Authors: 
Min Shih, Yubo Zhang, Kwan-Liu Ma
Abstract: 
The benefits of using advanced illumination models in volume vi- sualization have been demonstrated by many researchers. Interac- tive volume rendering incorporated with advanced lighting has been achieved with GPU acceleration for regular-grid volume data, mak- ing volume visualization even more appealing as a tool for 3D data exploration. This paper presents an interactive illumination strat- egy, which is specially designed and optimized for volume visual- ization of unstructured-grid data. The basis of the design is a par- tial differential equation based illumination model to simulate the light propagation, absorption, and scattering within the volumetric medium. In particular, a two-level scheme is introduced to over- come the challenges presented by unstructured grids. Test results show that the added illumination effects such as global shadowing and multiple scattering not only lead to more visually pleasing visu- alization, but also greatly enhance the perception of the depth infor- mation and complex spatial relationships for features of interest in the volume data. This volume visualization enhancement is intro- duced at a time when unstructured grids are becoming increasingly popular for a variety of scientific simulation applications.