use the un-linearized lambert transparency to author displayOpacity when using displayColors shading mode #751
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… where it is used
Prior to PR Autodesk#707, the un-linearized transparency value was being used to compute a transparency "average", which was then used to author displayOpacity on the bound gprim if it did not already have an authored displayOpacity, as well as a displayOpacity input on the shader prim. It looks like an unintended side effect of Autodesk#707 was that it was made to use the linearized transparency for this purpose instead. Both of these behaviors seem somewhat dubious. It doesn't really seem like the shading mode exporter should be authoring displayOpacity of the bound gprim, since that is more a property of the geometry than the material. It also doesn't appear as if the displayOpacity input being authored on the shader prim is used for anything. Ignoring those two oddities for now, the changes here should address the "regression" introduced by Autodesk#707. We can revisit the behavior of the displayColors shading mode (or better yet work towards removing it!) in follow-up commits.
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Prior to PR #707, the un-linearized transparency value was being used to compute a transparency "average", which was then used to author
displayOpacityon the bound gprim if it did not already have an authoreddisplayOpacity, as well as adisplayOpacityinput on the shader prim. It looks like an unintended side effect of #707 was that it was made to use the linearized transparency for this purpose instead. Note the use of the linearizedtransparencyinstead of the previously un-linearizedmayaTransparencyhere:https://github.com/Autodesk/maya-usd/pull/707/files#diff-5fe2e05011c04068f0f7249a36061532R138
Both of these behaviors seem somewhat dubious. It doesn't really seem like the shading mode exporter should be authoring
displayOpacityof the bound gprim, since that is more a property of the geometry than the material. It also doesn't appear as if thedisplayOpacityinput being authored on the shader prim is used for anything.Ignoring those two oddities for now, the changes here should address the "regression" introduced by #707. We can revisit the behavior of the displayColors shading mode (or better yet work towards removing it!) in follow-up commits.