Turn off collisions for invisible objects in replicator

Omniverse Synthetic Data Generation (SDG)
1

Hi!
I’m trying to simulate different layouts of cases on a pallet and I’m using the replicator to toggle the visibility of cases. The cases I use have to have a collision for other parts of the simulation I’m doing, but I’d like to turn the collision off when the case is invisible. This is the code I’m currently working with:

  def case_visibility_randomizer(self):
      omni.log.info(f"Randomize case visibility")
      case_pattern = r"/World/Pallets/Pallet_0/Layer_\d+/Case_\d+/"

      cases = rep.get.prims(path_pattern=case_pattern, prim_types="Mesh")
      with cases:
          rep.modify.visibility(rep.distribution.sequence([True, False]))
          rep.modify.attribute("physics:collisionEnabled", rep.distribution.sequence([True, False]))
      return cases.node

If I try to change the attribute as shown in the code I get the following error:

2025-03-18 13:48:33 [47,272ms] [Error] [omni.graph.core.plugin] /Replicator/SDGPipeline/WritePrimAttribute_physics_collisionEnabled: [/Replicator/SDGPipeline] OmniGraph Error: WritePrimAttribute Error: cannot reshape array of size 1 into shape (60,newaxis)
                 (from compute() at line 236 in /home/developer/.local/share/ov/pkg/isaac-sim-4.2.0/extscache/omni.replicator.core-1.11.20+106.1.0.lx64.r.cp310/omni/replicator/core/ogn/python/_impl/nodes/OgnWritePrimAttribute.py)
[35.910s] [Level.ERROR] [None] [Node.cpp:1860] : /Replicator/SDGPipeline/WritePrimAttribute_physics_collisionEnabled: [/Replicator/SDGPipeline] OmniGraph Error: WritePrimAttribute Error: cannot reshape array of size 1 into shape (60,newaxis)
                 (from compute() at line 236 in /home/developer/.local/share/ov/pkg/isaac-sim-4.2.0/extscache/omni.replicator.core-1.11.20+106.1.0.lx64.r.cp310/omni/replicator/core/ogn/python/_impl/nodes/OgnWritePrimAttribute.py)

Is there any way to turn the collider off, ideally directly linked to the visibility parameter of each case?
Thank you in advance for any input!

2

Hi there,

there seems to be an issue with rep.modify.attribute that it searches for the attribute on the child prim. I submitted a bug report for this.

As a workaround you could either use the functionality by making sure you apply it to the prim which has the attribute or you could
use a more flexible approach with replicator separating randomization, simulation, and data capturing.

  • you can do this by using rep.orchestrator.step() whenever you want to capture a frame
  • if you want to use the replicator built in randomization, you can use rep.trigger.on_custom_event() to trigger randomization, to avoid triggering when calling the rep.orchestrator.step() function
  • this allows you to also have USD or Isaac Sim API randomizations in the same pipeline, here you can for example use a workaround for replicator collision issue.

Here are some examples of such workflows:

3

Thank you for your answer, I will take a look at it!