ABSTRACT
IN TRADITIONAL COMPUTER GRAPHICS, 3D objects are created using highlevel surface representations such as polygonal meshes, NURBS (nonuniform rational B-spline) patches, or subdivision surfaces. Using this modeling paradigm, visual properties of surfaces, such as color, roughness, and reflectance, are described by means of a shading algorithm, which might be as simple as the Lambertian diffuse reflection model or as complex as a fully-featured shift-variant anisotropic BRDF.1 Because light transport is evaluated only at points on the surface, these methods usually lack the ability to account for light interaction that takes place in the atmosphere or in the interior of an object.
