microfacetrelated

Microfacet theory is a surface rendering model used in computer graphics to simulate the way light interacts with rough surfaces. It proposes that a macroscopic surface is composed of many tiny, idealized, mirror-like surfaces called microfacets. These microfacets are randomly oriented, and their collective behavior determines how light reflects off the overall surface. The distribution of these microfacet orientations is crucial and is described by a function known as the normal distribution function (NDF).

When light strikes a surface, according to microfacet theory, it reflects off individual microfacets according to the law of reflection. The overall appearance of the surface, such as its shininess and the way it scatters light, is then an aggregation of the reflections from all these microfacets. A key aspect is that the incoming light ray and outgoing view ray are reflected by a microfacet whose normal bisects the angle between them.

This model is particularly effective at capturing the specular reflection component of rendering, explaining phenomena like Fresnel reflections and the appearance of highlights. Different NDFs can be used to represent various surface roughnesses, from very smooth and mirror-like to rough and diffuse. Common NDFs include the Beckmann, GGX (Trowbridge-Reitz), and Blinn-Phong models, each offering different trade-offs in terms of visual realism and computational cost. Microfacet theory has become a cornerstone of physically based rendering (PBR) due to its ability to produce realistic and physically plausible surface appearances.