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Laboratoire d'InfoRmatique en Image et Systèmes d'information
UMR 5205 CNRS / INSA Lyon / Université Claude Bernard Lyon 1 / Université Lumière Lyon 2 / École Centrale de Lyon
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Research/technical report

Coherent Metropolis Light Transport with Multiple-Try Mutations [PDF]
Benjamin Segovia [LIRIS] , Jean-Claude Iehl [LIRIS] , Bernard Péroche [LIRIS]
Rapport de recherche RR-LIRIS-2007-015 , Soumis à Eurographics Symposium on Rendering 2007.


We present in this paper an effective way to implement coherent versions of Metropolis Light Transport ($MLT$) by using a class of Multiple-Try mutation strategies. Indeed, even if $MLT$ is an unconditionally robust rendering technique which can handle any kind of lighting configurations, it does not exploit any computation coherency. For example, it is difficult to cluster similar light rays into beams or cones, to perform $SIMD$ computations on vectorized data or to efficiently use geometry caching with non-tessellated scenes. To make Metropolis Light Transport suitable to most of the currently existing commercial renderers, we therefore propose to divide the algorithm into two parts: the first one explores the entire integration space in a way very similar to the initial implementation of Metropolis Light Transport while the second one "splits" in an unbiased way each sample into a family of arbitrarily coherent samples. We finally propose to illustrate the efficiency of our approach with an example of implementation of coherent ray tracing using $SIMD$ instructions.



  title         = {{Coherent Metropolis Light Transport with Multiple-Try 
  author        = {Benjamin {Segovia} and Jean-Claude {Iehl} and Bernard 
  year          = {2007},
  month         = apr,
  institution   = {LIRIS UMR 5205 CNRS/INSA de Lyon/Université Claude Bernard 
    Lyon 1/Université Lumière Lyon 2/École Centrale de Lyon},
  number        = {RR-LIRIS-2007-015},
   language      = {en},
  url           = {}