Global Ray-bundle Tracing

László Szirmay-Kalos
Global Ray-bundle Tracing
TR-186-2-98-18, July 1998 [paper]

Information

Abstract

The paper presents a single-pass, view-dependent method to solve th e general rendering equation, using a combined finite element and random walk approach. Applying finite element techniques, the surfaces are decomposed into planar patches on which the radiance is assumed to be combined from finite number of unknown directional radiance functions by predefined positional basis functions. The directional radiance functions are then computed by random walk or by stochastic iteration using bundles of parallel rays. To compute the radiance transfer in a single direction, several global visibility methods are considered, including the global versions of the painter's, z-buffer, Weiler-Atherton's and planar graph based algorithms. The method requires no preprocessing except for handling point lightsources, for which a first-shot technique is proposed. The new method is particularly efficient for scenes including not very specular materials illuminated by large area lightsources or sky-light. In order to increase the speed for difficult lighting situations, walks can be selected according to their importance. The importance can be explored adaptively by the Metropolis and VEGAS sampling techniques.

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BibTeX

@techreport{Szir-1998-Glo,
  title =      "Global Ray-bundle Tracing",
  author =     "L\'{a}szl\'{o} Szirmay-Kalos",
  year =       "1998",
  abstract =   "The paper presents a single-pass, view-dependent method to
               solve th e general rendering equation, using a combined
               finite element and random walk approach. Applying finite
               element techniques, the surfaces are decomposed into planar
               patches on which the radiance is assumed to be combined from
               finite number of unknown directional radiance functions by
               predefined positional basis functions. The directional
               radiance functions are then computed by random walk or by
               stochastic iteration using bundles of parallel rays. To
               compute the radiance transfer in a single direction, several
               global visibility methods are considered, including the
               global versions of the painter's, z-buffer,
               Weiler-Atherton's and planar graph based algorithms. The
               method requires no preprocessing except for handling point
               lightsources, for which a first-shot technique is proposed.
               The new method is particularly efficient for scenes
               including not very specular materials illuminated by large
               area lightsources or sky-light. In order to increase the
               speed for difficult lighting situations, walks can be
               selected according to their importance. The importance can
               be explored adaptively by the Metropolis and VEGAS sampling
               techniques.",
  month =      jul,
  number =     "TR-186-2-98-18",
  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 =   "z-buffer, Metropolis method, importance sampling, stochastic
               iteration, Monte-Carlo and quasi-Monte Carlo integr, global
               radiance, Rendering equation",
  URL =        "https://www.cg.tuwien.ac.at/research/publications/1998/Szir-1998-Glo/",
}