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Practical product importance sampling for direct illumination

  • Roberto Scopigno
  • Eduard Gröller
Publiceringsår: 2008
Språk: Engelska
Sidor: 681-690
Publikation/Tidskrift/Serie: Computer Graphics Forum
Volym: 27
Nummer: 2
Dokumenttyp: Konferensbidrag
Förlag: Wiley-Blackwell


We present a practical algorithm for sampling the product of environment map lighting and surface reflectance.

Our method builds on wavelet-based importance sampling, but has a number of important advantages over previous methods. Most importantly, we avoid using precomputed reflectance functions by sampling the BRDF on-the-fly. Hence, all types of materials can be handled, including anisotropic and spatially varying BRDFs, as well

as procedural shaders. This also opens up for using very high resolution, uncompressed, environment maps. Our

results show that this gives a significant reduction of variance compared to using lower resolution approximations. In addition, we study the wavelet product, and present a faster algorithm geared for sampling purposes.

For our application, the computations are reduced to a simple quadtree-based multiplication. We build the BRDF

approximation and evaluate the product in a single tree traversal, which makes the algorithm both faster and more

flexible than previous methods.


  • Computer Science
  • Ray tracing
  • Photo-realistic rendering
  • Computer graphics
  • Importance sampling


Eurographics 2008
  • Computer Graphics-lup-obsolete
  • ISSN: 0167-7055
  • ISSN: 1467-8659

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