Raise not implemented for frictionloss for now. #1344

PiperOrigin-RevId: 602453907
Change-Id: I0ea506b54f96c4fadc0f29f9ed0a21b0b6a7e5d9

doc/changelog.rst

@@ -31,6 +31,7 @@ MJX
 8. Added ``mjx.ray`` which mirrors :ref:`mj_ray` for planes, spheres, capsules, boxes, and meshes.
 9. Added ``mjx.is_sparse`` which mirrors :ref:`mj_isSparse` and ``mjx.full_m`` which mirrors :ref:`mj_fullM`.
 10. Added support for specifying sparse or dense mass matrices via :ref:`option-jacobian`.
+11. Raise a not implemented error when nonzero frictionloss is present. Fixes :github:issue:`1344`.
 
 Python bindings
 ^^^^^^^^^^^^^^^

mjx/mujoco/mjx/_src/device.py

@@ -164,6 +164,9 @@ def _validate(m: mujoco.MjModel):
     if f & m.opt.enableflags:
       warnings.warn(f'Ignoring enable flag {f.name}.')
 
+  if not np.allclose(m.dof_frictionloss, 0):
+    raise NotImplementedError('dof_frictionloss is not implemented.')
+
 
 @overload
 def device_put(value: mujoco.MjData) -> types.Data:

mjx/mujoco/mjx/_src/io.py

@@ -109,6 +109,9 @@ def put_model(m: mujoco.MjModel, device=None) -> types.Model:
           f'{[mj_type(m) for m in missing]} not supported'
       )
 
+  if not np.allclose(m.dof_frictionloss, 0):
+    raise NotImplementedError('dof_frictionloss is not implemented.')
+
   opt = _put_option(m.opt, device=device)
   stat = _put_statistic(m.stat, device=device)
 

mjx/mujoco/mjx/test_data/shadow_hand/right_hand.xml

@@ -12,7 +12,7 @@
   <default>
     <default class="right_hand">
       <mesh scale="0.001 0.001 0.001"/>
-      <joint axis="1 0 0" damping="0.05" armature="0.0002" frictionloss="0.01"/>
+      <joint axis="1 0 0" damping="0.05" armature="0.0002"/>
       <position forcerange="-1 1"/>
 
       <default class="wrist">