Point cloud support

[lilleyse]

pnts support was recently added to Cesium Native: CesiumGS/cesium-native#591. At some point we should investigate rendering point clouds in Omniverse.

• What is or isn't possible with USD?
• How do we maintain constant pixel size? See @kring's comment in Point cloud shading cesium-unity#201 (comment). I don't think we can write our own vertex shaders, but Fabric allows you to update GPU vertex data directly: http://omniverse-docs.s3-website-us-east-1.amazonaws.com/usdrt/5.0.0/docs/whatsinfabric.html#deforming-a-mesh-on-the-gpu-with-warp
• How much control do we have over point cloud shading, e.g. would it be possible to implement eye dome lighting? CC Point cloud shading cesium-unity#201

[lilleyse]

Also see point cloud rendering with Omniverse Flow: https://docs.omniverse.nvidia.com/app_create/prod_extensions/ext_pointclouds.html

[corybarr]

After talking with @lilleyse, we decided to save points and render directly in Fabric and bypass using USD/Flow. Aside from the performance boost of going straight to Fabric, there are a few other potential benefits:

• Control over the type of created geometry (quads initially, but potentially cubes)
• control over attenuation
• potentially using pre-baked metadata, like distances to neighbors help scale point representations

[lilleyse]

@corybarr could you open issues for the remaining point clouds tasks and add them as a checklist here? I think it looks something like this, but please add any others that are missing.

• CUDA kernel to generate quads / voxels to avoid slowdown in FabricGeometry
• CUDA kernel for billboarding
• Geometric-error based attenuation, similar to what Cesium for Unity or CesiumJS are doing
• Material support, i.e. ability to show/hide or set color for points in an MDL. Includes making per-point properties like intensity and classification available as primvars.
• Eye dome lighting or some other surface shading technique, depending on what we can do in Omniverse

[corybarr]

@lilleyse Sure:

• Add geometric-error based attenuation to point clouds #430
• Add CUDA support with kernel to generate quads / voxels to avoid slowdown in FabricGeometry #431
• Add initial point-cloud UI with controls for base size, max attenuation, etc. #432
• Add CUDA kernel for point-cloud quad billboarding #433
• Allow users to supply a sprite for point-cloud quad display #434
• Add material support for point clouds #435
• Add Eye-Dome Lighting or some other surface shading technique to point clouds #436

[lilleyse]

Initial point cloud rendering support was added in #424