Microfacet Model

Computer Graphics · Materials and BSDFs · 2007 · microfacet-model.yaml

Treats a rough surface as a statistical field of tiny perfect mirrors. The BSDF factors into a normal distribution D, a Fresnel term F and a masking-shadowing term G, and nearly every modern material model is an instance of it.

• supersedescorrects · extends
• classifiesspecializes · part-of
• substitutes forapproximates · alternative-to
• depends onrequires · validates

Colour is the family; a dashed line is the second member of it.

This node

• specializesis a specific case of BSDFderives the BSDF from a statistical surface model
• requiresdoes not work without Fresnel Equationseach microfacet is a mirror, so needs its reflectance
• requiresdoes not work without Smith Masking-Shadowingmicrofacets occlude each other at grazing angles

Referenced by

• specializesBeckmann Distribution is a specific case of thissupplies a Gaussian slope distribution as D
• specializesCook-Torrance is a specific case of thisfirst graphics-side instance of the framework
• specializesDisney Principled BRDF is a specific case of thiswraps it in parameters artists can actually author
• specializesGGX / Trowbridge-Reitz is a specific case of thissupplies a long-tailed slope distribution as D
• extendsCoated Layer Model adds capability to thismicrofacet layers stacked into a single BSDF
• approximatesLinearly Transformed Cosines is a cheaper stand-in for thismakes area-light integrals closed form
• part-ofSmith Masking-Shadowing is a subtopic of this
• approximatesSplit-Sum Approximation is a cheaper stand-in for thissplits the integral into two precomputable factors
• part-ofTorrance-Sparrow is a subtopic of this

References

• Microfacet Models for Refraction through Rough Surfaces — Walter, Marschner, Li, Torrance — 2007 · link
• Background — Specular highlight on Wikipedia