Fast Volumetric Gradient Shading Approximations for Scientific Ray Tracing
Carson Brownlee, David E DeMarle · Apress eBooks · 2021
In scientific visualization, direct volume rendering requirements range from fast approximations for interactive data exploration to photorealism with physically based shading for renderings destined for the general public. Gradient shaded lighting is a common non-physically based shading method used in scientific volume visualization that increases the level of realism and helps distinguish features in the data over simple forward ray marching. Gradient shading comes at a significant runtime cost over simple ray casting, especially as secondary rays are calculated at each sample point for lighting effects such as shadows and ambient occlusion. In this chapter we examine the simple optimization of shading at the single point of highest contribution. In practice this method gives most of the benefits of full gradient shading that help in feature detection and realism, with an order of magnitude performance improvement.