Add documentation for MJX API

PiperOrigin-RevId: 860108133
Change-Id: I85469efcfe49d320ef8b89c9d174f33499a22b31

.readthedocs.yml

@@ -18,6 +18,7 @@ build:
       - asdf global uv latest
       - uv venv $READTHEDOCS_VIRTUALENV_PATH
       - UV_PROJECT_ENVIRONMENT=$READTHEDOCS_VIRTUALENV_PATH uv pip install -r doc/requirements.txt
+      - UV_PROJECT_ENVIRONMENT=$READTHEDOCS_VIRTUALENV_PATH uv pip install mujoco mujoco-mjx
       # replace mujoco.mjx.third_party.mujoco_warp import paths with mujoco_warp
       - |
         find mjx/mujoco/mjx/third_party/mujoco_warp -type f -exec sed -i 's/mujoco\.mjx\.third_party\.mujoco_warp/mujoco_warp/g' {} \;

doc/conf.py

@@ -78,6 +78,33 @@ add_module_names = False
 toc_object_entries_show_parents = 'hide'
 default_role = 'literal'
 
+
+# Suppress warnings from docstrings with RST formatting issues
+def setup(app):
+  import logging
+
+  class SphinxWarningFilter(logging.Filter):
+
+    def filter(self, record):
+      msg = record.getMessage()
+      # e.g. qpos0: qpos values at default pose (*, nq)
+      if 'Inline emphasis start-string' in msg:
+        return False
+      # e.g. see `name` for details
+      if 'Inline interpreted text' in msg:
+        return False
+      # e.g. multi-line definition without trailing blank line
+      if 'Definition list ends without a blank line' in msg:
+        return False
+      # e.g. mjsactuator_ reference in C++ docstrings
+      if 'Unknown target name' in msg:
+        return False
+      return True
+
+  for handler in logging.getLogger('sphinx').handlers:
+    handler.addFilter(SphinxWarningFilter())
+
+
 # GitHub-related options
 github_username = 'google-deepmind'
 github_repository = 'mujoco'

doc/mjx.rst

@@ -4,6 +4,11 @@
 MuJoCo XLA (MJX)
 ================
 
+.. toctree::
+    :hidden:
+
+    API <mjx_api.rst>
+
 Starting with version 3.0.0, MuJoCo includes MuJoCo XLA (MJX) under the
 `mjx <https://github.com/google-deepmind/mujoco/tree/main/mjx>`__ directory.  MJX allows MuJoCo to run on compute
 hardware supported by the `XLA <https://www.tensorflow.org/xla>`__ compiler via the

doc/mjx_api.rst

@@ -0,0 +1,44 @@
+MJX API
+=======
+
+.. automodule:: mujoco.mjx
+  :members:
+  :imported-members:
+  :special-members: False
+  :private-members: False
+  :exclude-members:
+      __init__,
+      __format__,
+      __new__,
+      __eq__,
+      __hash__,
+      __repr__,
+      __weakref__,
+      __or__,
+      __and__,
+      __xor__,
+      __ror__,
+      __rand__,
+      __rxor__,
+      __invert__,
+      __delattr__,
+      __setattr__,
+      __getattr__,
+      __getattribute__,
+      __reduce__,
+      __reduce_ex__,
+      __sizeof__,
+      __str__,
+      __module__,
+      __doc__,
+      __dict__,
+      __class__,
+      __le__,
+      __lt__,
+      __ge__,
+      __gt__,
+      __ne__,
+      __bool__,
+      __init_subclass__,
+      replace,
+

mjx/mujoco/mjx/__init__.py

@@ -14,6 +14,12 @@
 # ==============================================================================
 """Public API for MJX."""
 
+# isort: off
+from mujoco.mjx._src.forward import step
+from mujoco.mjx._src.types import Model
+from mujoco.mjx._src.types import Data
+# isort: on
+
 # pylint:disable=g-importing-member
 from mujoco.mjx._src.collision_driver import collision
 from mujoco.mjx._src.constraint import make_constraint
@@ -26,7 +32,6 @@ from mujoco.mjx._src.forward import fwd_position
 from mujoco.mjx._src.forward import fwd_velocity
 from mujoco.mjx._src.forward import implicit
 from mujoco.mjx._src.forward import rungekutta4
-from mujoco.mjx._src.forward import step
 from mujoco.mjx._src.inverse import inverse
 from mujoco.mjx._src.io import get_data
 from mujoco.mjx._src.io import get_data_into

mjx/mujoco/mjx/_src/ray.py

@@ -251,8 +251,8 @@ def ray(
     bodyexclude: ignore geoms on specified body id or sequence of body ids
 
   Returns:
-    dist: distance from ray origin to geom surface (or -1.0 for no intersection)
+    Distance from ray origin to geom surface (or -1.0 for no intersection) and
-    id: id of intersected geom (or -1 for no intersection)
+    id of intersected geom (or -1 for no intersection)
   """
 
   dists, ids = [], []

mjx/mujoco/mjx/_src/types.py

@@ -49,7 +49,7 @@ class Impl(enum.Enum):
 class DisableBit(enum.IntFlag):
   """Disable default feature bitflags.
 
-  Members:
+  Attributes:
     CONSTRAINT:   entire constraint solver
     EQUALITY:     equality constraints
     FRICTIONLOSS: joint and tendon frictionloss constraints
@@ -86,7 +86,7 @@ class DisableBit(enum.IntFlag):
 class EnableBit(enum.IntFlag):
   """Enable optional feature bitflags.
 
-  Members:
+  Attributes:
     INVDISCRETE: discrete-time inverse dynamics
   """
 
@@ -100,7 +100,7 @@ class EnableBit(enum.IntFlag):
 class JointType(enum.IntEnum):
   """Type of degree of freedom.
 
-  Members:
+  Attributes:
     FREE:  global position and orientation (quat)       (7,)
     BALL:  orientation (quat) relative to parent        (4,)
     SLIDE: sliding distance along body-fixed axis       (1,)
@@ -122,7 +122,7 @@ class JointType(enum.IntEnum):
 class IntegratorType(enum.IntEnum):
   """Integrator mode.
 
-  Members:
+  Attributes:
     EULER: semi-implicit Euler
     RK4: 4th-order Runge Kutta
     IMPLICITFAST: implicit in velocity, no rne derivative
@@ -137,7 +137,7 @@ class IntegratorType(enum.IntEnum):
 class GeomType(enum.IntEnum):
   """Type of geometry.
 
-  Members:
+  Attributes:
     PLANE: plane
     HFIELD: height field
     SPHERE: sphere
@@ -163,7 +163,7 @@ class GeomType(enum.IntEnum):
 class ConvexMesh(PyTreeNode):
   """Geom properties for convex meshes.
 
-  Members:
+  Attributes:
     vert: vertices of the convex mesh
     face: faces of the convex mesh
     face_normal: normal vectors for the faces
@@ -181,7 +181,7 @@ class ConvexMesh(PyTreeNode):
 class ConeType(enum.IntEnum):
   """Type of friction cone.
 
-  Members:
+  Attributes:
     PYRAMIDAL: pyramidal
     ELLIPTIC: elliptic
   """
@@ -193,7 +193,7 @@ class ConeType(enum.IntEnum):
 class JacobianType(enum.IntEnum):
   """Type of constraint Jacobian.
 
-  Members:
+  Attributes:
     DENSE: dense
     SPARSE: sparse
     AUTO: sparse if nv>60 and device is TPU, dense otherwise
@@ -207,7 +207,7 @@ class JacobianType(enum.IntEnum):
 class SolverType(enum.IntEnum):
   """Constraint solver algorithm.
 
-  Members:
+  Attributes:
     CG: Conjugate gradient (primal)
     NEWTON: Newton (primal)
   """
@@ -220,7 +220,7 @@ class SolverType(enum.IntEnum):
 class EqType(enum.IntEnum):
   """Type of equality constraint.
 
-  Members:
+  Attributes:
     CONNECT: connect two bodies at a point (ball joint)
     WELD: fix relative position and orientation of two bodies
     JOINT: couple the values of two scalar joints with cubic
@@ -237,7 +237,7 @@ class EqType(enum.IntEnum):
 class WrapType(enum.IntEnum):
   """Type of tendon wrap object.
 
-  Members:
+  Attributes:
     JOINT: constant moment arm
     PULLEY: pulley used to split tendon
     SITE: pass through site
@@ -255,7 +255,7 @@ class WrapType(enum.IntEnum):
 class TrnType(enum.IntEnum):
   """Type of actuator transmission.
 
-  Members:
+  Attributes:
     JOINT: force on joint
     JOINTINPARENT: force on joint, expressed in parent frame
     TENDON: force on tendon
@@ -272,7 +272,7 @@ class TrnType(enum.IntEnum):
 class DynType(enum.IntEnum):
   """Type of actuator dynamics.
 
-  Members:
+  Attributes:
     NONE: no internal dynamics; ctrl specifies force
     INTEGRATOR: integrator: da/dt = u
     FILTER: linear filter: da/dt = (u-a) / tau
@@ -291,7 +291,7 @@ class DynType(enum.IntEnum):
 class GainType(enum.IntEnum):
   """Type of actuator gain.
 
-  Members:
+  Attributes:
     FIXED: fixed gain
     AFFINE: const + kp*length + kv*velocity
     MUSCLE: muscle FLV curve computed by muscle_gain
@@ -306,7 +306,7 @@ class GainType(enum.IntEnum):
 class BiasType(enum.IntEnum):
   """Type of actuator bias.
 
-  Members:
+  Attributes:
     NONE: no bias
     AFFINE: const + kp*length + kv*velocity
     MUSCLE: muscle passive force computed by muscle_bias
@@ -321,7 +321,7 @@ class BiasType(enum.IntEnum):
 class ConstraintType(enum.IntEnum):
   """Type of constraint.
 
-  Members:
+  Attributes:
     EQUALITY: equality constraint
     LIMIT_JOINT: joint limit
     LIMIT_TENDON: tendon limit
@@ -342,7 +342,7 @@ class ConstraintType(enum.IntEnum):
 class CamLightType(enum.IntEnum):
   """Type of camera light.
 
-  Members:
+  Attributes:
     FIXED: pos and rot fixed in body
     TRACK: pos tracks body, rot fixed in global
     TRACKCOM: pos tracks subtree com, rot fixed in body
@@ -360,7 +360,7 @@ class CamLightType(enum.IntEnum):
 class SensorType(enum.IntEnum):
   """Type of sensor.
 
-  Members:
+  Attributes:
     MAGNETOMETER: magnetometer
     CAMPROJECTION: camera projection
     RANGEFINDER: rangefinder
@@ -436,7 +436,7 @@ class SensorType(enum.IntEnum):
 class ObjType(PyTreeNode):
   """Type of object.
 
-  Members:
+  Attributes:
     UNKNOWN: unknown object type
     BODY: body
     XBODY: body, used to access regular frame instead of i-frame
@@ -673,7 +673,57 @@ class ModelJAX(PyTreeNode):
 
 
 class Model(PyTreeNode):
-  """Static model of the scene that remains unchanged with each physics step."""
+  """Static model of the scene that remains unchanged with each physics step.
+
+  Attributes:
+    nq: number of generalized coordinates
+    nv: number of degrees of freedom
+    nu: number of actuators/controls
+    na: number of activation states
+    nbody: number of bodies
+    njnt: number of joints
+    ngeom: number of geoms
+    nsite: number of sites
+    ncam: number of cameras
+    nlight: number of lights
+    nmesh: number of meshes
+    nmeshvert: number of vertices for all meshes
+    nmeshnormal: number of normals in all meshes
+    nmeshtexcoord: number of texcoords in all meshes
+    nmeshface: number of faces for all meshes
+    nmeshgraph: number of ints in mesh auxiliary data
+    nmeshpoly: number of polygons in all meshes
+    nmeshpolyvert: number of vertices in all polygons
+    nmeshpolymap: number of polygons in vertex map
+    nhfield: number of heightfields
+    nhfielddata: size of elevation data
+    ntex: number of textures
+    ntexdata: size of texture data
+    nmat: number of materials
+    npair: number of predefined geom pairs
+    nexclude: number of excluded geom pairs
+    neq: number of equality constraints
+    ntendon: number of tendons
+    nwrap: number of wrap objects in all tendon paths
+    nsensor: number of sensors
+    nnumeric: number of numeric custom fields
+    ntuple: number of tuple custom fields
+    nkey: number of keyframes
+    nmocap: number of mocap bodies
+    nM: number of non-zeros in sparse inertia matrix
+    nB: number of non-zeros in B matrix
+    nC: number of non-zeros in C matrix
+    nD: number of non-zeros in D matrix
+    nJmom: number of non-zeros in Jacobian momentum matrix
+    ngravcomp: number of bodies with nonzero gravcomp
+    nuserdata: number of elements in userdata
+    nsensordata: number of elements in sensor data vector
+    npluginstate: number of plugin state values
+    opt: physics options
+    stat: model statistics
+    qpos0: qpos values at default pose
+    qpos_spring: reference pose for springs
+  """
 
   nq: int
   nv: int
@@ -1149,7 +1199,55 @@ class DataJAX(PyTreeNode):
 
 
 class Data(PyTreeNode):
-  """Dynamic state that updates each step."""
+  """Dynamic state that updates each step.
+
+  Attributes:
+    time: simulation time
+    qpos: position
+    qvel: velocity
+    act: actuator activation
+    qacc_warmstart: warm start for solver
+    plugin_state: plugin state values
+    ctrl: control input
+    qfrc_applied: applied generalized force
+    xfrc_applied: applied Cartesian force/torque
+    eq_active: enable/disable equality constraints
+    mocap_pos: positions of mocap bodies
+    mocap_quat: orientations of mocap bodies
+    qacc: acceleration
+    act_dot: time-derivative of actuator activation
+    userdata: user data
+    sensordata: sensor data output
+    xpos: Cartesian position of body frame
+    xquat: Cartesian orientation of body frame
+    xmat: rotation matrix of body frame
+    xipos: Cartesian position of body com
+    ximat: rotation matrix of body inertia
+    xanchor: Cartesian position of joint anchor
+    xaxis: Cartesian joint axis
+    ten_length: tendon lengths
+    geom_xpos: Cartesian position of geoms
+    geom_xmat: rotation matrix of geoms
+    site_xpos: Cartesian position of sites
+    site_xmat: rotation matrix of sites
+    cam_xpos: camera positions
+    cam_xmat: camera rotation matrices
+    subtree_com: com of each subtree
+    cvel: center of mass based velocity
+    cdof: center of mass based jacobian
+    cdof_dot: time-derivative of cdof
+    qfrc_bias: C(qpos,qvel)
+    qfrc_gravcomp: gravity compensation term
+    qfrc_fluid: fluid drag and buoyancy forces
+    qfrc_passive: passive force
+    qfrc_actuator: actuator force
+    actuator_force: actuator force in actuation space
+    actuator_length: actuator lengths
+    qfrc_smooth: smooth dynamics force
+    qacc_smooth: acceleration without constraints
+    qfrc_constraint: constraint force
+    qfrc_inverse: net external force for inverse dynamics
+  """
 
   # global properties:
   time: jax.Array