RAY CASTING AND THE ENCLOSING-NET ALGORITHM FOR EXTRACTING SHAPES FROM VOLUME DATA

One of the most useful applications of virtual reality is to let docto rs view the inside of the human body non-invasively and in real time. In this paper, we first survey the area of virtual reality and volume- visualization techniques. We discuss our ray casting implementation fo r viewing the medical data which is available as a set of slices from NMR and CT scans. Next we present a new method, the enclosing-net algo rithm, for extracting iso-surfaces from volume data. A simple implemen tation of our technique is described. Since the topology of the extrac ted surface is well defined and non-ambiguous, the enclosing-net algor ithm eliminates a major problem of surface extraction techniques. In a ddition, the number of polygons representing the surface can be contro lled to obtain a finer shape. Therefore real-time interaction is feasi ble on both low-end and high-end graphics machines, making the enclosi ng-net algorithm suitable for virtual reality experiments.