A reflectance model for producing realistic images of rough surfaces by means of computer graphics developed by Robert Cook in 1981. Reflectance models describe both the color and the spatial distribution of reflected light. The bidirectional reflection model predicts the directional distribution and spectral composition of the reflected light. This is split into two components that represent the light reflected from the surface of the material and a diffuse component that is dependent on the nature of the surface. Bidirectional reflection distribution was one of the first models to render images that could look plastic or metallic depending on the parameters of the surface.