ABSTRACT
The fundamental transport equation used to describe the global illumination problem is called the rendering equation. The rendering equation describes the transport of radiance through a three-dimensional environment. It is the integral equation formulation of the definition of the BRDF and adds the self-remittance of surface points at light sources as an initialization function. The Global Reflectance Distribution Function (GRDF) allows us to describe the global illumination problem in a very short and elegant format, independent of any initial distributions for self–-emitted radiance or importance. The GRDF is only dependent on the geometry of the scene and the reflective properties of the surfaces. Both the transport of radiance and importance can be combined by introducing the global reflectance distribution function. The GRDF describes a general transfer property from one point–-direction pair in the scene to another point-direction pair. As such, it can be considered as the core function for the global illumination problem.
