EVALUATION OF A REAL-TIME DIRECT VOLUME RENDERING SYSTEM

The results of evaluating VIRIM, that can be considered as the first r eal-time direct volume rendering system for ray-casting and volume ray -tracing, is described in this paper. Emphasis is]aid on experiences c oncerning the hardware architecture used with respect to the anticipat ed application area in medicine. The issues are the flexibility of VIR IM, the restriction to two gradient components only, the duplication o f the volume data sets on different modules, the size of the volume da ta set, the gray-value segmentation too], and the support of algorithm ic 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 r outines. Given this flexibility the application areas of real-time ren dering systems increase dramatically: most of the user requirements fo cus now not on visualization but on general volume data processing. Th e most serious bottleneck of VIRIM is the limited volume memory that i s 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 s imulation and control in head surgery. (C) 1997 Elsevier Science Ltd.