Failed to Animate Custom Robot with Lula Test Widget

Omniverse Isaac Sim
1

Isaac Sim Version

5.0.0

Operating System

Windows 11

GPU Information

  • Model: RTX A3000
  • Driver Version: 573.73

Topic Description

Detailed Description

I am trying to command my robot to different waypoints using the Test Lula Widget.

After trying to import with URDF and fail. I took the base .USD from https://omniverse-content-production.s3-us-west-2.amazonaws.com/Assets/Isaac/5.0/Isaac/Robots/UniversalRobots/ur3e/configuration/

And loaded it in Blender, I defined the URDF using Phobos and exported it.

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image846×703 130 KB

Upon loading into Isaac Sim, I have successfully loaded it as an articulation with Lula Robot Description Editor despite getting this error:

2025-10-13T14:33:47Z [17,716,658ms] [Error] [omni.physx.tensors.plugin] Pattern ‘/World/UR3E/root_joint’ did not match any rigid bodies

2025-10-13T14:33:47Z [17,716,659ms] [Error] [omni.physx.tensors.plugin] Provided pattern list did not match any articulations

And generated the corresponding .yaml and .xrdf files.

Then moving on to the Lula Test Widget I have faced the following errors:

2025-10-13T14:33:47Z [17,716,715ms] [Error] [omni.kit.app._impl] [py stderr]: AttributeError: ‘NoneType’ object has no attribute ‘is_homogeneous’

Steps to Reproduce

  1. Load URDF

  2. Press Play to find error: 2025-10-13T14:33:47Z [17,716,658ms] [Error] [omni.physx.tensors.plugin] Pattern ‘/World/UR3E/root_joint’ did not match any rigid bodies

    2025-10-13T14:33:47Z [17,716,659ms] [Error] [omni.physx.tensors.plugin] Provided pattern list did not match any articulations

  3. Go to Lula Test Widget, and load the attached .YAML as well to find next error.
    2025-10-13T14:33:47Z [17,716,715ms] [Error] [omni.kit.app._impl] [py stderr]: AttributeError: ‘NoneType’ object has no attribute ‘is_homogeneous’

And subsequent:
2025-10-13T14:35:50Z [17,840,166ms] [Error] [omni.kit.app._impl] [py stderr]: Traceback (most recent call last):
2025-10-13T14:35:50Z [17,840,166ms] [Error] [omni.kit.app._impl] [py stderr]: File “c:/isaacsim/exts/isaacsim.robot_setup.xrdf_editor/isaacsim/robot_setup/xrdf_editor/extension.py”, line 571, in _on_physics_step
2025-10-13T14:35:50Z [17,840,167ms] [Error] [omni.kit.app._impl] [py stderr]: self.articulation.initialize()
2025-10-13T14:35:50Z [17,840,167ms] [Error] [omni.kit.app._impl] [py stderr]: File “c:/isaacsim/exts/isaacsim.core.prims/isaacsim/core/prims/impl/single_articulation.py”, line 320, in initialize
2025-10-13T14:35:50Z [17,840,167ms] [Error] [omni.kit.app._impl] [py stderr]: self._articulation_view.initialize(physics_sim_view=physics_sim_view)
2025-10-13T14:35:50Z [17,840,168ms] [Error] [omni.kit.app._impl] [py stderr]: File “c:/isaacsim/exts/isaacsim.core.prims/isaacsim/core/prims/impl/articulation.py”, line 5148, in initialize
2025-10-13T14:35:50Z [17,840,169ms] [Error] [omni.kit.app._impl] [py stderr]: self._on_physics_ready(None)
2025-10-13T14:35:50Z [17,840,169ms] [Error] [omni.kit.app._impl] [py stderr]: File “c:/isaacsim/exts/isaacsim.core.prims/isaacsim/core/prims/impl/articulation.py”, line 5154, in _on_physics_ready
2025-10-13T14:35:50Z [17,840,171ms] [Error] [omni.kit.app._impl] [py stderr]: self._physics_view = simulation_view.create_articulation_view(
2025-10-13T14:35:50Z [17,840,171ms] [Error] [omni.kit.app._impl] [py stderr]: ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
2025-10-13T14:35:50Z [17,840,172ms] [Error] [omni.kit.app._impl] [py stderr]: AttributeError: ‘NoneType’ object has no attribute ‘create_articulation_view’
2025-10-13T14:36:23Z [17,872,726ms] [Warning] [isaacsim.robot_motion.lula_test_widget.controllers] Failed to compute Inverse Kinematics

Error Messages

2025-10-13T14:33:47Z [17,716,594ms] [Error] [omni.kit.app._impl] [py stderr]: Traceback (most recent call last):
2025-10-13T14:33:47Z [17,716,595ms] [Error] [omni.kit.app._impl] [py stderr]: File “c:/isaacsim/exts/isaacsim.robot_setup.xrdf_editor/isaacsim/robot_setup/xrdf_editor/extension.py”, line 571, in _on_physics_step
2025-10-13T14:33:47Z [17,716,616ms] [Error] [omni.kit.app._impl] [py stderr]: self.articulation.initialize()
2025-10-13T14:33:47Z [17,716,617ms] [Error] [omni.kit.app._impl] [py stderr]: File “c:/isaacsim/exts/isaacsim.core.prims/isaacsim/core/prims/impl/single_articulation.py”, line 320, in initialize
2025-10-13T14:33:47Z [17,716,618ms] [Error] [omni.kit.app._impl] [py stderr]: self._articulation_view.initialize(physics_sim_view=physics_sim_view)
2025-10-13T14:33:47Z [17,716,618ms] [Error] [omni.kit.app._impl] [py stderr]: File “c:/isaacsim/exts/isaacsim.core.prims/isaacsim/core/prims/impl/articulation.py”, line 5148, in initialize
2025-10-13T14:33:47Z [17,716,647ms] [Error] [omni.kit.app._impl] [py stderr]: self._on_physics_ready(None)
2025-10-13T14:33:47Z [17,716,648ms] [Error] [omni.kit.app._impl] [py stderr]: File “c:/isaacsim/exts/isaacsim.core.prims/isaacsim/core/prims/impl/articulation.py”, line 5154, in _on_physics_ready
2025-10-13T14:33:47Z [17,716,650ms] [Error] [omni.kit.app._impl] [py stderr]: self._physics_view = simulation_view.create_articulation_view(
2025-10-13T14:33:47Z [17,716,651ms] [Error] [omni.kit.app._impl] [py stderr]: ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
2025-10-13T14:33:47Z [17,716,652ms] [Error] [omni.kit.app._impl] [py stderr]: AttributeError: ‘NoneType’ object has no attribute ‘create_articulation_view’
2025-10-13T14:33:47Z [17,716,658ms] [Error] [omni.physx.tensors.plugin] Pattern ‘/World/UR3E/root_joint’ did not match any rigid bodies

2025-10-13T14:33:47Z [17,716,659ms] [Error] [omni.physx.tensors.plugin] Provided pattern list did not match any articulations

2025-10-13T14:33:47Z [17,716,660ms] [Error] [omni.kit.app._impl] [py stderr]: Traceback (most recent call last):
2025-10-13T14:33:47Z [17,716,660ms] [Error] [omni.kit.app._impl] [py stderr]: File “c:/isaacsim/exts/isaacsim.robot_setup.xrdf_editor/isaacsim/robot_setup/xrdf_editor/extension.py”, line 571, in _on_physics_step
2025-10-13T14:33:47Z [17,716,660ms] [Error] [omni.kit.app._impl] [py stderr]: self.articulation.initialize()
2025-10-13T14:33:47Z [17,716,661ms] [Error] [omni.kit.app._impl] [py stderr]: File “c:/isaacsim/exts/isaacsim.core.prims/isaacsim/core/prims/impl/single_articulation.py”, line 320, in initialize
2025-10-13T14:33:47Z [17,716,661ms] [Error] [omni.kit.app._impl] [py stderr]: self._articulation_view.initialize(physics_sim_view=physics_sim_view)
2025-10-13T14:33:47Z [17,716,663ms] [Error] [omni.kit.app._impl] [py stderr]: File “c:/isaacsim/exts/isaacsim.core.prims/isaacsim/core/prims/impl/articulation.py”, line 5148, in initialize
2025-10-13T14:33:47Z [17,716,664ms] [Error] [omni.kit.app._impl] [py stderr]: self._on_physics_ready(None)
2025-10-13T14:33:47Z [17,716,665ms] [Error] [omni.kit.app._impl] [py stderr]: File “c:/isaacsim/exts/isaacsim.core.prims/isaacsim/core/prims/impl/articulation.py”, line 5159, in _on_physics_ready
2025-10-13T14:33:47Z [17,716,667ms] [Error] [omni.kit.app._impl] [py stderr]: assert self._physics_view.is_homogeneous
2025-10-13T14:33:47Z [17,716,667ms] [Error] [omni.kit.app._impl] [py stderr]: ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
2025-10-13T14:33:47Z [17,716,667ms] [Error] [omni.kit.app._impl] [py stderr]: File “c:/isaacsim/extscache/omni.physics.tensors-107.3.18+107.3.1.wx64.r.cp311.u353/omni/physics/tensors/impl/api.py”, line 704, in is_homogeneous
2025-10-13T14:33:47Z [17,716,713ms] [Error] [omni.kit.app._impl] [py stderr]: return self._backend.is_homogeneous
2025-10-13T14:33:47Z [17,716,714ms] [Error] [omni.kit.app._impl] [py stderr]: ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
2025-10-13T14:33:47Z [17,716,715ms] [Error] [omni.kit.app._impl] [py stderr]: AttributeError: ‘NoneType’ object has no attribute ‘is_homogeneous’

Screenshots or Videos

Additional Information

What I’ve Tried

Changed the collision meshes and the spheres, tried loading different URDFs

Related Issues

(If you’re aware of any related issues or forum posts, please link them here)

Additional Context

NVIDIA_ERROR.zip (2.4 KB)

(Add any other context about the problem here)

2

I highly recommend following the official Isaac Sim robot setup tutorial. This guide walks through each step of importing, assembling, and validating a manipulator’s articulation—especially helpful for catching import or asset structure issues like those reflected in your error log. Pay particular attention to root joint/articulation naming conventions as well.

3

Hello!

We noticed that this topic hasn’t received any recent responses, so we are closing it for now to help keep the forum organized.

If you’re still experiencing this issue or have additional questions, please feel free to create a new topic with updated details. When doing so, we recommend mentioning or linking to this original topic in your new post—this helps provide context and makes it easier for others to assist you.

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