term. G is the geometric attenuation term, describing selfshadowing due to the microfacets, and is of the form . In these formulas V is the vector to the camera or eye, H is the half-angle vector, L is the vector to the light source and N is the normal vector, and α is the angle between H and N. Using multiple distributions If desired, different distributions (usually, using the same distribution function with different values of m or n) can be combined using a weighted average. This is useful for modelling, for example, surfaces that have small smooth and rough patches rather than uniform roughness. See also List of common shading algorithms Specular reflection Diffuse reflection Gamma correction Fresnel equations Retroreflector Reflection (physics) Refraction Specularity References Imaging Shading