Optimizing GPU Volume Rendering

Volume Rendering methods employing the GPU capabilities offer high performance on off-the-shelf hardware. In this article, we discuss the various bottlenecks found in the graphics hardware when performing GPU-based Volume Rendering. The specific properties of each bottleneck and the trade-offs between them are described. Further we present a novel strategy to balance the load on the identified bottlenecks, without compromising the image quality. Our strategy introduces a two-staged space-skipping, whereby the first stage applies bricking on a semi-regular grid, and the second stage uses octrees to reach a finer granularity. Additionally we apply early ray termination to the bricks. We demonstrate how the two stages address the individual bottlenecks, and how they can be tuned for a specific hardware pipeline. The described method takes into account that the rendered volume may exceed the available texture memory. Our approach further allows fast run-time changes of the transfer function.