Create deformable object

Omniverse Isaac Sim
1

I’m trying to create a deformable object using my URDF/Converted USD file.
The urdf file looks like this:

<?xml version="1.0" encoding="utf-8"?>    
    <robot name="box_0">
        <link name="box_0">    
            <fem>
                <origin rpy="0.0 0.0 0.0" xyz="0 0 0" />
                <density value="100" />
                <youngs value="1005"/>
                <poissons value="0.3"/>
                <damping value="0.0" /> 
                <attachDistance value="0.0"/>
                <tetmesh filename="../../meshes/box_0.tet"/>
                <scale value="1.0"/>
            </fem>
        </link>
    </robot>

I converted this URDF file to USD file using convert_urdf.py script. Then I load this USD file using XFormPrim. By just loading this file to the simulator seems not to work, I can’t see anything inside. Should I assign a material to it? The code I’m using is:

deformable_prim_path = "/World/deformable"
stage.add_reference_to_stage(deformable_usd, deformable_prim_path)

deformable_prim = XFormPrim(
    prim_path=deformable_prim_path,
    position=torch.tensor(np.array([0.0, 0.5, 0.0])).to(device),
    scale=torch.tensor(np.array([0.2, 0.1, 0.02])).to(device),
)
world.scene.add(deformable_prim)

I know there’s a way to create deformable objects (following the same structure given by the Deformable Body in the Physics/Demo Scenes), but I mainly want to use my own urdfs and meshes.

I also notice that there are DeformablePrim, DeformablePrimView, deformableMeshUtils, DeformableMaterial, DeformableMaterialView in the source code but not in the documentation and I don’t know how to utilize these functions to implement my application.

4

the <fem> tag seems to be a custom implementation? can you provide the source where this is defined? The URDF importer only contains standard URDF implementation, and very few custom tags implemented for convenience. While it makes sense, We’d need to verify that the fem tag is properly stablished and have a documented source to point to before we can consider adding support to it.

5

Thanks for getting back to me. I’ll double-check the <fem> tag.

But in general, can you provide me with some guidance on how to create a deformable object using my own mesh/urdf with allowable format?