Interactive Smooth and Curved Shell Mapping

Stefan Jeschke, Stephan Mantler, Michael Wimmer
Interactive Smooth and Curved Shell Mapping
In Rendering Techniques 2007 (Proceedings Eurographics Symposium on Rendering), pages 351-360. June 2007.
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Abstract

Shell mapping is a technique to represent three-dimensional surface details. This is achieved by extruding the triangles of an existing mesh along their normals, and mapping a 3D function (e.g., a 3D texture) into the resulting prisms. Unfortunately, such a mapping is nonlinear. Previous approaches perform a piece-wise linear approximation by subdividing the prisms into tetrahedrons. However, such an approximation often leads to severe artifacts. In this paper we present a correct (i.e., smooth) mapping that does not rely on a decomposition into tetrahedrons. We present an efficient GPU ray casting algorithm which provides correct parallax, self-occlusion, and silhouettes, at the cost of longer rendering times. The new formulation also allows modeling shells with smooth curvatures using Coons patches within the prisms. Tangent continuity between adjacent prisms is guaranteed, while the mapping itself remains local, i.e. every curved prism content is modeled at runtime in the GPU without the need for any precomputation. This allows instantly replacing animated triangular meshes with prism-based shells.

Additional Files and Images

Additional images and videos:
cube cube: A shell-mapped cube
EnvMapI EnvMapI: A shell-mapped and environment-mapped sphere
EnvMapII EnvMapII: Closeup of a shell-mapped and environment-mapped sphere
Mapping Mapping: Mapping between prisms in texture and world space
shadow shadow: Correct shadowing with shell mapping
teapots teapots: Shell mapped teapot with different textures
tiger tiger: Tiger model with a furry shell map
torus torus: A shell-mapped torus
torusinside torusinside: Inside view in a torus with different shell maps applied
TorusSmoothCurved TorusSmoothCurved: Shell mapped torus. Left: smooth mapping. Right: curved mapping.
More images and videos:
video
video

Additional files:
additional images
additional images




BibTeX

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@inproceedings{JESCHKE-2007-ISC,
  title =      "Interactive Smooth and Curved Shell Mapping",
  author =     "Stefan Jeschke and Stephan Mantler and Michael Wimmer",
  year =       "2007",
  abstract =   "Shell mapping is a technique to represent three-dimensional
               surface details. This is achieved by extruding the triangles
               of an existing mesh along their normals, and mapping a 3D
               function (e.g., a 3D texture) into the resulting prisms.
               Unfortunately, such a mapping is nonlinear. Previous
               approaches perform a piece-wise linear approximation by
               subdividing the prisms into tetrahedrons. However, such an
               approximation often leads to severe artifacts. In this paper
               we present a correct (i.e., smooth) mapping that does not
               rely on a decomposition into tetrahedrons. We present an
               efficient GPU ray casting algorithm which provides correct
               parallax, self-occlusion, and silhouettes, at the cost of
               longer rendering times. The new formulation also allows
               modeling shells with smooth curvatures using Coons patches
               within the prisms. Tangent continuity between adjacent
               prisms is guaranteed, while the mapping itself remains
               local, i.e. every curved prism content is modeled at runtime
               in the GPU without the need for any precomputation. This
               allows instantly replacing animated triangular meshes with
               prism-based shells.",
  pages =      "351--360",
  month =      6,
  organization = "Eurographics",
  booktitle =  "Rendering Techniques 2007 (Proceedings Eurographics
               Symposium on Rendering)",
  editor =     "Jan Kautz and Sumanta Pattanaik",
  isbn =       "978-3-905673-52-4",
  pages =      "10",
  publisher =  "Eurographics Association",
  location =   "Grenoble, France",
  keywords =   "Display algorithms, Shading",
  URL =        "http://www.cg.tuwien.ac.at/research/publications/2007/JESCHKE-2007-ISC/",
}