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AcademySoftwareFoundation / OpenPBR

Specification and reference implementation for the OpenPBR Surface shading model
Apache License 2.0
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Thin film in micrometers divided by 2 for normalized parameter range #150

Closed sharktacos closed 2 months ago

sharktacos commented 7 months ago

Currently thin film has a range of 0-2000 nanometers. I'd like to propose for discussion instead measuring in micrometers which would be 0-2 range, and then dividing that by 2 in order to have a normalized 0-1 parameter range. This makes a more artist friendly slider.

portsmouth commented 5 months ago

I like this, the existing requirement to input a length in nm seems a bit obscure to me.

portsmouth commented 5 months ago

Also, it's unclear from the spec how the thin_film_ior interacts with the IORs of the surrounding media. Should the thin-film effect disappear if its IOR equals the coat IOR for example? (Physically, presumably yes, but in implementations I've seen it currently doesn't).

portsmouth commented 5 months ago

A related proposal is to add a thin_film_weight parameter in [0,1], which will just blend the effect in and out. If we had that, keeping the width parameter in physical units might be more reasonable.

https://github.com/AcademySoftwareFoundation/OpenPBR/issues/134

jstone-lucasfilm commented 2 months ago

Thanks for this original report, @sharktacos, and it's now addressed in #167.