Fix kinematics for mocap bodies with child bodies#858
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adenzler-nvidia merged 14 commits intoNov 21, 2025
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Signed-off-by: Alain Denzler <adenzler@nvidia.com>
Signed-off-by: Alain Denzler <adenzler@nvidia.com>
Signed-off-by: Alain Denzler <adenzler@nvidia.com>
Signed-off-by: Alain Denzler <adenzler@nvidia.com>
Signed-off-by: Alain Denzler <adenzler@nvidia.com>
Signed-off-by: Alain Denzler <adenzler@nvidia.com>
Signed-off-by: Alain Denzler <adenzler@nvidia.com>
Signed-off-by: Alain Denzler <adenzler@nvidia.com>
Signed-off-by: Alain Denzler <adenzler@nvidia.com>
Signed-off-by: Alain Denzler <adenzler@nvidia.com>
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confirmed that this is a bug with the MJX implementation, thanks for reporting and fixing this bug with MJWarp @adenzler-nvidia! |
thowell
reviewed
Nov 20, 2025
| xml = """ | ||
| <mujoco> | ||
| <worldbody> | ||
| <body name="mocap_parent" mocap="true" pos="0 0 0"> |
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we don't need to specify pos="0 0 0" since this is the default
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removed, thanks for the pointer.
thowell
reviewed
Nov 20, 2025
| _assert_eq(d.xpos.numpy()[0], mjd.xpos, "initial xpos") | ||
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| # Expected: child should be at mocap_pos + (1, 0, 0) relative offset | ||
| np.testing.assert_allclose(initial_child_xpos, [1.0, 0.0, 0.0], atol=1e-5) |
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can we use _assert_eq here and below?
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done, thanks,
thowell
approved these changes
Nov 20, 2025
Signed-off-by: Alain Denzler <adenzler@nvidia.com>
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The sequence of kinematics -> mocap was wrong because if a mocap body had descendant bodies, the kinematics for these bodies were calculated based on the body_pos/quat values instead of mocap_pos/mocap_quat.
I took the liberty of just fusing in the mocap update into the kinematics kernel because it made sense to me, and it looks like there is a slight edge to this performance-wise. It will definitely help for scenes with a lot of mocap bodies.