Add mj_fwdKinematics and a table improving documentation of the MuJoCo computation pipeline structure.
PiperOrigin-RevId: 838768130 Change-Id: I1a22d5cdca7db704ba4cea1667fcbecb16b87005
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Yuval Tassa
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Copybara-Service
Copybara-Service
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@@ -715,6 +715,15 @@ Components
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These are components of the simulation pipeline, called internally from :ref:`mj_step`, :ref:`mj_forward` and
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:ref:`mj_inverse`. It is unlikely that the user will need to call them.
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.. _mj_fwdKinematics:
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`mj_fwdKinematics <#mj_fwdKinematics>`__
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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.. mujoco-include:: mj_fwdKinematics
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Run all kinematics-like computations (kinematics, comPos, camlight, flex, tendon).
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.. _mj_fwdPosition:
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`mj_fwdPosition <#mj_fwdPosition>`__
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@@ -18,6 +18,8 @@ General
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flex object is similar to the "trilinear" option, but it includes curved deformations.
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- Raise an error if there are name collisions also during parsing.
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- Increase Windows stack size to 16MB to enable models with deep nested body hierarchies.
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- Added a new pipeline component function :ref:`mj_fwdKinematics` that combines all kinematics-like sub-components.
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Relatedly, added a clarifying table at the top of the :ref:`Simulation Pipeline<Pipeline>` chapter.
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- Added a new :ref:`mj_extractState` function that allows a subset of a state that was previously returned by
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:ref:`mj_getState` to be extracted without having to be written back into ``mjData`` first.
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- Added a new :ref:`mj_copyState` function that copies state components from one ``mjData`` to another.
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@@ -1741,12 +1741,32 @@ Top level
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- The top-level function :ref:`mj_step` invokes the entire sequence of computations below.
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- :ref:`mj_forward` invokes only stages **2-22**, computing the continuous-time forward dynamics, ending with the
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acceleration ``mjData.qacc``.
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- :ref:`mj_step1` invokes stages **1-18** and :ref:`mj_step2` invokes stages **19-25**, breaking :ref:`mj_step` into two
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- :ref:`mj_step1` invokes stages **1-19** and :ref:`mj_step2` invokes stages **20-26**, breaking :ref:`mj_step` into two
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distinct phases. This allows the user to write controllers that depend on quantities derived from the positions and
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velocities (but not forces, since those have not yet been computed). Note that the :ref:`mj_step1` → :ref:`mj_step2`
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pipeline does not support the Runge Kutta integrator.
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- :ref:`mj_fwdPosition` invokes stages **2-11**, the position-dependent part of the pipeline.
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.. the table below was created and is editable in tablesgenerator.com
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.. table:: Breakdown of the forward dynamic pipeline
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:class: small-centered no-stripes
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+-------------------------+----------------------------------------------------------------------------------------------------------------------+
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| top-level functions | :ref:`mj_step` |
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| +------------------------------------------------------------------------------------+---------------------------------+
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| | :ref:`mj_step1` | :ref:`mj_step2` |
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| +------------------------------------------------------------------------------------+-------------+-------+-----------+
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| | :ref:`mj_forward` | | |
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+-------------------------+---+----------------------------------------------+----+-----------------------+----+-------------+-------+-----------+
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| component / description | | :ref:`mj_fwdPosition` | | :ref:`mj_fwdVelocity` | | force / acc | | integrate |
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| +---+-------------------------+--------------------+----+-----------------------+----+-------------+-------+-----------+
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| | | :ref:`mj_fwdKinematics` | inertia, collision | | | | | | |
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+-------------------------+---+-------------------------+--------------------+----+-----------------------+----+-------------+-------+-----------+
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| stage | 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 |
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+-------------------------+---+-------------------------+--------------------+----+-----------------------+----+-------------+-------+-----------+
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.. _piStages:
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Stages
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@@ -1796,24 +1816,28 @@ dependence structure of the pipeline, the actual dependence is on both ``qpos``
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17. Compute the reference constraint acceleration: :ref:`mj_referenceConstraint`
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18. Compute the vector of Coriolis, centrifugal and gravitational forces: :ref:`mj_rne`
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Control callback
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''''''''''''''''
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19. Invoke the user-defined control callback if defined: :ref:`mjcb_control`
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Force/acceleration
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''''''''''''''''''
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The stages below compute quantities that depend on :ref:`user inputs<geInput>`. Due to the sequential nature
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of the pipeline, the actual dependence is on the entire :ref:`integration state<geIntegrationState>`.
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19. Compute the actuator forces and activation dynamics if defined: :ref:`mj_fwdActuation`
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20. Compute the joint acceleration resulting from all forces except for the (still unknown) constraint forces:
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20. Compute the actuator forces and activation dynamics if defined: :ref:`mj_fwdActuation`
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21. Compute the joint acceleration resulting from all forces except for the (still unknown) constraint forces:
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:ref:`mj_fwdAcceleration`
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21. Compute the constraint forces with the selected solver, and update the joint acceleration so as to account for the
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22. Compute the constraint forces with the selected solver, and update the joint acceleration so as to account for the
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constraint forces. This yields the vector ``mjData.qacc`` which is the main output of forward dynamics:
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:ref:`mj_fwdConstraint`
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22. Compute sensor data that depends on force and acceleration if enabled
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23. Compute sensor data that depends on force and acceleration if enabled
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(if required by sensors, call :ref:`mj_rnePostConstraint`): :ref:`mj_sensorAcc`
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23. Check the acceleration for invalid or unacceptably large real values. If divergence is detected, the state is
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24. Check the acceleration for invalid or unacceptably large real values. If divergence is detected, the state is
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automatically reset and the corresponding warning is raised: :ref:`mj_checkAcc`
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24. Compare the results of forward and inverse dynamics, so as to diagnose poor solver convergence in the forward
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25. Compare the results of forward and inverse dynamics, so as to diagnose poor solver convergence in the forward
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dynamics. This is an optional step, and is performed only when enabled: :ref:`mj_compareFwdInv`
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25. Advance the simulation state by one time step, using the selected integrator. Note that the Runge-Kutta integrator
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26. Advance the simulation state by one time step, using the selected integrator. Note that the Runge-Kutta integrator
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repeats the above sequence three more times, except for the optional computations which are performed only once:
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one of :ref:`mj_Euler`, :ref:`mj_RungeKutta`, :ref:`mj_implicit`
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@@ -3132,6 +3132,7 @@ int mj_printSchema(const char* filename, char* buffer, int buffer_sz,
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void mj_printScene(const mjvScene* s, const char* filename);
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void mj_printFormattedScene(const mjvScene* s, const char* filename,
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const char* float_format);
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void mj_fwdKinematics(const mjModel* m, mjData* d);
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void mj_fwdPosition(const mjModel* m, mjData* d);
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void mj_fwdVelocity(const mjModel* m, mjData* d);
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void mj_fwdActuation(const mjModel* m, mjData* d);
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