INTERACTIVE VOLUME NAVIGATION

Volume navigation is the interactive exploration of volume data sets b y ''flying'' the viewpoint through the data; producing a volume render ed view at each frame. We present an inexpensive perspective volume na vigation method designed to be run on a PC platform with accelerated 3 D graphics hardware. The heart of the method is a two phase perspectiv e raycasting algorithm that takes advantage of the coherence inherent in adjacent frames during navigation. The algorithm generates a sequen ce of approximate volume-rendered views in a fraction of the time that would be required to compute them individually. The algorithm handles arbitrarily large volumes by dynamically swapping data within the cur rent view frustum into main memory as the viewpoint moves through the volume. We also describe an interactive volume navigation application based on this algorithm. The application renders gray-scale, RGB, and labeled RGB volumes by volumetric compositing, allows trilinear interp olation of sample points, and implements progressive refinement during pauses in user input.