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There is no support for exporting Shader networks to MaterialX.
MaterialX as UsdShade
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(transport, composition, file format plugin, interop, shader definition)
The import workflow of MaterialX to UsdShade is done by the UsdMtlx plugin. The UsdMtlx plugin translates MaterialX data to UsdShade.
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For HdStorm, a MaterialX document is reconstructed from UsdShade Network to create glslfx via CodeGen. The missing features in the UsdMtlx plugin makes HdStorm hard to use and extend for other Viewport work-flows.
MaterialX in Hydra
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(visualization, viewport, runtime, rendering)
To leverage MaterialX CodeGen (or ShaderGen) functionality in Hydra a delegate is required to reconstruct a MaterialX document from UsdShade or natively handle UsdShade graphs.
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- For multi-backend support for Vulkan, MDL, Metal, etc applications need to maintain multiple Shader Gen paths that can easily get out of sync and are hard to maintain.
- MaterialX nodes as ground truth definitions of UsdPreviewSurface.
- UsdLux v.s MaterialX Light nodes
- Customize shaders for selection, highlighting.
- For Hardware renderers customize shader stages, render state management
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Areas for
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Review
| Expand |
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| Property | Description | USD level | USD/MTLX level | MTLX level | Status | Proposal(s) |
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| namespace | Helpful to qualify definitions with a given scope to avoid name clashes.
e.g. there may be a Adobe vs ILM namespace. |
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| Issue 1614 logged | - Encode namespace as part of definition identifier (no consensus) (PR 1631)
| | colorspace | Color management tagging for inputs as well as color management system specification. | Y |
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| - Agreement to support as formal property. Needs scoping and definition.
- Issue 1532 logged for MTLX export. Internal issue: USD-6703 (old - pre-agreement)
| - "Follow what is going on with MaterialX". (vague)
| | ui value properties | Hints for UI. e.g. ui min, max, step etc. | Y |
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| Separate proposal for this. |
| | unit / dimension support | Support for a real world unit or dimension for an given shader input. The type of the unit may be dynamic / data driven. |
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| Issue 1632 logged. Internal issue: USD-6928. |
| | tokens | Import and resolving of token names used for geometric and file identifiers. Can include consistency of token delimiters |
| Y |
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| | fileprefx |
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| Issue 974 logged. Admin: not closed | | | version | Definition versioning |
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| tbd |
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| Expand |
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| Support multiple |
| Expand |
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| Property | Description | USD level | USD/MTLX level | MTLX level | Status | Proposal(s) |
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| Support nodes with multiple outputs |
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| issue 1581 logged. Internal issue: USD-6820 |
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| | definition information association | Import does not capture the correct association between a definition and a nodegraph sometimes. |
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| Issue 1629 logged | - Specific code fix proposed for conversion to MaterialX
| | definition variations | Definitions may be specified in a variety of different ways. Not all appear to be consumable properly. Some deal with definition discovery. |
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| issue 1636 logged | - Refactor import discovery logic. (PR 1641)
| | definition search path | Related to definition discovery (definition not found in path) |
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| Issue 1586 logged. Internal issue USD-6941 | - consider USD search path env variable on read for mtlx (partial, no concensus) (PR 1628)
| | load / reload | Robustness / repeatability of loading documents |
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| - Issue 1504 logged. Internal issue: USD-6670 (data loss)
- Issue 1502 logged. Internal issue: USD-6669 (node missing)
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Current list of all MaterialX related issues (not all applicable)
https://github.com/PixarAnimationStudios/USD/issues?q=is%3Aissue+is%3Aopen+Materialx
Unsupported Documentation notes (appears notes are from 1.37)
https://graphics.pixar.com/usd/docs/api/usd_mtlx_page_front.html#usdMtlx_unsupported
Appendix: Examples
Namespaces and Versioning
https://github.com/autodesk-forks/MaterialX/blob/adsk_contrib/dev/resources/Materials/TestSuite/adsklib/archviz/adsk_metal.mtlx
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