Scattering 20,000 grass instances (without collision check) is not possible

Omniverse Isaac Sim
1

Isaac Sim Version

4.0.0

Operating System

Windows 11

GPU Information

  • Model: RTX 4090 Laptop
  • Driver Version: 566.36

Steps to Reproduce

  1. scatter 20,000 instances of a small mesh using a scatter node

Screenshots or Videos

image
image498×310 101 KB

Topic Description

When i start my simulation, I scatter small patches of grass. Until now, I scattered 2000 instances.
If I increase the number of instances to 20000, the editor frizes.

this is how I initialize my scatter graph:

def init_graph(self, surface_prims_path, rand_usd_paths):
        self.graph = og.Controller.create_graph(
            graph_id = {
                "graph_path" : f"/Graphs/ScatterGraphs/grass_Graph",
                "fc_backing_type" : og.GraphBackingType.GRAPH_BACKING_TYPE_FABRIC_WITHOUT_HISTORY, 
                "pipeline_stage" : og.GraphPipelineStage.GRAPH_PIPELINE_STAGE_ONDEMAND
            }
            )

        keys = og.Controller.Keys
        _, _, _, nodes = og.Controller.edit(
            self.graph,
            {
                keys.CREATE_NODES: [
                    ("OgnScatter2D", "omni.replicator.core.OgnScatter2D"),
                    ("OgnSamplePopulation", "omni.replicator.core.OgnSamplePopulation"),
                    ("OgnCount1", "omni.replicator.core.OgnCount"),
                    ("OgnCount2", "omni.replicator.core.OgnCount"),
                    ("OgnSampleUniform", "omni.replicator.core.OgnSampleUniform"),
                    ("PerAxisPose", "omni.replicator.core.OgnPerAxisPose"),
                    ("OgnWritePrimAttribute", "omni.replicator.core.OgnWritePrimAttribute"),
                    ],
                keys.CONNECT: [
                    ("OgnSamplePopulation.outputs:prims", "OgnCount1.inputs:prims"),
                    ("OgnCount1.outputs:count", "OgnSampleUniform.inputs:numSamples"),
                    ("OgnSampleUniform.outputs:samples", "PerAxisPose.inputs:fullValues"),

                    ("OgnSamplePopulation.outputs:prims", "OgnCount2.inputs:prims"),
                    ("OgnCount2.outputs:count", "PerAxisPose.inputs:numSamples"),

                    ("OgnSamplePopulation.outputs:prims", "PerAxisPose.inputs:prims"),

                    ("PerAxisPose.outputs:samples", "OgnWritePrimAttribute.inputs:values"),
                    ("OgnSamplePopulation.outputs:prims", "OgnWritePrimAttribute.inputs:prims"),

                    ("OgnSamplePopulation.outputs:exec", "OgnScatter2D.inputs:execIn"),
                    ("OgnSamplePopulation.outputs:exec", "PerAxisPose.inputs:exec"),
                    ("PerAxisPose.outputs:exec", "OgnWritePrimAttribute.inputs:execIn"),

                    ("OgnSamplePopulation.outputs:prims", "OgnScatter2D.inputs:prims"),


                ],
                keys.SET_VALUES: [
                 
                    ("OgnSamplePopulation.inputs:paths", rand_usd_paths),
                    ("OgnSamplePopulation.inputs:mode", 'scene_instance'),
                    ("OgnSamplePopulation.inputs:useCache", False),
                    ("OgnSamplePopulation.inputs:withReplacements", False),
                    ("OgnSamplePopulation.inputs:populationName", f"{self.assets_name}_ScatterPopulation"),

                    ("OgnCount1.inputs:mode", 'prims'),

                    ("OgnSampleUniform.inputs:lower", [0,0,0]),
                    ("OgnSampleUniform.inputs:upper", [0,0,180]),
                    ("OgnSampleUniform.inputs:outputType", "float3[]"),

                    ("OgnCount2.inputs:mode", 'prims'),

                    ("PerAxisPose.inputs:mode", "rotation"),

                    ("OgnWritePrimAttribute.inputs:attribute", "xformOp:rotateXYZ"),
                    ("OgnWritePrimAttribute.inputs:attributeType", "double3"),

                    #("OgnScatter2D.inputs:surfacePrims", plane_path),   
                    ("OgnScatter2D.inputs:checkForCollisions", False),
                    ("OgnScatter2D.inputs:seed", self.seed),
                ]
            },
        )

what am i doing wrong? how is it possible to scatter many meshes in Isaac Sim?

2

Could you test version 4.2.0? If the issue persists, do you notice any suspicious messages? Please share the complete code for easier reproduction.

3

@VickNV Thank you for your responce.

here is a simple test case:

  1. create an empty stage with a plane mesh.

  2. download the attacked usd file (this is a patch of grass)
    Collected_Bunch of Grass1.zip (2.7 MB)

  3. past this code in the script editor:

import omni.replicator.core as rep

grass_usd = "<path to where the downloaded grass usd is>"

plane_path = "/World/Plane"

plane_prim = rep.get.prim_at_path(plane_path)

grass = rep.randomizer.instantiate(paths = grass_usd, size = 10000, use_cache = False)

rep.randomizer.scatter_2d(input_prims = grass, surface_prims = plane_prim)
  1. press “Run”

For this simple test case, it has been running for the last 20 minutes and the editor is still stuck (waiting for the scattering to complete).

BTW, I see that my system is not being fully utilized:

image
image261×524 11.1 KB

image
image309×198 19.8 KB

any idea on how I can better utilize my CPU and/or GPU to lower the time it takes to scatter?

Thank you