Improved open_pbr_surface to standard_surface translation
#1958
Conversation
Revising base and subsurface color calculations to more closely resemble coat_darkening present in OpenPBR
reformatting
removing redundant ifgreater node for subsurface color calculation
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Pearl comparisons:
Generated difference images between the Standard Surface image and the OpenPBR image for both versions. The original average difference was 0.92 (out of 255), and the new average difference is 0.57. |
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Carpaint comparisons:
Generated difference images between the Standard Surface image and the OpenPBR image for both versions. The original has an average difference of 1.57 (out of 255), and the new one has an average difference of 1.21.
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jstone-lucasfilm
changed the title
open_pbr_surface to standard_surface translationopen_pbr_surface to standard_surface translation
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I see, so this bakes in the darkening factor into the The way we translate should depend on what the intended usage of the translated shader is. If it is assumed to be baked and immutable, then this kind of baking of the darkening is fine. But if the user might want to change the parameters after the translation (e.g. remove coat etc.), then it would be better to try to reproduce the structure as well as possible, e.g. keep the base color and just use the I'm not sure what the more appropriate policy would be for these translation graphs. |
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Thanks for these notes, @portsmouth! In my own experience, the most important quality of a shader translation graph is its visual parity, since the majority of the artistic work on the material usually occurs before shader translation is applied, and the receiving party is most interested in rendering the original material as accurately as possible. In situations where additional edits are needed, it's also possible to share the unbaked translated graph, in which the original shading model interface of the material remains available for further editing, though in practice it's more common to bake out textures and constant values in the new shading model. From this perspective, I would consider @mkuo-lucasfilm's latest work to be a meaningful improvement, since there's a small but measurable improvement to parity for coated materials, and no reduction of parity for other materials. |
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Let's move forward with this refinement to the shader translation graph, and there's still time for additional improvements before the release of MaterialX 1.39.1. Thanks for your great work on this, @mkuo-lucasfilm! |
jstone-lucasfilm
merged commit 1775a6d
into
AcademySoftwareFoundation:main
…Foundation#2087) The standard_surface coat parameters are currently affecting the baseColor of UsdPreviewSurface. It should also affect emission color. Initial translation from `open_pbr_surface` to `standard_surface` (AcademySoftwareFoundation#1949) - Authored an initial pass at the translation from OpenPBR to standard surface. - This would help to support OpenPBR in applications using earlier versions of MaterialX, which only have access to Standard Surface, but may want to participate in the OpenPBR ecosystem before they upgrade. Update `standard_surface` to `open_pbr` translation graph (AcademySoftwareFoundation#1956) Replacing coat_affect_roughness with a constant value, since a coating always affects roughness in OpenPBR and is not dependent on the value of coat_darkening. Improved `open_pbr_surface` to `standard_surface` translation (AcademySoftwareFoundation#1958) Integrated the logic of coat_darkening from OpenPBR into the calculations of base_color and subsurface_color. Initial translation from `standard_surface` to `open_pbr_surface` (AcademySoftwareFoundation#1934) 1. Authored an initial pass at the translation graph between standard surface and OpenPBR 2. Added units to standard surface thin film thickness documentation Update documentation of OpenPBR and Standard Surface translations (AcademySoftwareFoundation#1963) Clarified documentation where the motivation for the conversion might not be clear - both for the translation graph from OpenPBR to Standard Surface, and the translation graph from Standard Surface to OpenPBR. Decrement translation graphs minor version (backport) Consider subsurface color in dielectric albedo
Integrated the logic of coat_darkening from OpenPBR into the calculations of base_color and subsurface_color