A Light Hierarchy for Fast Rendering of Scenes with Many Lights


Eric Paquette, Pierre Poulin, and George Drettakis
In Computer Graphics Forum (Proceedings of Eurographics '98)

Abstract

We introduce a new data structure in the form of a light hierarchy for efficiently ray-tracing scenes with many light sources. An octree is constructed with the point light sources in a scene. Each node represents all the light sources it contains by means of a virtual light source. We determine bounds on the error committed with this approximation to shade a point, both for the cases of diffuse and specular reflections. These bounds are then used to guide a hierarchical shading algorithm. If the current level of the light hierarchy provides shading of sufficient quality, the approximation is used, thus avoiding the cost of shading for all the light sources contained below this level. Otherwise the descent into the light hierarchy continues.

Our approach has been implemented for scenes without occlusion. The results show important acceleration compared to standard ray-tracing (up to 90 times faster) and an important improvement compared to Ward's adaptive shadow testing.

Keywords

Image synthesis, rendering, ray-tracing, hierarchy, illumination, reflection, Phong, bounds, clustering, octree.

BibTeX entry

@InProceedings{Paquette:1998:LHF,
  author =       "Eric Paquette and Pierre Poulin and George Drettakis",
  title =        "A Light Hierarchy for Fast Rendering of Scenes with 
                  Many Lights",
  editor =       {N. G\"obel and F. Nunes Ferreira (guest editor)},
  pages =        "63--74",
  booktitle =    "Computer Graphics Forum (Eurographics '98 Conference
                  Proceedings)",
  year =         "1998",
  organization = "Eurographics",
  month =        sep,
  note =         "held in Lisbon, Portugal, 02-04 September 1998",
}

Online version

Adobe PDF version of the paper.

Adobe PDF version of the presentation of the paper at the Eurographics '98 conference in Lisbon.

Additionnal Material

Page with graphics and brief description of the method.

Erratum

There is an error in the derivation of the specular bound in appendix A. The bound presented in section 4.3.1, the statistics and conclusions are all correct. It is only in the appendix that there is an error. The online version of the paper is correct but the version in the proceedings is incorrect. The correction of that error is available in the form of a PDF file (requires Acrobat Reader 3.0).



Last modified: Tue Feb 11 16:55:19 Eastern Standard Time 2003