[OpenSCAD] Fwd: Getting two volumes

Clifford Wolf clifford at clifford.at
Sat Dec 5 09:26:52 CET 2009


On Sat, Dec 05, 2009 at 02:12:06AM +0000, Nuno Cruz wrote:
> So I have this code and I was thinking that I would just output one
> volume, so the I could export it to STL, but instead it's coming with
> two volumes.
> Can someone help me?

your problem is not the number of volumes. a design with two volumes
contains one object. the volumes are the inside of the object and the
outside space.

you problem is that your object is not a valid 2-manifold. here is a little
example demonstrating what goes wrong with your design:

	module example1() {
		cube([20, 20, 20]);
		translate([-20, -20, 0]) cube([20, 20, 20]);
		cube([50, 50, 5], center = true);

	module example2() {
		cube([20.1, 20.1, 20]);
		translate([-20, -20, 0]) cube([20.1, 20.1, 20]);
		cube([50, 50, 5], center = true);

the example1 module is not a valid 2-manifold because both cubes are
charing one edge. they touch each other but do not intersect. example2
is a valid 2-manifold because there is an intersection. now the 'each edge
must connect exactly two facets' constraints of 2-manifolds is is met.

 - clifford

"Paranoia is faith in a hidden order behind the visible."
 - pi, the movie

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