Re: files on open/closed cell strucrus

From: George W. Hart <>
Date: Wed Jan 21 2004 - 19:45:15 EET

Bo Atkinson wrote:
> ...It might be of interest that formZ, (with the latest version 4.x and
> latest pc hardware), was able to Boolean 343 soccer balls very easily.
> ... Yet to be fair, more
> experimentation is deserved before saying exactly where the limit is...

Computing Boolean operations on objects defined by their surface
boundary can be "easy" or "hard" depending on how the faces and edges
intersect each other. Simpler algorithms have problems if some planes,
edges, or vertices are very close to coincident. In your model, it
appears that you made a regular 7x7x7 lattice of identical balls, so the
intersection geometry was the same in each case. That is fundamentally
no harder a test than the union of 27 balls in a 3x3x3 lattice---it just
repeats this same question many times.

For a better test, you could rotate each ball a random amount, scale it
slightly differently, and perturb its position a small random distance.
Then each intersection will be a slightly different problem for the
software to solve. In that case, I suspect there is a good chance that
at least one of them will expose a software problem. (But I would be
happy to hear otherwise...)

Received on Wed Jan 21 19:23:24 2004

This archive was generated by hypermail 2.1.8 : Tue Jan 12 2010 - 19:37:11 EET