Real-time Soft Shadows with Shadow Accumulation

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


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.


Soft shadow, shader programming.