Photon Parameterisation for Robust Relaxation Constraints

Ben Spencer and Mark W. Jones

Presented at Eurographics 2013 in Girona, Spain

Winner of the
Günther Enderle Award for Best Paper

Image selected as winner of the
2013 Computer Graphics Forum Cover Competition


This paper presents a novel approach to detecting and preserving fine illumination structure within photon maps. Data derived from each photon’s primal trajectory is encoded and used to build a high-dimensional kd-tree. Incorporation of these new parameters allows for precise differentiation between intersecting ray envelopes, thus minimizing detail degradation when combined with photon relaxation. We demonstrate how parameter-aware querying is beneficial in both detecting and removing noise. We also propose a more robust structure descriptor based on principal components analysis that better identifies anisotropic detail at the sub-kernel level.We illustrate the effectiveness of our approach in several example scenes and show significant improvements when rendering complex caustics compared to previous methods.


Source materials

PDF (pre-print; ~12MB)
Video (H264 MP4; ~55MB)
• Supplementary material
(available soon)
• BibTex (available soon)

Useful links

Eurographics 2013 homepage
Computer Graphics Forum homepage
Into The Blue: Better Caustics using Photon Relaxation
Swansea University Computer Science