Error occurs when trying to set rigid bodies in environment in Isaac Sim GUI

[brandon-lawrence96]

Hi my name is Brandon. Currently, I am trying to make some objects in the office environment into rigid bodies in the Isaac Sim GUI but when I do so, I keep getting this error in my terminal before Isaac Sim crashes. The error is:

Traceback (most recent call last):
File "/home/ubuntu/go2_omniverse/main.py", line 29, in
run_sim()
File "/home/ubuntu/go2_omniverse/omniverse_sim.py", line 607, in run_sim
obs, _, terminated, _ = env.step(actions_reordered)
File "/home/ubuntu/IsaacLab-0.3.1/source/extensions/omni.isaac.orbit_tasks/omni/isaac/orbit_tasks/utils/wrappers/rsl_rl/vecenv_wrapper.py", line 160, in step
obs_dict, rew, terminated, truncated, extras = self.env.step(actions)
File "/home/ubuntu/IsaacLab-0.3.1/_isaac_sim/kit/python/lib/python3.10/site-packages/gymnasium/wrappers/order_enforcing.py", line 56, in step
return self.env.step(action)
File "/home/ubuntu/IsaacLab-0.3.1/source/extensions/omni.isaac.orbit/omni/isaac/orbit/envs/rl_task_env.py", line 177, in step
self.scene.update(dt=self.physics_dt)
File "/home/ubuntu/IsaacLab-0.3.1/source/extensions/omni.isaac.orbit/omni/isaac/orbit/scene/interactive_scene.py", line 276, in update
sensor.update(dt, force_recompute=not self.cfg.lazy_sensor_update)
File "/home/ubuntu/IsaacLab-0.3.1/source/extensions/omni.isaac.orbit/omni/isaac/orbit/sensors/sensor_base.py", line 195, in update
self._update_outdated_buffers()
File "/home/ubuntu/IsaacLab-0.3.1/source/extensions/omni.isaac.orbit/omni/isaac/orbit/sensors/sensor_base.py", line 279, in _update_outdated_buffers
self._update_buffers_impl(outdated_env_ids)
File "/home/ubuntu/IsaacLab-0.3.1/source/extensions/omni.isaac.orbit/omni/isaac/orbit/sensors/contact_sensor/contact_sensor.py", line 309, in _update_buffers_impl
net_forces_w = self.contact_physx_view.get_net_contact_forces(dt=self._sim_physics_dt)
File "/home/ubuntu/.local/share/ov/pkg/isaac-sim-2023.1.1/extsPhysics/omni.physics.tensors-105.1.12-5.1/omni/physics/tensors/impl/api.py", line 1416, in get_net_contact_forces
raise Exception("Failed to get net contact forces from backend")
Exception: Failed to get net contact forces from backend

If anyone is able to assist on this, I would be very grateful. Thank you.

[abizovnuralem]

Hello, you can search in issues , we have solved this issue with some settings in Isaac .

[abizovnuralem]

#33 Here

[brandon-lawrence96]

Hi @abizovnuralem. Thank you for your reply. However, upon reading #33, it only addresses the issue of adding collider presets to objects in the simulation and it does not address the issue of adding rigid body with collider presets which is when my error occurs. Thank you.

[abizovnuralem]

Can I ask you the reason why you want to add rigid bodies ?

[brandon-lawrence96]

I want the go2 robot's base to detect a contact(collision) when it hits an object of interest to me but I realise that when I print out the contact sensor readings for the base, it is always [0 0 0] even when a collision with the wall occurs. Only the contact sensor readings for the feet seem to be correct. I am wondering if it is because I did not set the object to be rigid body in the simulation?

[abizovnuralem]

Be default, I set the project to ignore all physical objects inside environment , so if you go with #33 the dog will have collisions with objects and cannot go inside the other physical objects , for the sensor output I suggest to read some examples in train.py and go through reward functions (that have collisions reward ) and see the difference in code . Maybe this info will be helpful for your

[brandon-lawrence96]

What do you mean by train.py? Also, essentially what I want to achieve is to terminate and restart the episode when a collision occurs. Do you know how I can achieve this as it does not seem to be happening currently when a collision between the robot base and an object occurs.

[abizovnuralem]

https://github.com/isaac-sim/IsaacLab/blob/a29bea03bcc3e3365d47753d256ee9a4a14eb9eb/source/standalone/workflows/rsl_rl/train.py#L4 You can view the full logic of collision/restart and reward functions from this entry file , hope it will help you better understand the logic

[brandon-lawrence96]

Thank you for the link. Could I also check with you on one more thing. Why is it that there seems to be contact (collision) being detected between the calf and the thigh of the robot's legs even though I believe self-collisions have been disabled. You can refer to my video which shows the contact represented by a red spherical marker.
Screencast from 01-06-2025 04:47:12 PM.webm

[abizovnuralem]

Thank you for the link. Could I also check with you on one more thing. Why is it that there seems to be contact (collision) being detected between the calf and the thigh of the robot's legs even though I believe self-collisions have been disabled. You can refer to my video which shows the contact represented by a red spherical marker. Screencast from 01-06-2025 04:47:12 PM.webm

I cannot tell why, but I know that when I train the custom NN, I do not include legs as part of collision bodies. Maybe this is a reason why you see collisions between body parts