is it possible to set material on the part of urdf?

[Hankyu-Kim]

I have an urdf file of car which is seperated with chasis and wheel. I can access to each wheels like 'front_left_wheel', 'front_right_wheel', 'rear_left_wheel', and 'rear_right_wheel'. My question is that is it possible to set wheel with some thing like rubber material? I found gs.materials.FEM.Muscle class on genesis and I want to apply it on the wheel so the bottom part of the wheel get flat because of the gravity. Thank you

Urdf source

https://github.com/osrf/car_demo/blob/master/prius_description/urdf/prius.urdf

Code

import numpy as np
import genesis as gs

gs.init(backend=gs.gpu)

scene = gs.Scene(
    viewer_options=gs.options.ViewerOptions(
        camera_pos=(10, 5, 2),
        camera_lookat=(0.0, 0.0, 0.5),
        camera_fov=60,
        res=(960, 640),
        max_FPS=30,
    ),
    sim_options=gs.options.SimOptions(dt=0.01),
    show_viewer=True,
)

scene.add_entity(gs.morphs.Plane())
prius = scene.add_entity(
    morph=gs.morphs.URDF(
        file="urdf/prius_description/urdf/prius.urdf",
        # pos=(0.5, 0.5, 0.3),
        # euler=(0.0, 0.0, 0.0),
        # scale=0.2,
        # fixed=True,
    ),
    # material=gs.materials.Hybrid(
    #     mat_rigid=gs.materials.Rigid(
    #         gravity_compensation=1.,
    #     ),
    #     mat_soft=gs.materials.MPM.Muscle( # to allow setting group
    #         E=1e4,
    #         nu=0.45,
    #         rho=1000.,
    #         model='neohooken',
    #     ),
    #     thickness=0.05,
    #     damping=1000.,
    #     func_instantiate_rigid_from_soft=None,
    #     func_instantiate_soft_from_rigid=None,
    #     func_instantiate_rigid_soft_association=None,
    # ),
)

scene.build()

steering_joints = [
    'steering_joint',
    'front_left_steer_joint',
    'front_right_steer_joint',
]

wheels_joints = [
    'front_left_wheel_joint',
    'front_right_wheel_joint'
]

steering_dofs_idx = [prius.get_joint(name).dof_idx_local for name in steering_joints]
wheel_dofs_idx = [prius.get_joint(name).dof_idx_local for name in wheels_joints]

prius.set_dofs_position(np.array([0.5, 0.5, 0.5]), steering_dofs_idx)

prius.set_dofs_kp(kp=np.array([0, 0]), dofs_idx_local=wheel_dofs_idx)  # Zero positional gains for pure velocity control
prius.set_dofs_kv(kv=np.array([50, 50]), dofs_idx_local=wheel_dofs_idx)  # Damping for smooth velocity control

velocity_command = np.array([30.0, 30.0])  # Adjust speed (rad/s)

for _ in range(1500):
    prius.control_dofs_velocity(velocity_command, wheel_dofs_idx)

    current_velocity = prius.get_dofs_velocity(wheel_dofs_idx)
    print(f"Wheel Velocities: {current_velocity}")

    scene.step()

Play video

simplescreenrecorder-2025-02-10_22.18.44.mp4