Improved Computation of Attenuated Light with Application in Scenes with Many Light Sources

This paper presents and investigates methods for fast and accurate illumination of scenes containing many light sources that have limited spatial influence, e.g. point light sources. For speeding up the computation, current graphics applications use an assumption that the light sources range can be limited using bounding spheres due to their limited spatial influence and illumination is computed only if a surface lies within the sphere. Therefore, we explore the differences in illumination between scenes illuminated with spatially limited light sources and physically more correct computation where the light radius is infinite. We show that the difference can be small if we add appropriate ambient lighting. The contribution of the paper is the method for fast estimation of ambient lighting in scenes illuminated by numerous light sources. We also propose a method for elimination of color discontinuities at the edges of the bounding spheres. Our solution is tested on two different scenes: a procedurally generated city and the Sibenik cathedral. Our approach allows for correct lighting computation in scenes with numerous light sources without any modification of the scene graph or other data structures or rendering procedures. It thus can be applied in various systems without any structural modifications.