Real-time illumination for two-level volume rendering

Abstract

We propose improvements to real-time two-level rendering incorporating ray cast shadows and ambient occlusion of 3D volumetric datasets. Our ambient occlusion calculation utilises the same sampling scheme as standard per-voxel Phong shading thus allowing for an extremely computationally efficient rendering in comparison to other ambient occlusion algorithms. Our ray cast shadows technique requires no pre-processing, does not significantly increase memory requirements and is compatible with ray cast volume renderers. We validate these techniques through a number of user experiments. The results indicate that our ambient occlusion method increases the visual information in an image. Meanwhile, ray cast shadows appear to not provide the hypothesised improvement to image understanding, however this raises some interesting implications regarding the practical relevance of shadows in such two-level volume renderings. © 2012 Springer-Verlag.