A VOLUME VISUALIZATION ALGORITHM USING A COHERENT EXTENDED WEIGHT MATRIX

Direct cell-to-cell volume visualization algorithms, also called proje ctive rendering methods, present the advantage of allowing semi-transp arencies and, additionally, as they project all the samples, they avoi d the voxel-space aliasing. However, they are generally computationall y expensive and artifacts may appear in the projection. In this paper, different projective strategies-are reviewed and compared. A new algo rithm, based on a back-to-front (BTF) voxel-to-voxel traversal, is pro posed. It consists of the computation, in a preprocess, of 16 Extended Generalized Weight (EGW) matrices, based on the voxel's geometry and the viewpoint direction. Taking into advantage the voxel-to-voxel cohe rence, the EGW are applied incrementally to each voxel as footprints t o be composited with the image buffer, according to the voxel shade an d opacity values. It is shown that the method avoids artifacts, and th at it has a low computational cost because it does not require re-voxe llization and it does not perform any geometric computation in the pro jection process. It is specially suitable for voxel representations an d image space resolutions such that the projection of a single voxel c overs more than one pixel.