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AcademySoftwareFoundation / OpenPBR

Specification and reference implementation for the OpenPBR Surface shading model
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Coat and Fuzz parameter order inconsistent between specification and reference implementation #223

Open JGamache-autodesk opened 1 month ago

JGamache-autodesk commented 1 month ago

Clearly a very minor detail, but the reference implementation has Fuzz before Coat while the specification has Coat before Fuzz in the parameter reference.

JGamache-autodesk commented 1 month ago

The Emission and Thin Film sections are also swapped between spec and reference implementation.

portsmouth commented 1 month ago

I think coat before fuzz makes more sense for OpenPBR, since we generally order the parameters from the base upwards.

Having emission before thin-film (and thin-film after fuzz) doesn't seem particularly logical though. Arguably the emission should be just before the coat (since the coat tints the emission):

We put emission below the coating so that emitted light will be tinted due to the absorption in the coat and fuzz layers.

And the thin-film should be just before the emission, since it lies above the base, but does not tint the emission.