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[hdEmbree] add support for lighting double-sided meshes (hdEmbree-UsdLux-PR08) #3195

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@pmolodo pmolodo commented Jul 31, 2024

Description of Change(s)

  • ie, we respect the doubleSided attribute on meshes

Related PRs:

This PR is part of a chain of PRs that provide a reference implementation of UsdLux as part of hdEmbree.

◀️ Previous PR in chain: 🔽 This PR changes only: ▶️ Next PR in chain:
#3196 Diff vs Previous

Due to a github limitation, this PR must include all previous PRs in the chain. To see JUST the changes in this PR vs the previous in the chain, click this link

#3197

⛓️ All PRs in this chain:

📃 Documentation PR:
This chain of PRs (implementing UsdLux support in hdEmbree), was made separate from the PR documenting expected UsdLux behavior:

✳️ All UsdLux update related PRs:
To see ALL UsdLux update related PRs (documentation AND reference implementation) in one place, see:

Original PR:
These PRs are an update of this original PR:


But... why??

Why make these PRs in the first place?

The current specifications of the various UsdLux prims + attributes are imprecise or vague in many places, and as a result, actual implementations of them by various renderers have diverged, sometimes quite significantly. For instance, here is Intel's 4004 Moore Lane scene, with the same UsdLux lights defined, in 3 different renderers:

Karma:
4004 Moore Lane, rendered in Karma

Arnold:
4004 Moore Lane, rendered in Arnold

Omniverse RTX:
4004 Moore Lane, rendered in Omniverse RTX

For a full descpription of the problem, see here:

Why so many PRs?
This was my attempt to break up a rather large change into smaller, more easily reviewable changes, that can be merged in incrementally, to help ease the burden for code reviewers.

If you find this confusing, and would rather just one big PR (ie, just this one), or have them organized in some other way, please let me know!

Why are the documentation changes in their own PR?
In some ways, the documentation changes are the heart of this effort - we wish to specify more exactly what the various UsdLux prims and attributes represent. However, building consensus on this may take time - so we expect some dialogue on the exact language or formulas.

Because that may take time, the hdEmbree reference implementation changes are separate, and broken up, so we can hopefully start integrating portions of them even before final consensus has been reached on the final form of the specification.

Why are the documentation changes not broken up into smaller pieces, like the hdEmbree reference implementation changes?
Because I wasn't sure if that would be desirable or not! If people think that would be helpful, I can do so - perhaps breaking out by schema or individual attribute?


  • I have verified that all unit tests pass with the proposed changes
  • I have submitted a signed Contributor License Agreement

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Filed as internal issue #USD-9913

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/AzurePipelines run

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Azure Pipelines successfully started running 1 pipeline(s).

@pmolodo pmolodo changed the title [hdEmbree] add support for lighting double-sided meshes [hdEmbree] add support for lighting double-sided meshes (hdEmbree-UsdLux-PR13) Aug 7, 2024
@pmolodo pmolodo force-pushed the pr/hdEmbree-double-sided-mesh branch from 23622c5 to d510234 Compare September 23, 2024 18:11
@pmolodo pmolodo force-pushed the pr/hdEmbree-double-sided-mesh branch from d510234 to ddbc337 Compare October 21, 2024 17:06
@pmolodo pmolodo changed the title [hdEmbree] add support for lighting double-sided meshes (hdEmbree-UsdLux-PR13) [hdEmbree] add support for lighting double-sided meshes (hdEmbree-UsdLux-PR08) Oct 21, 2024
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/AzurePipelines run

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Azure Pipelines successfully started running 1 pipeline(s).

@pmolodo pmolodo force-pushed the pr/hdEmbree-double-sided-mesh branch 2 times, most recently from 65f44f3 to 2559f99 Compare October 23, 2024 17:29
pmolodo and others added 4 commits October 23, 2024 11:16
This modifies the hdEmbree example plugin to do direct lighting so as to
provide a reference implementation of the expected behaviour for UsdLux.

If no lights are present in the stage, the old ambient occlusion path
will be used.
@pmolodo pmolodo force-pushed the pr/hdEmbree-double-sided-mesh branch from 2559f99 to 035a0d1 Compare October 23, 2024 18:20
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