Rendering realistic skin has always been a challenge in computer graphics. Human observers are particularly sensitive to the appearance of faces and skin, and skin exhibits several complex visual characteristics that are difficult to capture with simple shading models. One of the defining characteristics of skin is the way light bounces around in the dermis and epidermis layers. When rendering using a simple diffuse model, the light is assumed to immediately bounce equally in all directions after striking the surface. While this is very fast to compute, it gives surfaces a very “thin” and “hard” appearance. In order to make skin look more “soft” it is necessary to take into account the way light bounces around inside a surface. This phenomenon is known as subsurface scattering, and substantial recent effort has been spent on the problem of realistic, real-time rendering with accurate subsurface scattering.