Volumetric Methods for Simulation and Rendering of Hair

Hair is one of the crucial elements in representing believable digital humans. It is one of the most challenging elements, too, due to the large number of hairs on a human head, their length, and their complex interactions. Hair appearance, in rendering and simulation, is dominated by collective properties, yet most of the current approaches model individual hairs. In this paper we build on the existing approaches to illumination and simulation by introducing a volumetric representation of hair which allows us to efficiently model collective properties of hair. We use this volumetric representation of hair to describe hair response to illumination, hair to hair collisions, and to subtly direct simulations of hair. Our method produces realistic results for different types of hair colors and styles and has been used in a production environment.