VIZARD - Visualization Accelerator for Realtime Display

Abstract

Volume rendering has traditionally been an application for supercomputers, workstation networks or expensive special-purpose hardware. In contrast, this report shows how far we have reached using the other extreme: the low-end PC platform. We have alleviated the mismatch between this demanding application and the limited computational resources of a PC in three ways: several stages in the visualization pipeline are placed into a preprocessing step, the volume rendering algorithm was optimized using a special data compression scheme, and the algorithm has been implemented in hardware as a PCI-compatible coprocessor (lXZ,4RD). These methods give us a frame rate of up to 1OHz for 256 <sup>3</sup> data sets and an acceptable image quality, although the accelerator prototype was built using relatively slow FPGA-technology. In a low-cost environment a coprocessor must not be more expensive than the host itself, and so VIZARD was designed to be manufacturable for a few hundred dollars. The special data compression scheme allows the data set to be placed into the main memory of the PC and eliminates the need for an expensive, separate volume memory. The entire visualization system consists of a portable PC with two built-in accelerator boards. Despite its small size, the system provides perspective raycasting for realtime walk-throughs. Additional features include stereoscopic viewing using shutter glasses and volume animation.