Ray Tracing with Sparse Boxes

Proceedings of Spring Conference on Computer Graphics, pp. 49-54, 2007
We present a new method for ray tracing acceleration by modification of current spatial data structures. We augment a spatial hierarchy such as kd-tree with sparsely distributed bounding boxes that are linked from bottom to top. The augmented data structures can be viewed as a hybrid between kd-trees and uniform grids. The augmentation by boxes is used in new traversal algorithms, which are not restricted to start the hierarchy traversal at the root node. This is in particular efficient for short rays where we significantly reduce the number of traversal steps through the hierarchy. Further we make use of ray coherence as well as explicit knowledge of ray distribution and initiate the traversal near the leaf nodes where the intersection is expected.