Incoming First-Shot for Non-Diffuse Global Illumination

László Szirmay-Kalos, Mateu Sbert, Roel Martinez, Robert F. Tobler
Incoming First-Shot for Non-Diffuse Global Illumination
TR-186-2-00-04, April 2000 [paper]

Information

Abstract

This paper presents a method that can replace the small and medium size lightsources by their effect in non-diffuse global illumination algorithms. Incoming first-shot is a generalization of a preprocessing technique called the first-shot that was developed for speeding up global diffuse radiosity algorithms. Alternatively, it can also be approached as a generalization of the direct-lightsource computation involved in gathering type methods. In order to reduce the prohibitive memory requirements of the original first-shot when it is applied to non-diffuse scenes in a direct manner, the proposed new method computes and stores only the incoming radiance generated by the lightsources and the reflected radiance is obtained from the incoming radiance on the fly taking into account the local BRDF. Since the radiance function of the reflection is smoother and flatter than the original lightsource function, this replacement makes the integrand of the rendering equation have significantly smaller variation, which can speed up global illumination algorithms. The paper also discusses how the first-shot technique can be built into a stochastic iteration algorithm using ray-bundles, and provides run-time statistics.

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BibTeX

@techreport{Szirmay-2000-NDFS,
  title =      "Incoming First-Shot for Non-Diffuse Global Illumination",
  author =     "L\'{a}szl\'{o} Szirmay-Kalos and Mateu Sbert and Roel
               Martinez and Robert F. Tobler",
  year =       "2000",
  abstract =   "This paper presents a method that can replace the small and
               medium size lightsources by their effect in non-diffuse
               global illumination algorithms. Incoming first-shot is a
               generalization of a preprocessing technique called the
               first-shot that was developed for speeding up global diffuse
               radiosity algorithms. Alternatively, it can also be
               approached as a generalization of the direct-lightsource
               computation involved in gathering type methods. In order to
               reduce the prohibitive memory requirements of the original
               first-shot when it is applied to non-diffuse scenes in a
               direct manner, the proposed new method computes and stores
               only the incoming radiance generated by the lightsources and
               the reflected radiance is obtained from the incoming
               radiance on the fly taking into account the local BRDF.
               Since the radiance function of the reflection is smoother
               and flatter than the original lightsource function, this
               replacement makes the integrand of the rendering equation
               have significantly smaller variation, which can speed up
               global illumination algorithms. The paper also discusses how
               the first-shot technique can be built into a stochastic
               iteration algorithm using ray-bundles,                   and
               provides run-time statistics.",
  month =      apr,
  number =     "TR-186-2-00-04",
  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 =   "first-shot, finite-element techniques, global methods,
               Monte-Carlo quadrature, stochastic iteration, Non-diffuse
               global illumination",
  URL =        "https://www.cg.tuwien.ac.at/research/publications/2000/Szirmay-2000-NDFS/",
}