Progressive Photon Relaxation

Ben Spencer and Mark W. Jones

ACM Transactions on Graphics. 32(1), January 2013.

Update: due to time constraints, we regret that we are unable to present this paper at SIGGRAPH 2013. Please check back soon for updates.


We introduce a novel algorithm for progressively removing noise from view-independent photon maps while simultaneously minimizing residual bias. Our method refines a primal set of photons using data from multiple successive passes to estimate the incident flux local to each photon. We show how this information can be used to guide a relaxation step with the goal of enforcing a constant, per-photon flux. Using a reformulation of the radiance estimate, we demonstrate how the resulting blue noise photon distribution yields a radiance reconstruction in which error is significantly reduced. Our approach has an open-ended runtime of the same order as unbiased and asymptotically consistent rendering methods, converging over time to a stable result. We demonstrate its effectiveness at storing caustic illumination within a view-independent framework and at a fidelity visually comparable to reference images rendered using progressive photon mapping.



Source materials

Pre-print (PDF; ~12MB)
Video (H264 MP4; ~55MB)
Supplementary material (PDF; ~1.6MB)
Entry on ACM digital library


    author = {Spencer, Ben and Jones, Mark W.},
    title = {Progressive photon relaxation},
    journal = {ACM Trans. Graph.},
    issue_date = {January 2013},
    volume = {32},
    number = {1},
    year = {2013},
    pages = {7:1--7:11},
    articleno = {7},
    publisher = {ACM},
    address = {New York, NY, USA},

Useful links

ACM Transactions on Graphics homepage
SIGGRAPH 2013 homepage
Swansea University Computer Science