Tessellation-Independent Smooth Shadow Boundaries

Oliver Mattausch, Daniel Scherzer, Michael Wimmer, Takeo Igarashi
Tessellation-Independent Smooth Shadow Boundaries
Computer Graphics Forum, 4(31):1465-1470, June 2012. [draft]

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Abstract

We propose an efficient and light-weight solution for rendering smooth shadow boundaries that do not reveal the tessellation of the shadow-casting geometry. Our algorithm reconstructs the smooth contours of the underlying mesh and then extrudes shadow volumes from the smooth silhouettes to render the shadows. For this purpose we propose an improved silhouette reconstruction using the vertex normals of the underlying smooth mesh. Then our method subdivides the silhouette loops until the contours are sufficiently smooth and project to smooth shadow boundaries. This approach decouples the shadow smoothness from the tessellation of the geometry and can be used to maintain equally high shadow quality for multiple LOD levels. It causes only a minimal change to the fill rate, which is the well-known bottleneck of shadow volumes, and hence has only small overhead.

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BibTeX

@article{MATTAUSCH-2012-TIS,
  title =      "Tessellation-Independent Smooth Shadow Boundaries",
  author =     "Oliver Mattausch and Daniel Scherzer and Michael Wimmer and
               Takeo Igarashi",
  year =       "2012",
  abstract =   "We propose an efficient and light-weight solution for
               rendering smooth shadow boundaries that do not reveal the
               tessellation of the shadow-casting geometry. Our algorithm
               reconstructs the smooth contours of the underlying mesh and
               then extrudes shadow volumes from the smooth silhouettes to
               render the shadows. For this purpose we propose an improved
               silhouette reconstruction using the vertex normals of the
               underlying smooth mesh. Then our method subdivides the
               silhouette loops until the contours are sufficiently smooth
               and project to smooth shadow boundaries. This approach
               decouples the shadow smoothness from the tessellation of the
               geometry and can be used to maintain equally high shadow
               quality for multiple LOD levels. It causes only a minimal
               change to the fill rate, which is the well-known bottleneck
               of shadow volumes, and hence has only small overhead. ",
  month =      jun,
  issn =       "1467-8659",
  journal =    "Computer Graphics Forum",
  number =     "31",
  volume =     "4",
  pages =      "1465--1470",
  keywords =   "real-time rendering, shadows",
  URL =        "https://www.cg.tuwien.ac.at/research/publications/2012/MATTAUSCH-2012-TIS/",
}