Abstract

The results of evaluating VIRIM, that can be considered as the first real-time direct volume rendering system for ray-casting and volume ray-tracing, is described in this paper. Emphasis is laid on experiences concerning the hardware architecture used with respect to the anticipated application area in medicine. The issues are the flexibility of VIRIM, the restriction to two gradient components only, the duplication of the volume data sets on different modules, the size of the volume data set, the gray-value segmentation tool, and the support of algorithmic improvements like space-leaping, early ray-termination and others. It turned out that flexibility gives the main benefits since it allows easy response to different demands during integration into clinical routines. Given this flexibility the application areas of real-time rendering systems increase dramatically: most of the user requirements focus now not on visualization but on general volume data processing. The most serious bottleneck of VIRIM is the limited volume memory that is integrated in the first prototype. The gray-value segmentation tool turned out to be very valuable. It is highly useful if original, i.e. unsegmented data have to be dealt with, and if pre-segmented data have to be investigated. All other benefits and architectural shortcomings are not critical for the application areas of VIRIM, i.e. operation simulation and control in head surgery.

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