Physically based lighting calculations for computer graphics

Realistic image generation is presented in a theoretical formulation that builds from previous work on the rendering equation. Previous and new solution techniques for the global illumination are discussed in the context of this formulation. The physical rules governing reflection are used to make improvements in local reflection models. The conventional local illumination models used in computer graphics are examined and modified to be consistent with these physical rules. Global illumination is treated in terms of evaluation of a Global Radiance Function. Image-based solution methods are phrased as a lazy evaluation of the Global Radiance Function; evaluation takes place for visible points. Zonal solution methods are phrased as table based solutions. A proof is given that, subject to certain constraints, only O(N) rays are required for a zonal solution with N zones. Simulation allows for surfaces which are not zoned to interact with those that are. The ray tracing zonal solution methods used for surfaces are extended to scenes with participating media. The impact of wavelength selection and time dependencies is also discussed. An object oriented implementation is discussed. This implementation separates the local and global illumination modules, so all of the specifics of the local models are hidden from the global energy transport code. This allows new local modules to be added by specifying the black box access routines.