Bidirectional Reflection Distribution Functions from Surface Bump Maps.

摘要

The interaction of light and matter defines what we see. This interaction can be characterized by a function which relates incoming light to the distribution of outgoing or reflected light. The Bidirectional Reflection Distribution Function (BRDF) is just such a function. Computer graphics scientists attempting to model this function have made simplifying assumptions about the reflecting surfaces. These simpler models have produced adequate results but only handle very uniform or isotropic surface characteristics. Reality on the other hand is filled with a variety of surface textures which result in a variety of BRDFs. This thesis broadens the class of BRDFs which can be used in computer graphics to render objects more realistically. It presents two enhancements to previous work done by the author. First, it describes a method for the approximation of surface absorption of light through the use of a computed geometric attenuation factor. This factor is computed by calculating the parts of the surface which are visible in the incident and reflecting directions. Specifically, it describes the algorithms and theory behind the visibility calculations and how it affects the reflection properties of the surface. Second, it describes a method for computing Fresnel's Law for conducting and dielectric surface materials and how Fresnel's Law affects surface reflectivity. This work also presents a method for rendering objects using the computed BRDFs. 38 refs., 29 figs., 2 tabs.