Custom simulation and deformation meshes for deformable objects?

Omniverse Isaac Sim
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Isaac Sim Version

4.5.0

Topic Description

I want to experiment with creating my own tetrahedral meshes for use in deformable object in Isaac Sim. When I create a deformable object in Isaac Sim, i can see that the PhysxDeformableBodyAPI and PhysxCollisionAPI are applied to the prim. I also see that the generated collision an deformation tet meshes are stored in properties, for example physxDeformable:collisionPoints. But I realize these buffers are dynamic, eg if I set PhysxDeformable:simulationHexahedralResolution the simulation mesh will be regenerated.

When I look at the output USD of a simple deformable object created in Isaac Sim, I see some custom properties eg collisionSimplificationRemeshing that are not part of the PhysxDeformableBodyAPI schema that when changed will potentially force Isaac Sim to rebuild the tet meshes. If i just remove these custom properties and load a USD scene Isaac does not just use the predefined tet mesh buffer properties.

How can I setup an object so Isaac Sim will just use the collision and deformation tet meshes defined in the object properties and not try to recalculate them?

I have also read about the Omni Physics Deformable Schema where you can define other prims as the collision and deformation meshes, is this a viable option? But it also talked about some of the implementation limitations which limit 1: of the visual and sim meshes so may not be useful.

Any help is appreciated,

G

3

Hi @geordie_GR, thank you for posting your question.

You can disable physxDeformable:collisionSimplification so that it uses the original mesh. Simplification runs dynamically so it will even remesh as you change the resolution during simulation.

To clarify, do you mean using the deformable for visualization but attaching a rigid body as a collider?

4

Thanks for your reply! I read more about Omni Physics Deformable Schema and realize it’s on available in Isaac 5 (which we’ll hopefully upgrade to soon).

I was hoping I could fashion my own custom tetrahedral meshes with varying stiffness throughout the deformable model, so was hoping there’d be a “disable dynamic simplification” option somewhere and just use another prim or primvars for the tet meshes. But looking into the physx deformable data I’m not sure it supports stiffness variance anyway.