Jean-François St-Amour Eric Paquette Pierre Poulin Soft shadows from extended light sources with penumbra deep shadow maps. 105-112 2005 conf/graphicsinterface/2005 Graphics Interface http://doi.acm.org/10.1145/1089508.1089526 db/conf/graphicsinterface/graphicsinterface2005.html#St-AmourPP05