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Fix metallic F90 in UsdPreviewSurface #1187

Merged
merged 1 commit into from
Jan 5, 2023
Merged

Fix metallic F90 in UsdPreviewSurface #1187

merged 1 commit into from
Jan 5, 2023

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jstone-lucasfilm
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This changelist fixes the computation of F90 in the metallic workflow of UsdPreviewSurface.

This aligns the MaterialX graph for UsdPreviewSurface with its specification (https://graphics.pixar.com/usd/release/spec_usdpreviewsurface.html), which states:

"If metallic is 1, then both F0 (reflectivity at 0 degree incidence) and edge F90 reflectivity will simply be the Albedo. If metallic is 0, then Albedo is ignored in the calculation of F0 and F90; F0 is derived from ior via ((1-ior)/(1+ior))^2 and F90 is white. In between, we interpolate."

This changelist fixes the computation of F90 in the metallic workflow of UsdPreviewSurface.

This aligns the MaterialX graph for UsdPreviewSurface with its specification (https://graphics.pixar.com/usd/release/spec_usdpreviewsurface.html), which states:

"If metallic is 1, then both F0 (reflectivity at 0 degree incidence) and edge F90 reflectivity will simply be the Albedo. If metallic is 0, then Albedo is ignored in the calculation of F0 and F90; F0 is derived from ior via ((1-ior)/(1+ior))^2 and F90 is white. In between, we interpolate."
@jstone-lucasfilm
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Thanks to @klucknav and @spiffmon for noting this issue, and I'm additionally CC'ing @pablode for his thoughts on this proposed change.

@jstone-lucasfilm jstone-lucasfilm merged commit c58bbfb into AcademySoftwareFoundation:main Jan 5, 2023
Michaelredaa pushed a commit to Michaelredaa/MaterialX that referenced this pull request Oct 21, 2023
This changelist fixes the computation of F90 in the metallic workflow of UsdPreviewSurface.

This aligns the MaterialX graph for UsdPreviewSurface with its specification (https://graphics.pixar.com/usd/release/spec_usdpreviewsurface.html), which states:

"If metallic is 1, then both F0 (reflectivity at 0 degree incidence) and edge F90 reflectivity will simply be the Albedo. If metallic is 0, then Albedo is ignored in the calculation of F0 and F90; F0 is derived from ior via ((1-ior)/(1+ior))^2 and F90 is white. In between, we interpolate."
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