Importance Sampling with Hemispherical Particle Footprints

Information

  • Publication Type: Technical Report
  • Workgroup(s)/Project(s): not specified
  • Date: January 2001
  • Number: TR-186-2-01-05
  • Keywords: importance map, photon map, particle map, importance sampling

Abstract

We present a new importance sampling technique for stochastic ray-based global illumination methods. It allows to enhance the efficiency of global illumination calculations in general scenes with complex illumination settings by selecting preferably those sampling or shooting directions which yield a high contribution. The probability density functions for this are generated with a photon map or importance map that represents the expected contribution. A direction for a given point in the scene is selected by making directional footprints of the nearest neighbor particles onto the hemisphere of the point. By selecting the radii of the footprints adaptively according to the directional density of the particles, rays can be shot precisely into highly contributing regions where several particles come from in a small solid angle. We compare our new technique with existing particle map based importance sampling and show that our new technique achieves a considerably lower level of noise and spots in the same computation time.

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BibTeX

@techreport{Hey-2001-ImpX,
  title =      "Importance Sampling with Hemispherical Particle Footprints",
  author =     "Heinrich Hey and Werner Purgathofer",
  year =       "2001",
  abstract =   "We present a new importance sampling technique for
               stochastic ray-based global illumination methods. It allows
               to enhance the efficiency of global illumination
               calculations in general scenes with complex illumination
               settings by selecting preferably those sampling or shooting
               directions which yield a high contribution. The probability
               density functions for this are generated with a photon map
               or importance map that represents the expected contribution.
               A direction for a given point in the scene is selected by
               making directional footprints of the nearest neighbor
               particles onto the hemisphere of the point. By selecting the
               radii of the footprints adaptively according to the
               directional density of the particles, rays can be shot
               precisely into highly contributing regions where several
               particles come from in a small solid angle. We compare our
               new technique with existing particle map based importance
               sampling and show that our new technique achieves a
               considerably lower level of noise and spots in the same
               computation time.",
  month =      jan,
  number =     "TR-186-2-01-05",
  address =    "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria",
  institution = "Institute of Computer Graphics and Algorithms, Vienna
               University of Technology ",
  note =       "human contact: technical-report@cg.tuwien.ac.at",
  keywords =   "importance map, photon map, particle map, importance
               sampling",
  URL =        "/research/publications/2001/Hey-2001-ImpX/",
}