1 Achieving Direct Volume Visualization with Interactive Semantic Region Selection

Interactive direct visualization of 3D data requires fast update rates and the ability to extract regions of interest from the surrounding data. We have implemented MultiValued Classification volume renderers on a general purpose multiprocessor graphics platform (Pixel-Planes 5) that are faster than any yet reported (2 -15 frames per second). We have joined one of them with a sophisticated system for interactive semantic region selection, to our knowledge the first such combination. The result is a system that provides fast visualization of complex information in three dimensional data. Parallel volume rendering yields rates that make interactive control of image viewing possible for the first time. We have achieved rates as high as 15 frames per second by trading some function for speed, while volume rendering with a full complement of ramp classification capabilities is performed at 1.4 frames per second. These speeds have made the combination of region selection with volume rendering practical for the first time. Semantic driven selection, rather than geometric clipping, has proven to be a natural means of interacting with 3D data. Internal organs in medical data or other regions of interest can be built from preprocessed region primitives. We have applied the resulting combined system to real 3D medical data with encouraging results. The ideas presented are not just limited to our platform, but can be generalized to include most parallel architectures. We present lessons learned from writing fast volume renderers and applying of image processing techniques to viewing volumetric data.