Camera ISO/exposure affects mesh objects but not 3D Gaussian Splat USD in Isaac Sim

Omniverse Isaac Sim
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GPU Information

  • Model: NVIDIA RTX 4090
  • Driver Version: 580.95.05

Topic Description

Camera ISO / exposure affects regular mesh objects, but does not affect a 3D Gaussian Splatting USD asset in the same Isaac Sim scene.

Detailed Description

I am using Isaac Sim to generate a camera dataset with controlled camera ISO and shutter settings.

The scene contains both regular mesh objects and a 3D Gaussian Splatting USD asset:

  • Regular mesh objects: floor
  • 3D Gaussian Splatting USD exported from a 3DGUT pipeline
  • Robot: custom 3DGS USD
  • Renderer: RayTracedLighting
  • Camera exposure API: OmniRtxCameraExposureAPI_1
  • Camera attributes modified:
    • exposure:iso
    • exposure:time
    • shutter:open
    • shutter:close

I change ISO from 200 to 1600 while keeping the camera pose, scene, shutter time, and lighting fixed.

The regular mesh floor reacts to the ISO change and becomes much brighter. However, the 3D Gaussian Splatting USD background remains almost unchanged.

Screenshots or Videos

Additional Information

What I’ve Tried

  • Verified that exposure:iso is updated on the camera prim.
  • Verified that regular mesh objects react to ISO changes.
  • Captured static frames with the same camera pose, same shutter time, same lighting, and same scene.
  • Compared ISO 200 and ISO 1600 captures.

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Hi @guddk118 ! This is expected behavior. According to the Omniverse RTX Particle Fields documentation:

All ParticleField prims are assumed to have their light fields in display-referred sRGB space. This means that the tonemapping pipeline is skipped for ParticleField prims and they are rendered to the camera “as-is”.

Camera exposure/ISO settings are part of the tonemapping pipeline, so they don’t affect 3DGS assets by design.

Future: RTX will add UsdColorSpaceAPI support for ParticleFields, enabling tonemapping for 3DGS trained in linear color space.

5

Thank you for your reply. I was looking for a way to generate data in a digital twin environment while changing camera parameters, so it is quite unfortunate that 3D Gaussian Splat USD currently does not respond to ISO/exposure changes like regular mesh objects. I will look into other alternatives for now.