ABSTRACT
This chapter discusses some of the most visually important aspects of material properties and a few fairly simple models that are useful in capturing these properties. There are many Bidirectional reflectance distribution function (BRDF) models in use in graphics, and the models presented here are meant to give just an idea of nondiffuse BRDFs. The chapter defines some categories of materials. It presents reflection models that target each type of material. Reflection in matte/specular materials, such as plastics or polished woods, is governed by Fresnel equations at the surface and by scattering within the subsurface. This effect causes the vertically streaked reflections seen on lakes on windy days; it can either be modeled using explicit microgeometry and a simple smooth-surface reflection model or by a more general model that accounts for this asymmetry.
