Accelerating Volume Raycasting using Occlusion Frustums

Abstract

GPU-based volume raycasting allows to produce high quality renderings on current graphics hardware. The use of such raycasters is on the rise due to their inherent flexibility as well as the advances in hardware performance and functionality. Although recent raycasting systems achieve interactive frame rates on high-end graphics hardware, further improved performance would enable more complex rendering techniques, e. g., advanced illumination models. In this paper we introduce a novel approach to empty space leaping in order to reduce the number of costly volume texture fetches during ray traversal. We generate an optimized proxy geometry for raycasting which is based on occlusion frustums obtained from previous frames. Our technique does not rely on any preprocessing, introduces no image artifacts, and in contrast to previous point-based methods works also for non-continuous view changes. Besides the technical realization and the performance results, we also discuss the potential problems of ray coherence in relation to our approach and restrictions in current GPU architectures. The presented technique has been implemented using fragment and geometry shaders and can be integrated easily into existing raycasting systems.