On Making Light Maps Dynamic

László Szécsi and László Szirmay-Kalos
Department of Control Engineering and Information Technology, Technical University of Budapest,
Budapest, Magyar Tudósok krt. 2, HUNGARY


This paper presents a real-time global illumination method for static scenes illuminated by arbitrary, dynamic light sources. The method consists of a preprocessing phase and a real-time rendering phase. The real-time rendering algorithm obtains the indirect illumination caused by the multiple scattering of the light from partial light paths that are precomputed and stored in the preprocessing phase. The starting points of partial light paths are called entry points and are sampled randomly on the surfaces. The end points of partial light paths, called exit points, correspond to texel centers of a texture atlas. During preprocessing the radiance of exit points are determined assuming that the entry point has unit irradiance, and the results are stored in texture maps, called Pre- computed Radiance Maps. Precomputed Radiance Maps represent the self-illumination capabilities of the whole scene. Introducing light sources and the camera in the real-time animation phase, the direct illumination of the real light sources can be computed by evaluating local illumina- tion at the entry points. Modulating the Precomputed Radiance Maps by the obtained entry point irradiance values, the indirect illumination due to multiple re°ections can be calculated at the exit points. Adding the direct illumination, the global illumination solution can be obtained instantly even when the camera or the light sources move. The role of the proposed method in games and interactive applications is similar to that of light maps. It also renders indirect lighting of static geometry, but unlike light maps, it allows for dynamic lighting and updates indirect shadows and color bleeding e®ects when light sources move..