Pixel-Correct Shadow Maps with Temporal Reprojection and Shadow Test Confidence

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• Publication Type: Conference Paper
• Date (from): 25.6.2007
• Date (to): 27.6.2007
• Editor: Jan Kautz and Sumanta Pattanaik
• ISBN: 978-3-905673-52-4
• Lecturer: Daniel Scherzer
• Location: Grenoble, France
• Organization: Eurographics
• Publisher: Eurographics Association
• Keywords: shadow mapping

This paper extends shadow mapping by reusing information of previously rasterized images, stored efficiently in a so-called history buffer. This buffer is updated in every frame and then used for the shadow calculation. In combination with a special confidence-based method for the history buffer update (based on the current shadow map), temporal and spatial aliasing can be completely removed. The algorithm converges in about 10 to 60 frames and during convergence, shadow borders are sharpened over time. Consequently, in case of real-time frame rates, the temporal shadow adaption is practically imperceptible. The method is simple to implement and is as fast as uniform shadow mapping, incurring only the minor speed hit of the history buffer update. It works together with advanced filtering methods like percentage closer filtering and more advanced shadow mapping techniques like perspective or light space perspective shadow maps.

@inproceedings\{Scherzer-2007-PCS,
  title =      "Pixel-Correct Shadow Maps with Temporal Reprojection and 
               Shadow Test Confidence",
  author =     "Daniel Scherzer and Stefan Jeschke and Michael Wimmer",
  year =       "2007",
  abstract =   "Shadow mapping suffers from spatial aliasing (visible as
               blocky shadows) as well as temporal aliasing (visible as
               flickering). Several methods have already been proposed for
               reducing such artifacts, but so far none is able to provide
               satisfying results in real time.  This paper extends shadow
               mapping by reusing information of previously rasterized
               images, stored efficiently in a so-called history buffer.
               This buffer is updated in every frame and then used for the
               shadow calculation. In combination with a special
               confidence-based method for the history buffer update (based
               on the current shadow map), temporal and spatial aliasing
               can be completely removed. The algorithm converges in about
               10 to 60 frames and during convergence, shadow borders are
               sharpened over time. Consequently, in case of real-time
               frame rates, the temporal shadow adaption is practically
               imperceptible. The method is simple to implement and is as
               fast as uniform shadow mapping, incurring only the minor
               speed hit of the history buffer update. It works together
               with advanced filtering methods like percentage closer
               filtering and more advanced shadow mapping techniques like
               perspective or light space perspective shadow maps.",
  pages =      "45--50",
  month =      jun,
  isbn =       "978-3-905673-52-4",
  location =   "Grenoble, France",
  editor =     "Jan Kautz and Sumanta Pattanaik",
  booktitle =  "Rendering Techniques 2007 (Proceedings Eurographics
               Symposium on Rendering)",
  organization = "Eurographics",
  publisher =  "Eurographics Association",
  keywords =   "shadow mapping",
  URL =        "http://www.cg.tuwien.ac.at/research/publications/2007/Scherzer-2007-PCS/",
}