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Use the string (rot:lin) in mjdata.h to clarify where 6D motion vectors use the Featherstone convention. Also add clarifying text to the appropriate note in the documentation.

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Fixes #982.

PiperOrigin-RevId: 589556339
Change-Id: I3e7ff185a089715a386694321d4b89d09d481cf9
This commit is contained in:
Yuval Tassa
2023-12-10 03:26:49 -08:00
committed by Copybara-Service
parent b22919543d
commit 1885d518eb
4 changed files with 12 additions and 12 deletions
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doc/APIreference/APItypes.rst
+3 -3
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@@ -1219,9 +1219,9 @@ a frame at the center-of-mass of the local kinematic subtree (``mjData.subtree_c
This choice increases the precision of kinematic computations for mechanisms that are distant from the global origin.
``cdof``:
These 6D motion vectors describe the instantaneous axis of a degree-of-freedom and are used by all Jacobian functions.
Therefore, the minimal computation required for analytic Jacobians is :ref:`mj_kinematics` followed by
:ref:`mj_comPos`.
These 6D motion vectors (3 rotation, 3 translation) describe the instantaneous axis of a degree-of-freedom and are
used by all Jacobian functions. The minimal computation required for analytic Jacobians is :ref:`mj_kinematics`
followed by :ref:`mj_comPos`.
``cinert``:
These 10-vectors describe the inertial properties of a body in the c-frame and are used by the Composite Rigid Body
doc/includes/references.h
+3 -3
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@@ -237,7 +237,7 @@ struct mjData_ {
// computed by mj_fwdPosition/mj_comPos
mjtNum* subtree_com; // center of mass of each subtree (nbody x 3)
mjtNum* cdof; // com-based motion axis of each dof (nv x 6)
mjtNum* cdof; // com-based motion axis of each dof (rot:lin) (nv x 6)
mjtNum* cinert; // com-based body inertia and mass (nbody x 10)
// computed by mj_fwdPosition/mj_flex
@@ -285,8 +285,8 @@ struct mjData_ {
mjtNum* actuator_velocity; // actuator velocities (nu x 1)
// computed by mj_fwdVelocity/mj_comVel
mjtNum* cvel; // com-based velocity [3D rot; 3D tran] (nbody x 6)
mjtNum* cdof_dot; // time-derivative of cdof (nv x 6)
mjtNum* cvel; // com-based velocity (rot:lin) (nbody x 6)
mjtNum* cdof_dot; // time-derivative of cdof (rot:lin) (nv x 6)
// computed by mj_fwdVelocity/mj_rne (without acceleration)
mjtNum* qfrc_bias; // C(qpos,qvel) (nv x 1)
include/mujoco/mjdata.h
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@@ -265,7 +265,7 @@ struct mjData_ {
// computed by mj_fwdPosition/mj_comPos
mjtNum* subtree_com; // center of mass of each subtree (nbody x 3)
mjtNum* cdof; // com-based motion axis of each dof (nv x 6)
mjtNum* cdof; // com-based motion axis of each dof (rot:lin) (nv x 6)
mjtNum* cinert; // com-based body inertia and mass (nbody x 10)
// computed by mj_fwdPosition/mj_flex
@@ -313,8 +313,8 @@ struct mjData_ {
mjtNum* actuator_velocity; // actuator velocities (nu x 1)
// computed by mj_fwdVelocity/mj_comVel
mjtNum* cvel; // com-based velocity [3D rot; 3D tran] (nbody x 6)
mjtNum* cdof_dot; // time-derivative of cdof (nv x 6)
mjtNum* cvel; // com-based velocity (rot:lin) (nbody x 6)
mjtNum* cdof_dot; // time-derivative of cdof (rot:lin) (nv x 6)
// computed by mj_fwdVelocity/mj_rne (without acceleration)
mjtNum* qfrc_bias; // C(qpos,qvel) (nv x 1)
introspect/structs.py
+3 -3
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@@ -4493,7 +4493,7 @@ STRUCTS: Mapping[str, StructDecl] = dict([
type=PointerType(
inner_type=ValueType(name='mjtNum'),
),
doc='com-based motion axis of each dof (nv x 6)', # pylint: disable=line-too-long
doc='com-based motion axis of each dof (rot:lin) (nv x 6)', # pylint: disable=line-too-long
),
StructFieldDecl(
name='cinert',
@@ -4703,14 +4703,14 @@ STRUCTS: Mapping[str, StructDecl] = dict([
type=PointerType(
inner_type=ValueType(name='mjtNum'),
),
doc='com-based velocity [3D rot; 3D tran] (nbody x 6)', # pylint: disable=line-too-long
doc='com-based velocity (rot:lin) (nbody x 6)', # pylint: disable=line-too-long
),
StructFieldDecl(
name='cdof_dot',
type=PointerType(
inner_type=ValueType(name='mjtNum'),
),
doc='time-derivative of cdof (nv x 6)', # pylint: disable=line-too-long
doc='time-derivative of cdof (rot:lin) (nv x 6)', # pylint: disable=line-too-long
),
StructFieldDecl(
name='qfrc_bias',