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.