[OpenSCAD] GROUP vs UNION

[Triffid Hunter]

On Wed, Feb 8, 2012 at 11:13 AM, Alan Cox <alan at lxorguk.ukuu.org.uk> wrote:

> On Tue, 7 Feb 2012 23:57:38 +0000
> nop head <nop.head at gmail.com> wrote:
>
> > Are overlapping shells allowed in an STL? Surely that is one of the
> > non-manifold things that upsets slicers.
>
> 3D printers might not like it but I don't see why STL doesn't allow it


STL will allow anything, it's simply a list of triangles in 3d space.

That's one of the troubles our slicers have, there's no requirement for
manifoldness.

I'm also curious as to what possible use you could have for deliberately
creating a self-intersecting non-manifold object?
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