MPMized an URDF rigid entity

[cjt0313]

Hi there, i tried to load an urdf file with MPM material setups, the error suggest an URDF morph cannot be coupled with materials.MPM. Here are my questions:

1. Is there any solution to this?
2. how can i set the meterial parameters in a particle-wise level?
3. how can i use the gradient w.r.t. C&F in MPMEntity._solver.particles.grad, i've notived the material is settled in scene initialization, is there any way to set the material during scene steps? (just like set_postion, set_velocity etc.)

Plus: i come up with an idea of load the urdf first, and dump the mesh into .obj files, then reload the mesh file as a deformable object, but i didn't find a supported function yet.