# How do I fix it? **URL:** \ **Category:** Isaac Sim\ **Created:** [January 29, 2024, 9:08am UTC](https://forums.developer.nvidia.com/t/how-do-i-fix-it/280450 "2024-01-29T09:08:07Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![1878720579](https://developer.download.nvidia.com/images/forums/profile-default-devtalk-84.png) [@1878720579](https://forums.developer.nvidia.com/u/1878720579)\ **Post date:** [January 29, 2024, 9:08am UTC](https://forums.developer.nvidia.com/t/how-do-i-fix-it/280450/1 "2024-01-29T09:08:07Z")
from omni.isaac.kit import SimulationApp simulation\_app = SimulationApp({“headless”: False}) import omni.isaac.core.utils.stage as stage\_utils from omni.isaac.core.utils.nucleus import get\_assets\_root\_path from omni.isaac.core import World from omni.isaac.core.utils.types import ArticulationAction from omni.isaac.core.articulations.articulation import Articulation my\_world = World(stage\_units\_in\_meters=1.0) my\_world.scene.add\_default\_ground\_plane() usd\_path = “/home/user/Downloads/assets/robot/shadow\_hand\_description/xarm\_shadow/xarm\_shadow.usd” prim\_path=“/xarm\_shadow” stage\_utils.add\_reference\_to\_stage(usd\_path=usd\_path, prim\_path=prim\_path) xarm\_shadow = Articulation(prim\_path=prim\_path,name = “xarm\_shadow”) xarm\_shadow = my\_world.scene.add(xarm\_shadow) my\_world.reset() i = 0 while simulation\_app.is\_running(): my\_world.step(render=True) if my\_world.is\_playing(): i += 1 simulation\_app.close() Traceback (most recent call last): File “/home/user/.local/share/ov/pkg/isaac\_sim-2023.1.0-hotfix.1/xarm\_shadow/xarm\_shadow.py”, line 19, in my\_world.reset() File “/home/user/.local/share/ov/pkg/isaac\_sim-2023.1.0-hotfix.1/exts/omni.isaac.core/omni/isaac/core/world/world.py”, line 283, in reset self.\_scene.\_finalize(self.physics\_sim\_view) File “/home/user/.local/share/ov/pkg/isaac\_sim-2023.1.0-hotfix.1/exts/omni.isaac.core/omni/isaac/core/scenes/scene.py”, line 318, in \_finalize articulated\_system.initialize(physics\_sim\_view) File “/home/user/.local/share/ov/pkg/isaac\_sim-2023.1.0-hotfix.1/exts/omni.isaac.core/omni/isaac/core/articulations/articulation.py”, line 164, in initialize self.\_articulation\_view.initialize(physics\_sim\_view=physics\_sim\_view) File “/home/user/.local/share/ov/pkg/isaac\_sim-2023.1.0-hotfix.1/exts/omni.isaac.core/omni/isaac/core/articulations/articulation\_view.py”, line 204, in initialize assert self.\_physics\_view.is\_homogeneous File “/home/user/.local/share/ov/pkg/isaac\_sim-2023.1.0-hotfix.1/extsPhysics/omni.physics.tensors-105.1.10-5.1/omni/physics/tensors/impl/api.py”, line 167, in is\_homogeneous return self.\_backend.is\_homogeneous AttributeError: ‘NoneType’ object has no attribute ‘is\_homogeneous’ How do I fix it? And I follow the tutorial"import URDF" and encounter the issue. ---
**Author:** ![1878720579](https://developer.download.nvidia.com/images/forums/profile-default-devtalk-84.png) [@1878720579](https://forums.developer.nvidia.com/u/1878720579)\ **Post date:** [January 29, 2024, 11:18am UTC](https://forums.developer.nvidia.com/t/how-do-i-fix-it/280450/2 "2024-01-29T11:18:49Z")
![Screenshot from 2024-01-29 19-15-09](https://global.discourse-cdn.com/nvidia/original/4X/3/1/3/313411d253cc230fc77ae314b89a8be263f1c963.jpeg) How do I make the “xarm7” as a “articulation”? ---
**Author:** ![1878720579](https://developer.download.nvidia.com/images/forums/profile-default-devtalk-84.png) [@1878720579](https://forums.developer.nvidia.com/u/1878720579)\ **Post date:** [January 30, 2024, 7:53am UTC](https://forums.developer.nvidia.com/t/how-do-i-fix-it/280450/3 "2024-01-30T07:53:52Z")
Can you help me solve this problem? ---
**Author:** ![rthaker](https://sea2.discourse-cdn.com/nvidia/user_avatar/forums.developer.nvidia.com/rthaker/32/171374_2.png) [@rthaker](https://forums.developer.nvidia.com/u/rthaker)\ **Post date:** [January 30, 2024, 11:06pm UTC](https://forums.developer.nvidia.com/t/how-do-i-fix-it/280450/4 "2024-01-30T23:06:36Z")
Hi @1878720579 - Here’s the snippet of how to add articulation ![image](https://global.discourse-cdn.com/nvidia/original/4X/b/1/8/b18eed85deeb8f9f47785e822fb73fd069ba8080.png) Here’s the doc link: [5.5. Rigging Robots — Omniverse IsaacSim latest documentation](https://docs.omniverse.nvidia.com/isaacsim/latest/advanced_tutorials/tutorial_advanced_rigging_robot.html) ---
**Author:** ![1878720579](https://developer.download.nvidia.com/images/forums/profile-default-devtalk-84.png) [@1878720579](https://forums.developer.nvidia.com/u/1878720579)\ **Post date:** [January 31, 2024, 7:13am UTC](https://forums.developer.nvidia.com/t/how-do-i-fix-it/280450/5 "2024-01-31T07:13:35Z")
I don’t think that can solve my problem. The importer carry over joint information. ![Screenshot from 2024-01-31 14-59-24](https://global.discourse-cdn.com/nvidia/original/4X/d/c/2/dc21cdfb30c6f7e5a41f7f18df759069a48d1ad5.jpeg) I use the "xarm\_shadow.urdf"URDF files as follows: [shadow\_hand\_description.zip](https://forums.developer.nvidia.com/uploads/short-url/xVOjRHIjqm4cL63TJaePcYDXchT.zip) (7.0 MB) I follow the turtorial “import urdf” and transform it to the USD. from omni.isaac.kit import SimulationApp simulation\_app = SimulationApp({“headless”: False}) import omni.isaac.core.utils.stage as stage\_utils from omni.isaac.core.utils.nucleus import get\_assets\_root\_path from omni.isaac.core import World from omni.isaac.core.utils.types import ArticulationAction from omni.isaac.core.articulations.articulation import Articulation my\_world = World(stage\_units\_in\_meters=1.0) usd\_path = “/home/user/Downloads/assets/robot/shadow\_hand\_description/xarm\_shadow/xarm\_shadow.usd” prim\_path = “/xarm\_shadow” stage\_utils.add\_reference\_to\_stage(usd\_path=usd\_path,prim\_path=prim\_path) xarm\_shadow = Articulation(prim\_path=“/xarm\_shadow/link\_base”,name = “xarm\_shadow”) xarm\_shadow = my\_world.scene.add(xarm\_shadow) my\_world.reset() print(xarm\_shadow.num\_dof) i = 0 while simulation\_app.is\_running(): my\_world.step(render=True) if my\_world.is\_playing(): i += 1 simulation\_app.close() I found when the prim path is “/xarm\_shadow/link\_base”, the “Articulation” is work. I don’t understamd. Why? ---
**Author:** ![rgasoto](https://sea2.discourse-cdn.com/nvidia/user_avatar/forums.developer.nvidia.com/rgasoto/32/21824_2.png) [@rgasoto](https://forums.developer.nvidia.com/u/rgasoto)\ **Post date:** [February 8, 2024, 10:52pm UTC](https://forums.developer.nvidia.com/t/how-do-i-fix-it/280450/8 "2024-02-08T22:52:37Z")
> [@1878720579](#): > > prim\_path=“/xarm\_shadow” your prim path here needs to point to the articulation root - When you change it to the path as listed below you selected the prim that contains the ARticulation Root API, and that’s why making that change makes it work > [@1878720579](#): > > xarm\_shadow = Articulation(prim\_path=“/xarm\_shadow/link\_base”,name = “xarm\_shadow”) ---
**Author:** ![rodineye](https://developer.download.nvidia.com/images/forums/profile-default-devtalk-84.png) [@rodineye](https://forums.developer.nvidia.com/u/rodineye)\ **Post date:** [February 18, 2024, 6:55am UTC](https://forums.developer.nvidia.com/t/how-do-i-fix-it/280450/9 "2024-02-18T06:55:42Z")
if you use 2022.2.1 urdf importer, the articulation root path will be “/xarm\_shadow”, if you use 2023.1.1 urdf importer, the articulation root path will be “/xarm\_shadow/link\_base” ---
**Author:** ![system](https://sea2.discourse-cdn.com/nvidia/user_avatar/forums.developer.nvidia.com/system/32/68080_2.png) [@system](https://forums.developer.nvidia.com/u/system)\ **Post date:** [April 5, 2024, 10:16pm UTC](https://forums.developer.nvidia.com/t/how-do-i-fix-it/280450/10 "2024-04-05T22:16:01Z")
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