Caustic Forecasting: Unbiased Estimation of Caustic Lighting for Global Illumination

• Published in: Computer graphics forum Vol. 27; no. 7; pp. 1963 - 1970
• Main Authors: Budge, B. C., Anderson, J. C., Joy, K. I.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01-10-2008
• Subjects: I.3.6 [Computer Graphics]: Methodology and Techniques; I.3.7 [Computer Graphics]: Three-Dimensional Graphics and Realism; Lighting; Spatial data
• ISSN: 0167-7055; 1467-8659
• DOI: 10.1111/j.1467-8659.2008.01345.x

We present an unbiased method for generating caustic lighting using importance sampled Path Tracing with Caustic Forecasting. Our technique is part of a straightforward rendering scheme which extends the Illumination by Weak Singularities method to allow for fully unbiased global illumination with rapid convergence. A photon shooting preprocess, similar to that used in Photon Mapping, generates photons that interact with specular geometry. These photons are then clustered, effectively dividing the scene into regions which will contribute similar amounts of caustic lighting to the image. Finally, the photons are stored into spatial data structures associated with each cluster, and the clusters themselves are organized into a spatial data structure for fast searching. During rendering we use clusters to decide the caustic energy importance of a region, and use the local photons to aid in importance sampling, effectively reducing the number of samples required to capture caustic lighting.