GPU accelerated image aligned splatting

Abstract

Splatting is a popular technique for volume rendering, where voxels are represented by Gaussian kernels, whose pre-integrated footprints are accumulated to form the image. Splatting has been mainly used to render pre-shaded volumes, which can result in significant blurring in zoomed views. This can be avoided in the image-aligned splatting scheme, where one accumulates kernel slices into equi-distant, parallel sheet buffers, followed by classification, shading, and compositing. In this work, we attempt to evolve this algorithm to the next level: GPU (graphics processing unit) based acceleration. First we describe the challenges that the highly parallel "Gather" architecture of modern GPUs poses to the "Scatter" based nature of a splatting algorithm. We then describe a number of strategies that exploit newly introduced features of the latest-generation hardware to address these limitations. Two crucial operations to boost the performance in image-aligned splatting are the early elimination of hidden splats and the skipping of empty buffer-space. We describe mechanisms which take advantage of the early z-culling hardware facilities to accomplish both of these operations efficiently in hardware.