Surface shading of computer-generated object using multiple surfaces

Abstract

Objects are modeled and rendered using multiple surfaces to provide attributes used in rendering. In some embodiments, a reference surface for an object is defined, e.g., using conventional modeling techniques. One or more auxiliary surfaces are associated with portions of the reference surface. Some of the surface attributes (e.g., color, surface normal, texture, lighting) are associated with the reference surface, while other attributes (e.g., transparency) are associated with the cards. To render an image, a ray associated with a pixel is traced to its intersection with the reference surface and to its intersection with one of the auxiliary surfaces. The attributes associated with the reference surface are determined based on the intersection point of the ray with the reference surface, and the attributes associated with the auxiliary surface are determined based on the intersection point of the ray with the auxiliary surface.