title =      "Real-Time Soft Shadows Using Temporal Coherence",
  author =     "Daniel Scherzer and Michael Schw{\"a}rzler and Oliver
               Mattausch and Michael Wimmer",
  year =       "2009",
  abstract =   "A vast amount of soft shadow map algorithms have been
               presented in recent years. Most use a single sample hard
               shadow map together with some clever filtering technique to
               calculate perceptually or even physically plausible soft
               shadows.   On the other hand there is the class of much
               slower algorithms that calculate physically correct soft
               shadows by taking and combining many samples of the light. 
               In this paper we present a new soft shadow method that
               combines the benefits of these approaches. It samples the
               light source over multiple frames instead of a single frame,
               creating only a single shadow map each frame. Where temporal
               coherence is low we use spatial filtering to estimate
               additional samples to create correct and very fast soft
               shadows. ",
  pages =      "13--24",
  month =      dec,
  booktitle =  "Advances in Visual Computing: 5th International Symposium on
               Visual Computing (ISVC 2009)",
  isbn =       "978-3642103308",
  series =     "Lecture Notes in Computer Science",
  publisher =  "Springer",
  location =   "Las Vegas, Nevada, USA",
  keywords =   "real-time rendering, soft shadows"