I'm trying the program qhull from www.qhull.org, and it gives me these options when I run it: Output options (subset): s - summary of results (default) i - vertices incident to each facet n - normals with offsets p - vertex coordinates (if 'Qc', includes coplanar points) if 'v', Voronoi vertices Fp - halfspace intersections Fx - extreme points (convex hull vertices) FA - compute total area and volume o - OFF format (if 'v', outputs Voronoi regions) G - Geomview output (2-d, 3-d and 4-d) m - Mathematica output (2-d and 3-d) QVn - print facets that include point n, -n if not TO file- output results to file, may be enclosed in single quotes What are normals with offsets? When I use this option, it gives me 4 numbers instead of 3. I thought maybe the 4th was the distance from 0 for the center of the face or something like that. So, I thought I could ignore the 4th number, but things don't look right when I draw it using the first 3 numbers. Anyhow, if you know what normals with offsets are, please enlighten me. Mike http://www.coolgroups.com/