* pskin);
-  void OneMaterial(tinyxml2::XMLElement* elem, mjmMaterial* pmaterial);
+  void OneMaterial(tinyxml2::XMLElement* elem, mjsMaterial* pmaterial);
-  void OneJoint(tinyxml2::XMLElement* elem, mjmJoint* pjoint);
+  void OneJoint(tinyxml2::XMLElement* elem, mjsJoint* pjoint);
-  void OneGeom(tinyxml2::XMLElement* elem, mjmGeom* pgeom);
+  void OneGeom(tinyxml2::XMLElement* elem, mjsGeom* pgeom);
-  void OneSite(tinyxml2::XMLElement* elem, mjmSite* site);
+  void OneSite(tinyxml2::XMLElement* elem, mjsSite* site);
-  void OneCamera(tinyxml2::XMLElement* elem, mjmCamera* pcamera);
+  void OneCamera(tinyxml2::XMLElement* elem, mjsCamera* pcamera);
-  void OneLight(tinyxml2::XMLElement* elem, mjmLight* plight);
+  void OneLight(tinyxml2::XMLElement* elem, mjsLight* plight);
-  void OnePair(tinyxml2::XMLElement* elem, mjmPair* ppair);
+  void OnePair(tinyxml2::XMLElement* elem, mjsPair* ppair);
-  void OneEquality(tinyxml2::XMLElement* elem, mjmEquality* pequality);
+  void OneEquality(tinyxml2::XMLElement* elem, mjsEquality* pequality);
-  void OneTendon(tinyxml2::XMLElement* elem, mjmTendon* ptendon);
+  void OneTendon(tinyxml2::XMLElement* elem, mjsTendon* ptendon);
-  void OneActuator(tinyxml2::XMLElement* elem, mjmActuator* pactuator);
+  void OneActuator(tinyxml2::XMLElement* elem, mjsActuator* pactuator);
-  void OneComposite(tinyxml2::XMLElement* elem, mjmBody* pbody, mjmDefault* def);
+  void OneComposite(tinyxml2::XMLElement* elem, mjsBody* pbody, mjsDefault* def);
-  void OneFlexcomp(tinyxml2::XMLElement* elem, mjmBody* pbody);
+  void OneFlexcomp(tinyxml2::XMLElement* elem, mjsBody* pbody);
-  void OnePlugin(tinyxml2::XMLElement* elem, mjmPlugin* plugin);
+  void OnePlugin(tinyxml2::XMLElement* elem, mjsPlugin* plugin);
  mjXSchema schema;                                                   // schema used for validation
-  mjmDefault* GetClass(tinyxml2::XMLElement* section);                    // get default class name
+  mjsDefault* GetClass(tinyxml2::XMLElement* section);                    // get default class name
  bool readingdefaults;  // true while reading defaults
@@ -307,6 +307,7 @@ void mjXWriter::OneJoint(XMLElement* elem, mjCJoint* pjoint, mjCDef* def) {
  WriteAttr(elem, "range", 2, pjoint->range, def->joint.range);
  WriteAttrKey(elem, "actuatorfrclimited", TFAuto_map, 3, pjoint->actfrclimited,
               def->joint.actfrclimited);
  WriteAttrKey(elem, "actuatorgravcomp", bool_map, 2, pjoint->actgravcomp, def->joint.actgravcomp);
  WriteAttr(elem, "actuatorfrcrange", 2, pjoint->actfrcrange, def->joint.actfrcrange);
  WriteAttr(elem, "margin", 1, &pjoint->margin, &def->joint.margin);
  WriteAttr(elem, "armature", 1, &pjoint->armature, &def->joint.armature);
@@ -553,33 +554,33 @@ void mjXWriter::OneEquality(XMLElement* elem, mjCEquality* peq, mjCDef* def) {
    switch (peq->type) {
    case mjEQ_CONNECT:
-      WriteAttrTxt(elem, "body1", mjm_getString(peq->name1));
+      WriteAttrTxt(elem, "body1", mjs_getString(peq->name1));
-      WriteAttrTxt(elem, "body2", mjm_getString(peq->name2));
+      WriteAttrTxt(elem, "body2", mjs_getString(peq->name2));
      WriteAttr(elem, "anchor", 3, peq->data);
      break;
    case mjEQ_WELD:
-      WriteAttrTxt(elem, "body1", mjm_getString(peq->name1));
+      WriteAttrTxt(elem, "body1", mjs_getString(peq->name1));
-      WriteAttrTxt(elem, "body2", mjm_getString(peq->name2));
+      WriteAttrTxt(elem, "body2", mjs_getString(peq->name2));
      WriteAttr(elem, "anchor", 3, peq->data);
      WriteAttr(elem, "torquescale", 1, peq->data+10);
      WriteAttr(elem, "relpose", 7, peq->data+3);
      break;
    case mjEQ_JOINT:
-      WriteAttrTxt(elem, "joint1", mjm_getString(peq->name1));
+      WriteAttrTxt(elem, "joint1", mjs_getString(peq->name1));
-      WriteAttrTxt(elem, "joint2", mjm_getString(peq->name2));
+      WriteAttrTxt(elem, "joint2", mjs_getString(peq->name2));
      WriteAttr(elem, "polycoef", 5, peq->data);
      break;
    case mjEQ_TENDON:
-      WriteAttrTxt(elem, "tendon1", mjm_getString(peq->name1));
+      WriteAttrTxt(elem, "tendon1", mjs_getString(peq->name1));
-      WriteAttrTxt(elem, "tendon2", mjm_getString(peq->name2));
+      WriteAttrTxt(elem, "tendon2", mjs_getString(peq->name2));
      WriteAttr(elem, "polycoef", 5, peq->data);
      break;
    case mjEQ_FLEX:
-      WriteAttrTxt(elem, "flex", mjm_getString(peq->name1));
+      WriteAttrTxt(elem, "flex", mjs_getString(peq->name1));
      break;
    default:
@@ -731,16 +732,16 @@ void mjXWriter::OneActuator(XMLElement* elem, mjCActuator* pact, mjCDef* def) {
 // write plugin
-void mjXWriter::OnePlugin(XMLElement* elem, mjmPlugin* plugin) {
+void mjXWriter::OnePlugin(XMLElement* elem, mjsPlugin* plugin) {
-  const std::string instance_name = std::string(mjm_getString(plugin->instance_name));
+  const std::string instance_name = std::string(mjs_getString(plugin->instance_name));
-  const std::string plugin_name = std::string(mjm_getString(plugin->name));
+  const std::string plugin_name = std::string(mjs_getString(plugin->name));
  if (!instance_name.empty()) {
    WriteAttrTxt(elem, "instance", instance_name);
  } else {
    WriteAttrTxt(elem, "plugin", plugin_name);
    const mjpPlugin* pplugin = mjp_getPluginAtSlot(
-        ((mjCPlugin*)plugin->instance)->spec.plugin_slot);
+        static_cast<mjCPlugin*>(plugin->instance)->spec.plugin_slot);
-    const char* c = &((mjCPlugin*)plugin->instance)->flattened_attributes[0];
+    const char* c = &(static_cast<mjCPlugin*>(plugin->instance)->flattened_attributes[0]);
    for (int i = 0; i < pplugin->nattribute; ++i) {
      std::string value(c);
      if (!value.empty()) {
@@ -783,13 +784,13 @@ string mjXWriter::Write(char *error, size_t error_sz) {
  // create document and root
  XMLDocument doc;
  XMLElement* root = doc.NewElement("mujoco");
-  root->SetAttribute("model", mjm_getString(model->modelname));
+  root->SetAttribute("model", mjs_getString(model->modelname));
  // insert root
  doc.InsertFirstChild(root);
  // write comment if present
-  string text = mjm_getString(model->comment);
+  string text = mjs_getString(model->comment);
  if (!text.empty()) {
    XMLComment* comment = doc.NewComment(text.c_str());
    root->LinkEndChild(comment);
@@ -937,7 +938,6 @@ void mjXWriter::Option(XMLElement* root) {
    WRITEENBL("energy",         mjENBL_ENERGY)
    WRITEENBL("fwdinv",         mjENBL_FWDINV)
    WRITEENBL("invdiscrete",    mjENBL_INVDISCRETE)
    WRITEENBL("sensornoise",    mjENBL_SENSORNOISE)
    WRITEENBL("multiccd",       mjENBL_MULTICCD)
    WRITEENBL("island",         mjENBL_ISLAND)
 #undef WRITEENBL
@@ -72,7 +72,7 @@ class mjXWriter : public mjXBase {
  void OneEquality(tinyxml2::XMLElement* elem,  mjCEquality* pequality, mjCDef* def);
  void OneTendon(tinyxml2::XMLElement* elem,    mjCTendon* ptendon,     mjCDef* def);
  void OneActuator(tinyxml2::XMLElement* elem,  mjCActuator* pactuator, mjCDef* def);
-  void OnePlugin(tinyxml2::XMLElement* elem,    mjmPlugin* plugin);
+  void OnePlugin(tinyxml2::XMLElement* elem,    mjsPlugin* plugin);
  bool writingdefaults;                       // true during defaults write
 };
@@ -20,7 +20,6 @@
 #include <mujoco/mjmodel.h>
 #include "user/user_api.h"
 #include "user/user_objects.h"
 #include "user/user_util.h"
 #include "xml/xml_native_reader.h"
 #include "xml/xml_urdf.h"
@@ -112,7 +111,7 @@ void mjXURDF::Parse(
  // get model name
  std::string modelname;
  if (ReadAttrTxt(root, "name", modelname)) {
-    mjm_setString(model->modelname, modelname.c_str());
+    mjs_setString(model->modelname, modelname.c_str());
  }
  // find and register all materials
@@ -206,16 +205,16 @@ void mjXURDF::Parse(
  // override the pose for the base link and add a free joint
  for (int i = 0; i < (int)urName.size(); i++) {
    if (urParent[i] < 0) {
-      mjmBody* world = mjm_findBody(model, "world");
+      mjsBody* world = mjs_findBody(model, "world");
-      mjmBody* pbody = mjm_findChild(world, urName[i].c_str());
+      mjsBody* pbody = mjs_findChild(world, urName[i].c_str());
      mjuu_copyvec(pbody->pos, pos, 3);
      mjuu_copyvec(pbody->quat, quat, 4);
      // add a free joint to allow motion of the body
      // if the mass is 0, assume the object is static
      if (!static_body && pbody->mass > 0) {
-        mjmJoint* pjoint = mjm_addJoint(pbody, 0);
+        mjsJoint* pjoint = mjs_addJoint(pbody, 0);
-        mjm_setString(pjoint->name, (urName[i] + "_free_joint").c_str());
+        mjs_setString(pjoint->name, (urName[i] + "_free_joint").c_str());
        pjoint->type = mjJNT_FREE;
      }
    }
@@ -226,14 +225,14 @@ void mjXURDF::Parse(
 void mjXURDF::Body(XMLElement* body_elem) {
  std::string name, text;
  XMLElement *elem, *temp, *temp1;
-  mjmBody *pbody, *world;
+  mjsBody *pbody, *world;
-  mjmGeom* pgeom;
+  mjsGeom* pgeom;
-  // get body name and pointer to mjmBody
+  // get body name and pointer to mjsBody
  ReadAttrTxt(body_elem, "name", name, true);
  name = GetPrefixedName(name);
-  world = mjm_findBody(model, "world");
+  world = mjs_findBody(model, "world");
-  pbody = mjm_findChild(world, name.c_str());
+  pbody = mjs_findChild(world, name.c_str());
  if (!pbody) {
    throw mjXError(body_elem, "URDF body not found");  // SHOULD NOT OCCUR
  }
@@ -272,7 +271,7 @@ void mjXURDF::Body(XMLElement* body_elem) {
    //  lquat = rotation from specified to default (joint/body) inertial frame
    double lquat[4] = {1, 0, 0, 0};
    double tmpquat[4] = {1, 0, 0, 0};
-    const char* altres = mjm_setFullInertia(pbody, lquat, pbody->inertia);
+    const char* altres = mjs_setFullInertia(pbody, lquat, pbody->inertia);
    // inertia are sometimes 0 in URDF files: ignore error in altres, fix later
    (void) altres;
@@ -326,7 +325,7 @@ void mjXURDF::Body(XMLElement* body_elem) {
        mjXUtil::ReadAttrTxt(elem, "name", geom_name);
        name = GetPrefixedName(name);
        if (urGeomNames.find(geom_name) == urGeomNames.end()) {
-          mjm_setString(pgeom->name, geom_name.c_str());
+          mjs_setString(pgeom->name, geom_name.c_str());
          urGeomNames.insert(geom_name);
        } else {
          std::cerr << "WARNING: Geom with duplicate name '" << geom_name
@@ -349,7 +348,7 @@ void mjXURDF::Body(XMLElement* body_elem) {
      mjXUtil::ReadAttrTxt(elem, "name", geom_name);
      geom_name = GetPrefixedName(geom_name);
      if (urGeomNames.find(geom_name) == urGeomNames.end()) {
-        mjm_setString(pgeom->name, geom_name.c_str());
+        mjs_setString(pgeom->name, geom_name.c_str());
        urGeomNames.insert(geom_name);
      } else {
        std::cerr << "WARNING: Geom with duplicate name '" << geom_name
@@ -374,8 +373,8 @@ void mjXURDF::Parse(XMLElement* root) {
 void mjXURDF::Joint(XMLElement* joint_elem) {
  std::string jntname, name, text;
  XMLElement *elem;
-  mjmBody *pbody, *parent, *world;
+  mjsBody *pbody, *parent, *world;
-  mjmJoint *pjoint=0, *pjoint1=0, *pjoint2=0;
+  mjsJoint *pjoint=0, *pjoint1=0, *pjoint2=0;
  int jointtype;
  // get type and name
@@ -390,8 +389,8 @@ void mjXURDF::Joint(XMLElement* joint_elem) {
  elem = FindSubElem(joint_elem, "parent", true);
  ReadAttrTxt(elem, "link", name, true);
  name = GetPrefixedName(name);
-  world = mjm_findBody(model, "world");
+  world = mjs_findBody(model, "world");
-  parent = mjm_findChild(world, name.c_str());
+  parent = mjs_findChild(world, name.c_str());
  if (!parent) {                      // SHOULD NOT OCCUR
    throw mjXError(elem, "invalid parent name in URDF joint definition");
  }
@@ -400,8 +399,8 @@ void mjXURDF::Joint(XMLElement* joint_elem) {
  elem = FindSubElem(joint_elem, "child", true);
  ReadAttrTxt(elem, "link", name, true);
  name = GetPrefixedName(name);
-  world = mjm_findBody(model, "world");
+  world = mjs_findBody(model, "world");
-  pbody = mjm_findChild(world, name.c_str());
+  pbody = mjs_findChild(world, name.c_str());
  if (!pbody) {                       // SHOULD NOT OCCUR
    throw mjXError(elem, "invalid child name in URDF joint definition");
  }
@@ -418,16 +417,16 @@ void mjXURDF::Joint(XMLElement* joint_elem) {
  switch (jointtype) {
  case 0:     // revolute
  case 1:     // continuous
-    pjoint = mjm_addJoint(pbody, 0);
+    pjoint = mjs_addJoint(pbody, 0);
-    mjm_setString(pjoint->name, jntname.c_str());
+    mjs_setString(pjoint->name, jntname.c_str());
    pjoint->type = mjJNT_HINGE;
    mjuu_setvec(pjoint->pos, 0, 0, 0);
    mjuu_copyvec(pjoint->axis, axis, 3);
    break;
  case 2:     // prismatic
-    pjoint = mjm_addJoint(pbody, 0);
+    pjoint = mjs_addJoint(pbody, 0);
-    mjm_setString(pjoint->name, jntname.c_str());
+    mjs_setString(pjoint->name, jntname.c_str());
    pjoint->type = mjJNT_SLIDE;
    mjuu_setvec(pjoint->pos, 0, 0, 0);
    mjuu_copyvec(pjoint->axis, axis, 3);
@@ -437,8 +436,8 @@ void mjXURDF::Joint(XMLElement* joint_elem) {
    return;
  case 4:     // floating
-    pjoint = mjm_addJoint(pbody, 0);
+    pjoint = mjs_addJoint(pbody, 0);
-    mjm_setString(pjoint->name, jntname.c_str());
+    mjs_setString(pjoint->name, jntname.c_str());
    pjoint->type = mjJNT_FREE;
    break;
@@ -448,8 +447,8 @@ void mjXURDF::Joint(XMLElement* joint_elem) {
    mjuu_quat2mat(mat, quat);
    // construct slider along x
-    pjoint = mjm_addJoint(pbody, 0);
+    pjoint = mjs_addJoint(pbody, 0);
-    mjm_setString(pjoint->name, (jntname + "_TX").c_str());
+    mjs_setString(pjoint->name, (jntname + "_TX").c_str());
    pjoint->type = mjJNT_SLIDE;
    tmpaxis[0] = mat[0];
    tmpaxis[1] = mat[3];
@@ -458,8 +457,8 @@ void mjXURDF::Joint(XMLElement* joint_elem) {
    mjuu_copyvec(pjoint->axis, tmpaxis, 3);
    // construct slider along y
-    pjoint1 = mjm_addJoint(pbody, 0);
+    pjoint1 = mjs_addJoint(pbody, 0);
-    mjm_setString(pjoint1->name, (jntname + "_TY").c_str());
+    mjs_setString(pjoint1->name, (jntname + "_TY").c_str());
    pjoint1->type = mjJNT_SLIDE;
    tmpaxis[0] = mat[1];
    tmpaxis[1] = mat[4];
@@ -468,8 +467,8 @@ void mjXURDF::Joint(XMLElement* joint_elem) {
    mjuu_copyvec(pjoint1->axis, tmpaxis, 3);
    // construct hinge around z = locaxis
-    pjoint2 = mjm_addJoint(pbody, 0);
+    pjoint2 = mjs_addJoint(pbody, 0);
-    mjm_setString(pjoint2->name, (jntname + "_RZ").c_str());
+    mjs_setString(pjoint2->name, (jntname + "_RZ").c_str());
    pjoint2->type = mjJNT_HINGE;
    mjuu_setvec(pjoint2->pos, 0, 0, 0);
    mjuu_copyvec(pjoint2->axis, axis, 3);
@@ -506,7 +505,7 @@ void mjXURDF::Joint(XMLElement* joint_elem) {
 // parse origin and geometry elements of visual or collision
-mjmGeom* mjXURDF::Geom(XMLElement* geom_elem, mjmBody* pbody, bool collision) {
+mjsGeom* mjXURDF::Geom(XMLElement* geom_elem, mjsBody* pbody, bool collision) {
  XMLElement *elem, *temp;
  std::string text, meshfile;
@@ -514,8 +513,8 @@ mjmGeom* mjXURDF::Geom(XMLElement* geom_elem, mjmBody* pbody, bool collision) {
  elem = FindSubElem(geom_elem, "geometry", true);
  // add BOX geom, modify type later
-  mjmGeom* pgeom = mjm_addGeom(pbody, 0);
+  mjsGeom* pgeom = mjs_addGeom(pbody, 0);
-  mjm_setString(pgeom->name, "");
+  mjs_setString(pgeom->name, "");
  pgeom->type = mjGEOM_BOX;
  if (collision) {
    pgeom->contype = 1;
@@ -576,19 +575,19 @@ mjmGeom* mjXURDF::Geom(XMLElement* geom_elem, mjmBody* pbody, bool collision) {
    meshname = mjuu_stripext(meshname);
    // look for existing mesh
-    mjmMesh* mesh = mjm_findMesh(model, meshname.c_str());
+    mjsMesh* mesh = mjs_findMesh(model, meshname.c_str());
-    mjmMesh* pmesh = 0;
+    mjsMesh* pmesh = 0;
    // does not exist: create
    if (!mesh) {
-      pmesh = mjm_addMesh(model, 0);
+      pmesh = mjs_addMesh(model, 0);
    }
    // exists with different scale: append name with '1', create
    else if (mesh->scale[0]!=meshscale[0] ||
             mesh->scale[1]!=meshscale[1] ||
             mesh->scale[2]!=meshscale[2]) {
-      pmesh = mjm_addMesh(model, 0);
+      pmesh = mjs_addMesh(model, 0);
      meshname = meshname + "1";
    }
@@ -598,9 +597,9 @@ mjmGeom* mjXURDF::Geom(XMLElement* geom_elem, mjmBody* pbody, bool collision) {
    }
    // set fields
-    mjm_setString(pmesh->file, meshfile.c_str());
+    mjs_setString(pmesh->file, meshfile.c_str());
-    mjm_setString(pmesh->name, meshname.c_str());
+    mjs_setString(pmesh->name, meshname.c_str());
-    mjm_setString(pgeom->meshname, meshname.c_str());
+    mjs_setString(pgeom->meshname, meshname.c_str());
    pmesh->scale[0] = meshscale[0];
    pmesh->scale[1] = meshscale[1];
    pmesh->scale[2] = meshscale[2];
@@ -633,9 +632,10 @@ void mjXURDF::Origin(XMLElement* origin_elem, double* pos, double* quat) {
    ReadAttr(temp, "xyz", 3, pos, text);
    // orientation
-    mjCAlternative alt;
+    mjsOrientation alt;
    mjs_defaultOrientation(alt);
    if (ReadAttr(temp, "rpy", 3, alt.euler, text)) {
-      alt.Set(quat, 0, "XYZ");
+      mjs_resolveOrientation(quat, 0, "XYZ", &alt);
    }
  }
 }
@@ -683,22 +683,22 @@ void mjXURDF::AddBody(std::string name) {
 // add body with given number to the mjCModel tree, process children
 void mjXURDF::AddToTree(int n) {
  // get pointer to parent in mjCModel tree
-  mjmBody *parent = 0, *child = 0, *world = 0;
+  mjsBody *parent = 0, *child = 0, *world = 0;
  if (urParent[n]>=0) {
-    world = mjm_findBody(model, "world");
+    world = mjs_findBody(model, "world");
-    parent = mjm_findChild(world, urName[urParent[n]].c_str());
+    parent = mjs_findChild(world, urName[urParent[n]].c_str());
    if (!parent)
      throw mjXError(0, "URDF body parent should already be in tree: %s",
                     urName[urParent[n]].c_str());       // SHOULD NOT OCCUR
  } else {
-    parent = mjm_findBody(model, "world");
+    parent = mjs_findBody(model, "world");
  }
  // add this body
  if (urName[n] != "world") {
-    child = mjm_addBody(parent, 0);
+    child = mjs_addBody(parent, 0);
-    mjm_setString(child->name, urName[n].c_str());
+    mjs_setString(child->name, urName[n].c_str());
  }
  // add children recursively
@@ -51,8 +51,8 @@ class mjXURDF : public mjXBase {
  void AddToTree(int n);                                           // add body to mjCModel tree
  void Body(tinyxml2::XMLElement* body_elem);                      // parse body
  void Joint(tinyxml2::XMLElement* joint_elem);                    // parse joint
-  mjmGeom* Geom(tinyxml2::XMLElement* geom_elem,
+  mjsGeom* Geom(tinyxml2::XMLElement* geom_elem,
-                mjmBody* pbody, bool collision);      // parse origin and geometry of geom
+                mjsBody* pbody, bool collision);      // parse origin and geometry of geom
  void Origin(tinyxml2::XMLElement* origin_elem, double* pos, double* quat); // parse origin element
  void MakeMaterials(tinyxml2::XMLElement* elem);     // find all materials recursively
@@ -523,14 +523,13 @@ bool mjXUtil::SameVector(const T* vec1, const T* vec2, int n) {
    return false;
  }
-  bool same = true;
+  for (int i = 0; i < n; i++) {
  for (int i=0; i<n; i++) {
    if (std::abs(vec1[i] - vec2[i]) > std::numeric_limits<T>::epsilon()) {
-      same = false;
+      return false;
    }
  }
-  return same;
+  return true;
 }
 template bool mjXUtil::SameVector(const double* vec1, const double* vec2, int n);
@@ -765,6 +765,80 @@ TEST_F(ActuatorTest, ActuatorForceClamping) {
  mj_deleteModel(model);
 }
 // Apply gravity compensation via actuators
 TEST_F(ActuatorTest, ActuatorGravcomp) {
  static constexpr char xml[] = R"(
  <mujoco>
    <worldbody>
      <body gravcomp="1">
        <joint name="joint" type="slide" axis="0 0 1"
               actuatorfrcrange="-2 2" actuatorgravcomp="true"/>
        <geom type="box" size=".05 .05 .05" mass="1"/>
      </body>
    </worldbody>
    <actuator>
      <motor name="actuator" joint="joint"/>
    </actuator>
    <sensor>
      <actuatorfrc actuator="actuator"/>
      <jointactuatorfrc joint="joint"/>
    </sensor>
  </mujoco>
  )";
  mjModel* model = LoadModelFromString(xml);
  mjData* data = mj_makeData(model);
  mj_forward(model, data);
  // expect force clamping as specified in the model
  EXPECT_EQ(data->actuator_force[0], 0);
  EXPECT_EQ(data->qfrc_actuator[0], 2);
  EXPECT_EQ(data->qfrc_passive[0], 0);
  EXPECT_EQ(data->sensordata[0], 0);
  EXPECT_EQ(data->sensordata[1], 2);
  // reduce gravity so gravcomp is not clamped
  model->opt.gravity[2] = -1;
  mj_forward(model, data);
  EXPECT_EQ(data->actuator_force[0], 0);
  EXPECT_EQ(data->qfrc_actuator[0], 1);
  EXPECT_EQ(data->qfrc_passive[0], 0);
  EXPECT_EQ(data->sensordata[0], 0);
  EXPECT_EQ(data->sensordata[1], 1);
  // add control, see that it adds up
  data->ctrl[0] = 0.5;
  mj_forward(model, data);
  EXPECT_EQ(data->actuator_force[0], 0.5);
  EXPECT_EQ(data->qfrc_actuator[0], 1.5);
  EXPECT_EQ(data->qfrc_passive[0], 0);
  EXPECT_EQ(data->sensordata[0], 0.5);
  EXPECT_EQ(data->sensordata[1], 1.5);
  // add larger control, expect clamping
  data->ctrl[0] = 1.5;
  mj_forward(model, data);
  EXPECT_EQ(data->actuator_force[0], 1.5);
  EXPECT_EQ(data->qfrc_actuator[0], 2);
  EXPECT_EQ(data->qfrc_passive[0], 0);
  EXPECT_EQ(data->sensordata[0], 1.5);
  EXPECT_EQ(data->sensordata[1], 2);
  // disable actgravcomp, expect gravcomp as a passive force
  model->jnt_actgravcomp[0] = 0;
  mj_forward(model, data);
  EXPECT_EQ(data->actuator_force[0], 1.5);
  EXPECT_EQ(data->qfrc_actuator[0], 1.5);
  EXPECT_EQ(data->qfrc_passive[0], 1);
  EXPECT_EQ(data->sensordata[0], 1.5);
  EXPECT_EQ(data->sensordata[1], 1.5);
  mj_deleteData(data);
  mj_deleteModel(model);
 }
 // ----------------------- filterexact actuators -------------------------------
 using FilterExactTest = MujocoTest;
@@ -15,7 +15,10 @@
 // Tests for engine/engine_resource.c
 #include <array>
 #include <cstdint>
 #include <cstring>
 #include <ctime>
 #include <string>
 #include <gmock/gmock.h>
 #include <gtest/gtest.h>
@@ -24,6 +27,7 @@
 #include <mujoco/mujoco.h>
 #include "src/engine/engine_plugin.h"
 #include "src/engine/engine_resource.h"
 #include "src/engine/engine_util_misc.h"
 #include "test/fixture.h"
 namespace mujoco {
@@ -327,5 +331,34 @@ TEST_F(ResourceTest, NameWithInvalidPrefix) {
  ASSERT_THAT(resource, IsNull());
 }
 TEST_F(ResourceTest, OSFilesystemTimestamps) {
  time_t t;
  // some random file
  const char* const file = "engine/testdata/collision_box/boxbox_deep.xml";
  const std::string xml_path = GetTestDataFilePath(file);
  mjResource* resource = mju_openResource(xml_path.c_str(), nullptr, 0);
  mju_decodeBase64((uint8_t*) &t, resource->timestamp);
  // equal timestamps
  EXPECT_EQ(mju_isModifiedResource(resource, resource->timestamp), 0);
  std::array<char, 512> test_timestamp;
  // older resource timestamp
  t++;
  mju_encodeBase64(test_timestamp.data(), (uint8_t*) &t, sizeof(time_t));
  EXPECT_EQ(mju_isModifiedResource(resource, test_timestamp.data()), -1);
  // newer resource timestamp
  t -= 2;
  mju_encodeBase64(test_timestamp.data(), (uint8_t*) &t, sizeof(time_t));
  EXPECT_EQ(mju_isModifiedResource(resource, test_timestamp.data()), 1);
  mju_closeResource(resource);
 }
 }  // namespace
 }  // namespace mujoco
@@ -95,5 +95,38 @@ TEST_F(EngineUtilBlasTest, MjuSymmetrize) {
                               3, 3.5, 3));
 }
 TEST_F(EngineUtilBlasTest, MjuMulMat3) {
  const mjtNum mat1[9] = {
    1, 2, 3,
    4, 5, 6,
    7, 8, 9
  };
  const mjtNum mat2[9] = {
    2, 3, 4,
    5, 6, 7,
    8, 9, 10
  };
  mjtNum res1[9] = {0};
  mjtNum res2[9] = {0};
  mju_mulMatMat3(res1, mat1, mat2);
  mju_mulMatMat(res2, mat1, mat2, 3, 3, 3);
  for (int i = 0; i < 9; ++i) {
    EXPECT_EQ(res1[i], res2[i]);
  }
  mju_mulMatTMat3(res1, mat1, mat2);
  mju_mulMatTMat(res2, mat1, mat2, 3, 3, 3);
  for (int i = 0; i < 9; ++i) {
    EXPECT_EQ(res1[i], res2[i]);
  }
  mju_mulMatMatT3(res1, mat1, mat2);
  mju_mulMatMatT(res2, mat1, mat2, 3, 3, 3);
  for (int i = 0; i < 9; ++i) {
    EXPECT_EQ(res1[i], res2[i]);
  }
 }
 }  // namespace
 }  // namespace mujoco
@@ -20,6 +20,8 @@
 #include <gmock/gmock.h>
 #include <gtest/gtest.h>
 #include <mujoco/mujoco.h>
 #include "src/engine/engine_resource.h"
 #include "src/engine/engine_vfs.h"
 #include "test/fixture.h"
 namespace mujoco {
@@ -28,7 +30,7 @@ namespace {
 using ::testing::NotNull;
 using EngineVfsTest = MujocoTest;
-TEST_F(EngineVfsTest, AddFileTest) {
+TEST_F(EngineVfsTest, AddFile) {
  constexpr char path[] = "engine/testdata/actuation/";
  const std::string dir = GetTestDataFilePath(path);
  std::string file1 = "activation.xml";
@@ -81,7 +83,7 @@ TEST_F(EngineVfsTest, AddFileTest) {
  mj_deleteVFS(vfs.get());
 }
-TEST_F(EngineVfsTest, AddBufferTest) {
+TEST_F(EngineVfsTest, AddBuffer) {
  auto vfs = std::make_unique<mjVFS>();
  mj_defaultVFS(vfs.get());
  std::string buffer = "<mujoco/>";
@@ -94,5 +96,32 @@ TEST_F(EngineVfsTest, AddBufferTest) {
  mj_deleteVFS(vfs.get());
 }
 TEST_F(EngineVfsTest, Timestamps) {
  static constexpr char cube[] = R"(
  v -0.500000 -0.500000  0.500000
  v  0.500000 -0.500000  0.500000
  v -0.500000  0.500000  0.500000
  v  0.500000  0.500000  0.500000
  v -0.500000  0.500000 -0.500000
  v  0.500000  0.500000 -0.500000
  v -0.500000 -0.500000 -0.500000
  v  0.500000 -0.500000 -0.500000)";
  auto vfs = std::make_unique<mjVFS>();
  mj_defaultVFS(vfs.get());
  mj_addBufferVFS(vfs.get(), "cube.obj", cube, sizeof(cube));
  mjResource* resource = mju_openVfsResource("cube.obj", vfs.get());
  // same timestamps
  EXPECT_EQ(mju_isModifiedResource(resource, resource->timestamp), 0);
  // different timestamps
  EXPECT_EQ(mju_isModifiedResource(resource, "QQ=="), 1);
  mju_closeResource(resource);
  mj_deleteVFS(vfs.get());
 }
 }  // namespace
 }  // namespace mujoco
@@ -6,7 +6,7 @@
  (e.g. 4 consecutive ball joints is not a realistic kinematic design)
  -->
  <option viscosity="10" integrator="implicit">
-    <flag gravity="disable" contact="disable"/>
+    <flag contact="disable"/>
  </option>
  <statistic meansize=".05"/>
@@ -29,7 +29,7 @@
    commands is achievable by individual joint actuators with the specified torque limits.
    See https://mujoco.readthedocs.io/en/latest//modeling.html#actuator-force-clamping
    -->
-    <joint stiffness="1e-1" actuatorfrcrange="-1 1"/>
+    <joint armature="1e-3" damping="1e-3" stiffness="1e-2" actuatorfrcrange="-1 1" actuatorgravcomp="true"/>
    <site type="box" size=".012 .012 .012" rgba=".7 .7 .8 1"/>
  </default>
@@ -37,19 +37,19 @@
    <light pos="0 0 2"/>
    <geom type="box" size=".25 .25 .01" pos="0 0 -.01"/>
    <site name="reference" pos="0 0 .25"/>
-    <body name="arm" pos="-.25 .25 0">
+    <body name="arm" pos="-.25 .25 0" gravcomp="1">
      <joint axis="1 0 0"/>
      <joint axis="0 1 0"/>
      <geom type="box" size=".01" fromto="0 0 0 0 0 .25"/>
-      <body pos="0 0 .25">
+      <body pos="0 0 .25" gravcomp="1">
        <joint axis="0 1 0"/>
        <joint axis="0 0 1"/>
        <geom type="box" size=".01" fromto="0 0 0 .25 0 0"/>
-        <body pos=".25 0 0">
+        <body pos=".25 0 0" gravcomp="1">
          <joint axis="1 0 0"/>
          <joint axis="0 0 1"/>
          <geom type="box" size=".01" fromto="0 0 0 0 -.2 0"/>
-          <body pos="0 -.2 0">
+          <body pos="0 -.2 0" gravcomp="1">
            <joint axis="1 0 0"/>
            <joint axis="0 0 1"/>
            <joint axis="0 1 0"/>
@@ -32,8 +32,14 @@ test_model() {
      # this test can take several minutes under ASAN
      return 0
    fi
-    if [[ "$model" == */benchmark/testdata/humanoid200.xml
+    if [[ "$model" == */benchmark/testdata/humanoid200.xml ||
-        || "$model" == */engine/testdata/collision_convex/stacked_boxes.xml
+          "$model" == */engine/testdata/collision_convex/stacked_boxes.xml ||
          "$model" == */user/testdata/shark_41_ascii_gmshApp.xml ||
          "$model" == */user/testdata/shark_22_ascii_fTetWild.xml ||
          "$model" == */user/testdata/shark_22_ascii_gmshApp.xml ||
          "$model" == */user/testdata/shark_22_binary_fTetWild.xml ||
          "$model" == */user/testdata/shark_41_binary_gmshApp.xml ||
          "$model" == */user/testdata/shark_22_binary_gmshApp.xml
    ]]; then
      iterations=2
    fi
@@ -17,8 +17,13 @@
                  1.618     0      -1
                 -1.618     0       1
                 -1.618     0      -1"/>
-    <hfield name="hfield" nrow="3" ncol="3" size=".2 .2 .1 .03"/>
+    <hfield name="hfield" nrow="3" ncol="3" size=".2 .2 .03 .03"
            elevation="1 0 1
                       0 1 0
                       1 0 1"/>
    <texture builtin="gradient" height="100" rgb1="1 1 1" rgb2="0 0 0" type="skybox" width="100"/>
    <texture name="grid" type="cube" builtin="checker" width="32" height="32" rgb1=".1 .2 .3" rgb2="1 1 1"/>
    <material name="grid" texture="grid" texrepeat="1 1" texuniform="true" reflectance=".2"/>
  </asset>
  <default>
@@ -41,7 +46,7 @@
    <geom name="floor" type="plane" size="4 4 .1"/>
    <geom type="hfield" hfield="hfield" pos="-.4 .6 .05" rgba="0 0 1 1"/>
    <body name="head" pos="0 0 .7">
-      <geom type="ellipsoid" size=".2 .2 .4" rgba="1 1 0 1" density="100"/>
+      <geom type="ellipsoid" size=".2 .2 .4" density="100" material="grid"/>
      <site name="head" pos="0 0 .4" size=".1 .1 .05" type="box"/>
      <site name="anchor0" pos="0 .2 0"/>
      <site name="rf" pos="0 0 -0.41" zaxis="0 0 -1"/>
@@ -161,4 +166,13 @@
         qpos="0.0133625 -0.013799 0.659429 0.999776 0.019159 0.00902704 0.000572574 -0.00776575 0.0983289 0.999861 -0.00869796 -0.0141805 0.000912197 0.00700633 0.0930296 0.00637469 -0.00313231 0.119692 0.0051478 -0.0469067 0 -0.500224 0.300659 0.69913 1 -0.000367766 -0.000265698 -0.000109715 -0.319851 0.525628 0.702735 0.29858 0.698263 -0.0490604 -0.648746 -0.579432 0.4206 0.749601 0.900145 -0.208463 0.346664 -0.161576 -0.200033 0.300084 0.976421 0.878429 -0.00171382 0.00127086 -0.477867"
         qvel="0.508861 -0.243772 -0.327162 0.549686 1.13746 0.0282475 -0.0865243 1.06414 -0.239958 -0.532111 -0.00133789 -0.0654491 0.533148 -0.253161 0.122149 0.824764 0.723529 -0.674175 0 -0.00154509 -0.00568917 0.00479921 0.00541817 0.00115895 0.00317796 -0.160161 -0.599488 -1.38103 14.9789 -1.05454 -13.9252 -0.31223 -0.0102486 -0.405851 5.43992 -4.71514 0.114928 -0.00123758 0.000187845 -0.244109 -0.190199 0.0697975 -16.3286"/>
  </keyframe>
  <custom>
    <numeric name="numeric" data="1 2 3"/>
    <text name="text" data="abc"/>
    <tuple name="tuple">
      <element objtype="body" objname="cylinder" prm="1"/>
      <element objtype="joint" objname="hipz_0" prm="2"/>
    </tuple>
  </custom>
 </mujoco>
--- a/Show More
+++ b/Show More
`@@ -14,6 +14,6 @@ if __name__ == "__main__":`

	`exp.update_scene(d)`	`exp.update_scene(d)`

	`exp.save_scene(filetype="usd")`	`exp.save_scene(filetype="usda")`