nataraja@hplabs.hpl.hp.com (Balas Natarajan) (05/01/91)
in regard to marching cubes and holes; there are two possible methods of fixing the holes. method (1): use an ad hoc but consistent treatment of the ambiguities. this eliminates the holes, but can result in topologies that are different from the topology of the true isosurface of the trilinear interpolant of the data. an unfortunate side effect of the latter is that refining the data can cause drastic changes in topology. method (2): analyze the true topology of the isosurface of the trilinear interpolant and report this topology. this eliminates the holes, and the refinement problem. the challenge here is to still report a small number of polygons for each voxel, unlike the method of "dividing cubes"; i have implementations of both methods. in method (1) i use a slight and "greedy" modification of the marching cubes case table. method (2) involves a topological analysis of the trilinear interpolant in each voxel. my implementation of method (2) runs about 10% slower than marching cubes on the sample data i checked it on. --bkn ~ ~