Design Nomenclature / Surface & Material
Microfacet
Also called microfacet model, microfacet distribution, ggx
The modeling assumption that a surface too small to resolve is a field of perfect mirrors, described statistically by a normal distribution (GGX, Beckmann), a shadowing-masking term accounting for facets blocking each other, and a Fresnel term. Every physically based specular lobe anyone has ever tuned is this abstraction.
Not to be confused with
- Bump mapA grayscale texture read as height, from which the shader derives a normal perturbation by differencing neighboring texels. Encodes the same end result as a normal map at lower precision and without the ability to state direction independently of slope. Cheap, lossy, and still the right call for fine noise.
- Normal mapA texture encoding a perturbed shading normal per texel, XYZ packed into RGB, usually in tangent space so it survives deformation. It changes the vector lighting is computed against without moving a single vertex, so silhouettes stay flat, nothing self-shadows, and the whole illusion fails at grazing angles.