[Question] lidar can't detect obstacles

[Bruce-Si]

Question

I am trying to load a scene from USD file instead of generating it by terrain_generator. The USD file is exported from blender. Since only a single static mesh is supported for the RayCaster in Isaac, I merged all the meshes to a single one. I also added the Collider property for the mesh in Isaac Sim for physical simulation. Finally, the scene looks like:

I modified the TerrainImporterCfg to:

        terrain_cfg = TerrainImporterCfg(
            num_envs=self.num_envs,
            env_spacing=0.0,
            prim_path="/World/ground",
            usd_path="scene.usdc",
            terrain_type="usd",
            collision_group=-1,
            debug_vis=True,
        )

But the simulation results show that the lidar can't detect obstacles correctly in the new scene. It can detect the ground, but can't detect the terrain. Sometimes it seems to detect the air...

For example, the following two imgs show the correct detect result in the preview generated scene, and the wrong result in the loaded scene:

I am using Isaac Sim 2023.1.0-hotfix.1and Orbit. Is my problem due to the old version or other issues...

Any help, tks!!!

[RandomOakForest]

Thank you for posting this. Please update to the latest Isaac Sim, as this may resolve the issues. If it doesn't we'd be able to repro and be in the same page to address your problem. Thank you.

[Bruce-Si]

Thank you for posting this. Please update to the latest Isaac Sim, as this may resolve the issues. If it doesn't we'd be able to repro and be in the same page to address your problem. Thank you.

Thank you. I found that the bug was caused by not performing “mesh triangulation.” After triangulating, the problem was resolved. However, there’s still another issue — is there currently any method to export a level from Unreal Engine to Isaac? Directly exporting as USD causes material and texture bugs.

[Fuhua-Bot]

Thank you for posting this. Please update to the latest Isaac Sim, as this may resolve the issues. If it doesn't we'd be able to repro and be in the same page to address your problem. Thank you.

Thank you. I found that the bug was caused by not performing “mesh triangulation.” After triangulating, the problem was resolved. However, there’s still another issue — is there currently any method to export a level from Unreal Engine to Isaac? Directly exporting as USD causes material and texture bugs.

Hi, Bruce, I met the same issue several month ago, good to hear you have made it. could you please explain it more clearly? thanks.

[Bruce-Si]

Thank you for posting this. Please update to the latest Isaac Sim, as this may resolve the issues. If it doesn't we'd be able to repro and be in the same page to address your problem. Thank you.

Thank you. I found that the bug was caused by not performing “mesh triangulation.” After triangulating, the problem was resolved. However, there’s still another issue — is there currently any method to export a level from Unreal Engine to Isaac? Directly exporting as USD causes material and texture bugs.

Hi, Bruce, I met the same issue several month ago, good to hear you have made it. could you please explain it more clearly? thanks.

Of course.My goal is to export a level from Unreal Engine to Isaac Sim.

Directly importing the UE-exported USD into Isaac results in incorrect materials and mesh placements. Using Blender as a middleman helps fix some material issues and simple scene misalignments.

The main problem I faced next was with the raycaster in Isaac, which gave bad collision results. I found that all meshes need to be triangulated for Isaac. After triangulating everything in Blender, the raycaster issue was solved.

However, fully solving the material/texture mapping and complex scene mesh placement issues remains an ongoing challenge.

Hope that clarifies things.

[Fuhua-Bot]

Thank you for posting this. Please update to the latest Isaac Sim, as this may resolve the issues. If it doesn't we'd be able to repro and be in the same page to address your problem. Thank you.

Thank you. I found that the bug was caused by not performing “mesh triangulation.” After triangulating, the problem was resolved. However, there’s still another issue — is there currently any method to export a level from Unreal Engine to Isaac? Directly exporting as USD causes material and texture bugs.

Hi, Bruce, I met the same issue several month ago, good to hear you have made it. could you please explain it more clearly? thanks.

Of course.My goal is to export a level from Unreal Engine to Isaac Sim.

Directly importing the UE-exported USD into Isaac results in incorrect materials and mesh placements. Using Blender as a middleman helps fix some material issues and simple scene misalignments.

The main problem I faced next was with the raycaster in Isaac, which gave bad collision results. I found that all meshes need to be triangulated for Isaac. After triangulating everything in Blender, the raycaster issue was solved.

However, fully solving the material/texture mapping and complex scene mesh placement issues remains an ongoing challenge.

Hope that clarifies things.

Very helpful, thanks a lot, I am not an expert of blender, so I use CAD software like fusion360 to create the usd, now its the time to learn it. Thanks!