Lightcuts: a scalable approach to illumination
ACM SIGGRAPH 2005 Papers
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Lightcuts is an efficient illumination method for scenes with many complex lights, by hierarchical clustering of lights in a light tree. However, when the light tree is large, it is very time-consuming to traverse in the tree to get the suitable clusters of lights for illumination computation. For this, some methods proposed to use image coherence for neighboring pixels to share clusters of lights, and so save traversal cost in the light tree. However, with the image resolutions reduced, fewer and fewer coherences could be used and so their acceleration efficiency will be reduced dramatically, and they may even decrease the rendering efficiency. This sketch proposes to exploit spatial coherences to enhance rendering by lightcuts. For the intersection points between rays and the scene, they are clustered on the fly and the points of a cluster search their respective suitable clusters of lights from a common set of clusters, called a common cut. In this way, the traversal cost from the tree root to the common cuts can be considerably saved for acceleration. Results show that our method can be faster than the methods using image coherence, and works stably with various image resolutions. And with the lights being more complex, our method can obtain more acceleration.