Illumination Models

The application of research in physics and optics to computer graphics constitutes an evolution governed by the current visible surface algorithms, by what is considered computationally reasonable, and by the level of realism that is acceptable. The illumination models used in practice differ greatly from the theoretical treatment of Chapter 2. The illumination models used fall into three general classifications: empirical, transitional, and analytical. The shading techniques that evolved with these models fall into three corresponding classifications: incremental, ray tracing, and radiosity methods, Table 4.1. In addition, a hybrid classification has recently emerged that combines the radiosity and ray tracing approaches.