How to set collision groups between objects?

[strn18]

Hi,
I would like to configure collision groups between different objects.

My goal is to allow collisions between object A and B, and object B and C, while object A and C should not collide (i.e., A collides with B, and B collides with C, but A and C do not collide. They pass through each other).

I found relevant information in the OmniPhysics documentation, but I’m not sure how to apply this to IsaacLab code.

If you could provide a code snippet or an example showing how to implement this in IsaacLab, I would really appreciate it. Thanks!

[RandomOakForest]

Thank you for posting this. You may try the following:

1. Use different collision_group values per asset (or keep them all 0 and rely on the default behavior) via RigidObjectCfg.collision_group.¹
2. Use InteractiveSceneCfg.filter_collisions and InteractiveScene.filter_collisions(global_prim_paths=...) for environment‑wide filtering, which is officially part of Lab.²

Example of a valid RigidObject config (note: this does not yet encode your A–B–C pattern, just shows a verified config):

from isaaclab.assets import RigidObjectCfg

BOX_A_CFG = RigidObjectCfg(
    prim_path="{ENV_REGEX_NS}/BoxA",
    # spawn=... (your spawn config here)
    collision_group=0,  # or -1 depending on your use case
)

BOX_B_CFG = RigidObjectCfg(
    prim_path="{ENV_REGEX_NS}/BoxB",
    collision_group=0,
)

BOX_C_CFG = RigidObjectCfg(
    prim_path="{ENV_REGEX_NS}/BoxC",
    collision_group=0,
)

Then a scene that filters collisions between environments:

from isaaclab.scene import InteractiveScene, InteractiveSceneCfg
from isaaclab.utils import configclass

@configclass
class MySceneCfg(InteractiveSceneCfg):
    # your terrain / objects / robots, e.g.
    # box_a = BOX_A_CFG
    # box_b = BOX_B_CFG
    # box_c = BOX_C_CFG
    filter_collisions = True  # documented in InteractiveSceneCfg[page:1]

scene_cfg = MySceneCfg(num_envs=128)
scene = InteractiveScene(cfg=scene_cfg)

# Optionally, keep collisions with a global ground prim:
scene.filter_collisions(global_prim_paths=["/World/ground"])  # documented method[page:1]

About implementing the A–B, B–C, not A–C pattern

Right now Isaac Lab does not provide a high‑level collision‑pair API similar to the OmniPhysics “Collision Groups & Filter Pairs” UI, and the Lab documentation does not define a supported Python helper to set per‑pair simulationFilterData on assets. You can technically do it through the underlying USD/PhysX APIs (as in the OmniPhysics docs).

Footnotes

1. https://forums.developer.nvidia.com/t/collision-filter/227404 ↩

2. https://isaac-sim.github.io/IsaacLab/main/source/api/lab/isaaclab.assets.html ↩

[strn18]

Thanks for the reply!
I actually managed to solve the problem by using the USD API. The code I used is as follows:

stage = omni.usd.get_context().get_stage()
collisionGroupPaths = [
    "/World/collisionGroup0",
    "/World/collisionGroup1",
    "/World/collisionGroup2",
]
collisionGroupIncludesRel = [None] * 3
collisionGroupFilteredRels = [None] * 3

for i in range(3):
    collisionGroup = UsdPhysics.CollisionGroup.Define(stage, collisionGroupPaths[i])
    collisionGroupPrim = collisionGroup.GetPrim()
    collectionAPI = Usd.CollectionAPI.Apply(
        collisionGroupPrim,
        UsdPhysics.Tokens.colliders
    )
    collisionGroupIncludesRel[i] = collectionAPI.CreateIncludesRel()
    collisionGroupFilteredRels[i] = collisionGroup.CreateFilteredGroupsRel()

for i in range(self.num_envs):
    collisionGroupIncludesRel[0].AddTarget(f"/World/envs/env_{i}/BoxA")
    collisionGroupIncludesRel[1].AddTarget(f"/World/envs/env_{i}/BoxB")
    collisionGroupIncludesRel[2].AddTarget(f"/World/envs/env_{i}/BoxC")

collisionGroupFilteredRels[0].AddTarget(collisionGroupPaths[2])

With this setup, collisions between BoxA and BoxC are disabled, while collisions between the other pairs remain enabled.
I’m not sure if this is the most optimized implementation, but I confirmed that it works as intended.