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

Daniel Scherzer, Stefan Jeschke, Michael Wimmer
Pixel-Correct Shadow Maps with Temporal Reprojection and Shadow Test Confidence
In Rendering Techniques 2007 (Proceedings Eurographics Symposium on Rendering), pages 45-50. June 2007.
[Preprint]

Information

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.

Additional Files and Images

Additional images and videos

image1: Pixel-correct shadow maps as a result of using a shadow map (size 10242) with shadow test confidence together with a history buffer. Note that projection and perspective aliasing are completely removed.
image2: In this figure we used our new shadow mapping technique (PCSM) toshow that even scenarios were projection aliasing is the dominant source of error, we can produce the correct shadowing solution.
image3: In this figure we used our new shadow mapping technique (PCSM) toshow that even scenarios were projection aliasing is the dominant source of error, we can produce the correct shadowing solution.
image4: New fragments (shown in red) without history that result from a camera translation.

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BibTeX

@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.",
  month =      jun,
  booktitle =  "Rendering Techniques 2007 (Proceedings Eurographics
               Symposium on Rendering)",
  editor =     "Jan Kautz and Sumanta Pattanaik",
  isbn =       "978-3-905673-52-4",
  location =   "Grenoble, France",
  organization = "Eurographics",
  publisher =  "Eurographics Association",
  pages =      "45--50",
  keywords =   "shadow mapping",
  URL =        "https://www.cg.tuwien.ac.at/research/publications/2007/Scherzer-2007-PCS/",
}