Tobias Ritschel Thorsten Grosch Jan Kautz Hans-Peter Seidel Interactive global illumination based on coherent surface shadow maps. 185-192 2008 Graphics Interface http://doi.acm.org/10.1145/1375714.1375747 conf/graphicsinterface/2008 db/conf/graphicsinterface/graphicsinterface2008.html#RitschelGKS08