HdStorm DomeLight loading performance

[Keli-Li]

Hi,

In HdStorm, seems there are two major factors affecting the performance of loading a domeLight with a large environment map:

1.The output size of pre-processed maps from environment map
https://git.autodesk.com/autodesk-forks/USD/blob/release/pxr/imaging/hdSt/domeLightComputations.cpp#L171

2.The sample count used to sample from environment map
https://git.autodesk.com/autodesk-forks/USD/blob/release/pxr/imaging/hdSt/shaders/domeLight.glslfx#L168

Any idea to expose these two parameters for user adjustment?

Keli

[Keli-Li]

Seems the more important one is the fisrt, Storm use half of source envrionment map as the default downsize. Test shows the loading time can be reduced from 10 sec to 5 sec for an envrionment map (8,234*4,117 pixels, 100M) if the downsize is reduced from half to 1/16.

Meanwhile, seems the generation of Prefilter map from source env map is a multi-runs with compute shader to generate Prefilter map for each mip level.

PixarAnimationStudios/OpenUSD/blob/release/pxr/imaging/hdSt/simpleLightingShader.cpp#L624

Any optimization here, is it possible to run compute shader once for all levels or run compute shader once for level 0 and let GL to generate mipmaps automatically for us?

[Keli-Li]

Hi, I created a request here: Request to expose the downsize to balance between quality and performance for Storm DomeLight · Issue #3342 · PixarAnimationStudios/OpenUSD · GitHub