About 3.5 years ago I did some experiment to improve the behavior of microfacet normals at glancing angles. Many surfaces become highly reflective even though having high roughness. Check the discussion in the thread. Here is my implementation reusing equations you already have:
Max Liani
There's a neat short paper from Eurographics this year that evaluates how well microfacet shading models actually predict measured reflectance. The answer is: not nearly as well as one would hope!
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ssteinberg.xyz/2026_surface...
