Autodesk: Generate optimal MaterialX shaders via lobe pruning #3525
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Introduces the lobe pruning concept to MaterialX shaders generated by
Storm
We look into shader graph implemnetation and find where we can cut the graph to simplify it based on the value of the main lobe attributes.
This means a shader with a subsurface weight of zero will completely prune the evaluation of the subsurface, while a value of 1 will completely prune the evaluation of the dielectric base.
This provides interesting performance values:
```
Playback of a rotating 11x11x11 cube of cubes in usdView:
Before:
light: Dome Default
UsdPreviewSurface 29fps 23fps
mx::StandardSurface 15fps 20fps
mx::OpenPBRSurface 7fps 12fps
After:
light: Dome Default
mx::StandardSurface 29fps 22fps
mx::OpenPBRSurface 29fps 22fps
```
Looks refresh-limited, better test rig required.
Technical side: The code looks for nodes in the nodegraph implementation and checks any node that directly connects to the interface on a 0-1 slider:
- Mix nodes: If the mix value if 0 or 1, forward the value/connection of the bg or fg port to the node directly upstream. Delete node.
- Multiply nodes: If any value is zero, write zero to the corresponding port on the upstream node. Delete node.
- PBR nodes: If the weight parameter is zero, substitute with a no-op PBR node. Delete node.
This makes sure the ShaderGen works on a reduced codebase and greatly reduces code size and complexity by disconnecting unused subgraphs and skipping black PBR calls.
erikaharrison-adsk
changed the title
Will also fix other case sensitive OS.
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Filed as internal issue #USD-10661 (This is an automated message. See here for more information.) |
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Description of Change(s)
Introduces the lobe pruning concept to MaterialX shaders generated by Storm
We look into shader graph implemnetation and find where we can cut the graph to simplify it based on the value of the main lobe attributes.
This means a shader with a subsurface weight of zero will completely prune the evaluation of the subsurface, while a value of 1 will completely prune the evaluation of the dielectric base.
This provides interesting performance values:
Looks refresh-limited, better test rig required.
Technical side: The code looks for nodes in the nodegraph implementation and checks any node that directly connects to the interface on a 0-1 slider:
This makes sure the ShaderGen works on a reduced codebase and greatly reduces code size and complexity by disconnecting unused subgraphs and skipping black PBR calls.
Link to proposal (if applicable)
Fixes Issue(s)
Checklist
I have created this PR based on the dev branch
I have followed the coding conventions
I have added unit tests that exercise this functionality (Reference:
testing guidelines)
I have verified that all unit tests pass with the proposed changes
I have submitted a signed Contributor License Agreement (Reference:
Contributor License Agreement instructions)