A Problem of Friction Disappearing Between GO2 and Ground

[kentliukx]

After reading the tutorials, I tried to implement a GO2 in Genesis. However, friction didn't seem to work correctly. Can Anyone kindly tell me what I missed while initializing the ground or GO2? Thanks a lot!

Environment
Ubuntu 24.04.2 LTS
Python 3.10.18
taichi 1.7.4
GPU: NVIDIA GeForce RTX 4070m
Driver Version: 575.64.03
CUDA Version: 12.9
Release version or Commit ID

commit hash: 4a2987e

Following is my code:

import numpy as np

import genesis as gs

########################## init ##########################
gs.init(backend=gs.gpu)

########################## create a scene ##########################
scene = gs.Scene(
    viewer_options=gs.options.ViewerOptions(
        camera_pos=(0, -3.5, 2.5),
        camera_lookat=(0.0, 0.0, 0.5),
        camera_fov=30,
        max_FPS=60,
    ),
    sim_options=gs.options.SimOptions(
        dt=0.01,
    ),
    show_viewer=True,
)

########################## entities ##########################
plane = scene.add_entity(
    gs.morphs.URDF(
        file="urdf/plane/plane.urdf",
        fixed=True,
    ),
    material=gs.materials.Rigid(friction=1.0),
)

go2 = scene.add_entity(
    gs.morphs.URDF(
        file="urdf/go2/urdf/go2.urdf",
        pos=[0.0, 0.0, 0.58],
        quat=[0, -0.707, 0.0, 0.707],
    ),
    material=gs.materials.Rigid(friction=1.0),
)
########################## build ##########################
scene.build()

joints_name = (
    "FR_hip_joint",
    "FR_thigh_joint",
    "FR_calf_joint",
    "FL_hip_joint",
    "FL_thigh_joint",
    "FL_calf_joint",
    "RR_hip_joint",
    "RR_thigh_joint",
    "RR_calf_joint",
    "RL_hip_joint",
    "RL_thigh_joint",
    "RL_calf_joint",
)
motors_dof_idx = [go2.get_joint(name).dofs_idx_local[0] for name in joints_name]

for i in range(10000):
    go2.set_dofs_position(np.array([-0.1, 1, -2, 0.1, 1, -2, -0.1, 2.2, -1.2, -0.1, 2.2, -1.2]), motors_dof_idx)
    scene.step()
    print("joint angles:", go2.get_dofs_position(motors_dof_idx)),
    print("pos:", go2.get_pos())

[kentliukx]

Go2 should be rotating with its feet static as soon as it touches the ground vertically, but there seems to be no friction between its feet and the ground.
录屏 2025-08-18 00-55-35.webm

[kentliukx]

When I use control_dofs_position friction seems to be working correctly. So set_dofs_position causes physics to behave weird within its step, I see that.

[duburcqa]

Yes, exactly. By definition set_dofs_position will completely mess up with the physics to forcibly overwriting it, then control_dofs_position will just update the low-pid target positions, which in turns will compute physically plausible joint torques proportional to the tracking error.