Real-time Soft Shadows with Shadow Accumulation

Abstract

This paper presents a physically plausible soft-shadow algorithm that can be executed real-time by current GPUs. The method works with a single shadow map, requires no pre- or post-processing, and can also handle self shadowing. The main novelty of the method is in the interpretation of the shadow map. A lexel with depth information is considered as the geometric definition of an elementary shadow caster. When the shadowing of a point is computed, the algorithm decides whether these elementary casters occlude the light source area from the shaded point, and the shadowing factors of the elementary casters are accumulated.