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Abstract

We describe a novel data structure for representing light transport called ray
map. The ray map extends the concept of photon maps: it stores not only photon
impacts but the whole photon paths. We demonstrate the utility of ray maps for
global illumination by eliminating boundary bias and reducing topological bias
of density estimation in global illumination. Thanks to the elimination of
boundary bias we could use ray maps for fast direct visualization with the
image quality being close to that obtained by the expensive final gathering
step. We describe in detail our implementation of the ray map using a lazily
constructed kD-tree. We also present several optimizations bringing the ray map
query performance close to the performance of the photon map.