Volume navigation is the interactive exploration of volume data sets by "flying" the view point through the data, producing a volume rendered view at each frame. In this paper, we present an inexpensive perspective volume navigation method designed to run on a PC platform with acceIerated 3D graphics hardware. We compute perspective projections at each frame, allow trilinear interpolation of sample points, and render both gray scale and RGB volumes by volumetric compositing. Our implementation

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... andles arbitrarily large volumes, by dynamically swapping data within the local depth-limited frustum into main memory as the viewpoint moves through the volume. We descrl!e a new ray casting algorithm that takes advantage of the coherence inher&t in adjacent frames to generate a sequenie of izpproximte animated frames much faster than they could be computed individually. We also take advantage of the 3D graphics accelemtion hardware to offload much of the alpha blending and resampling from the CPU.