Fast Accurate Soft Shadows with Adaptive Light Source Sampling

Michael Schwärzler, Oliver Mattausch, Daniel Scherzer, Michael Wimmer
Fast Accurate Soft Shadows with Adaptive Light Source Sampling
In Proceedings of the 17th International Workshop on Vision, Modeling, and Visualization (VMV 2012), pages 39-46. November 2012.
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Information

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 not.

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BibTeX

@inproceedings{SCHWAERZLER-2012-FAS,
  title =      "Fast Accurate Soft Shadows with Adaptive Light Source
               Sampling",
  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
               not. ",
  month =      nov,
  booktitle =  "Proceedings of the 17th International Workshop on Vision,
               Modeling, and Visualization (VMV 2012)",
  isbn =       "978-3-905673-95-1",
  location =   "Magdeburg, Germany",
  publisher =  "Eurographics Association",
  pages =      "39--46",
  keywords =   "soft shadows, real-time rendering",
  URL =        "https://www.cg.tuwien.ac.at/research/publications/2012/SCHWAERZLER-2012-FAS/",
}