Applies thin film iridescence to metals in Metallic BSDF and Principled BSDF.
To get the complex IOR values for each spectral band from F82 Tint colors,
the code uses the parametrization from "Artist Friendly Metallic Fresnel",
where the g parameter is set to F82. This IOR is used to find the phase shift,
but reflectance is still calculated with the F82 Tint formula after adjusting
F0 for the film's IOR.
Co-authored-by: Lukas Stockner <lukas@lukasstockner.de>
Co-authored-by: Weizhen Huang <weizhen@blender.org>
Co-authored-by: RobertMoerland <rmoerlandrj@gmail.com>
Pull Request: https://projects.blender.org/blender/blender/pulls/141131
2bd06093c7