GPU-based direct volume rendering with advanced illumination and Deep Attenuation Shadows

This paper presents a novel framework which implements GPU-based single pass raycasting with high quality shadows and advanced illumination by using sobel gradients on-the-fly on current graphics hardware. The algorithm has changed traditional gradient and illumination process of GPU-based raycasting, which used to estimate gradient of every voxel in CPU and translate it to GPU through 3D texture. We introduce deep attenuation shadows (DAS), a new technique that produces fast and high quality shadows for GPU-based single pass raycasting. DAS does not produce intermediate data structure; nor does it depend on complex geometry computations or additional textures look up. We also exploit early ray termination and terminate null ray to reduce computation cost of fragment to obtain interactive performance speed. Based on these techniques, our implementation shows a promising performance while producing images of advanced illumination and high quality shadows than traditional GPU-based raycasting.