title =      "Fast Accurate Soft Shadows with Adaptive Light Source
  author =     "Michael Schw{\"a}rzler and Oliver Mattausch and Daniel
               Scherzer and Michael Wimmer",
  year =       "2012",
  abstract =   "Physically accurate soft shadows in 3D applications can be
               simulated by taking multiple samples from all over the area
               light source and accumulating them. Due to the
               unpredictability of the size of the penumbra regions, the
               required sampling density has to be high in order to
               guarantee smooth shadow transitions in all cases. Hence,
               several hundreds of shadow maps have to be evaluated in any
               scene configuration, making the process computationally
               expensive.   Thus, we suggest an adaptive light source
               subdivision approach to select the sampling points
               adaptively. The main idea is to start with a few samples on
               the area light, evaluating there differences using hardware
               occlusion queries, and adding more sampling points if
               necessary. Our method is capable of selecting and rendering
               only the samples which contribute to an improved shadow
               quality,  and hence generate shadows of comparable quality
               and accuracy.  Even though additional calculation time is
               needed for the comparison step, this method saves valuable
               rendering time and achieves interactive to real-time frame
               rates in many cases where a brute force sampling method does
  pages =      "39--46",
  month =      nov,
  booktitle =  "Proceedings of the Vision, Modeling, and Visualization
               Conference (VMV 2012)",
  keywords =   "soft shadows, real-time rendering"