Double Hierarchies for Directional Importance Sampling in Monte Carlo Rendering

Norbert Bus and Tamy Boubekeur
Journal of Computer Graphics Techniques, to appear



We propose a novel representation of the light field tailored to improve importance sampling for Monte Carlo rendering. The domain of the light field i.e., the product space of spatial positions and directions is hierarchically subdivided into subsets on which local models characterize the light transport. The data structure is based on double trees, and only approximates the exact light field, but enables efficient queries for importance sampling and easy setup by tracing photons in the scene. The framework is simple yet flexible, supports any type of local model for representing the light field, provided it can be efficiently importance sampled, and progressive refinement with an arbitrary number of photons. Last, we provide a reference open source implementation of our method.


Related Publication

An early version of this work is presented at the ACM SIGGRAPH 2017 talk program under the title Double Hierarchies for Efficient Sampling in Monte Carlo Rendering. Please reference the full JCGT paper whenever relevant (e.g., citations in papers, use of the source code)


  author =       {Norbert Bus and Tamy Boubekeur},
  title =        {Double Hierarchies for Directional Importance Sampling in Monte Carlo Rendering},
  year =         2017,
  month =        {August},
  day =          28,
  journal =      {Journal of Computer Graphics Techniques (JCGT)},
  volume =       6,
  number =       3,
  pages =        {25--37},
  url =          {},
  issn =         {2331-7418}