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Item CHC+RT: Coherent Hierarchical Culling for Ray Tracing(The Eurographics Association and John Wiley & Sons Ltd., 2015) Mattausch, Oliver; Bittner, Jirí; Jaspe, Alberto; Gobbetti, Enrico; Wimmer, Michael; Pajarola, Renato; Olga Sorkine-Hornung and Michael WimmerWe propose a new technique for in-core and out-of-core GPU ray tracing using a generalization of hierarchical occlusion culling in the style of the CHC++ method. Our method exploits the rasterization pipeline and hardware occlusion queries in order to create coherent batches of work for localized shader-based ray tracing kernels. By combining hierarchies in both ray space and object space, the method is able to share intermediate traversal results among multiple rays. We exploit temporal coherence among similar ray sets between frames and also within the given frame. A suitable management of the current visibility state makes it possible to benefit from occlusion culling for less coherent ray types like diffuse reflections. Since large scenes are still a challenge for modern GPU ray tracers, our method is most useful for scenes with medium to high complexity, especially since our method inherently supports ray tracing highly complex scenes that do not fit in GPU memory. For in-core scenes our method is comparable to CUDA ray tracing and performs up to 5:94 better than pure shader-based ray tracing.Item T-SAH: Animation Optimized Bounding Volume Hierarchies(The Eurographics Association and John Wiley & Sons Ltd., 2015) Bittner, Jirí; Meister, Daniel; Olga Sorkine-Hornung and Michael WimmerWe propose a method for creating a bounding volume hierarchy (BVH) that is optimized for all frames of a given animated scene. The method is based on a novel extension of surface area heuristic to temporal domain (T-SAH). We perform iterative BVH optimization using T-SAH and create a single BVH accounting for scene geometry distribution at different frames of the animation. Having a single optimized BVH for the whole animation makes our method extremely easy to integrate to any application using BVHs, limiting the per-frame overhead only to refitting the bounding volumes.We evaluated the T-SAH optimized BVHs in the scope of real-time GPU ray tracing. We demonstrate, that our method can handle even highly complex inputs with large deformations and significant topology changes. The results show, that in a vast majority of tested scenes our method provides significantly better run-time performance than traditional SAH and also better performance than GPU based per-frame BVH rebuild.