ABSTRACT
The general BRDF approach to modeling surface light reflection implicitly assumes that light is reflected immediately at the intersection point. In reality, however, some of the incident light penetrates the object, bounces around below the surface, then emerges at some different point. This behavior is called subsurface scattering. While most materials in the real world exhibit some amount of subsurface scattering, it is a significant part of the appearance of translucent materials such as marble, milk, and skin.
