[OpenSCAD] Discuss manifoldness, co-incident faces edges etc

Doug Moen doug at moens.org
Tue Nov 12 22:17:07 EST 2019

nop head wrote:
> It would mean I could accidentally design non-printable object instead
> of being told it was non-manifold.

This has nothing to do with my original request.

What I want is better support for the 3MF file format.

The 3MF file format provides a legal, supported way to encode a model containing two cubes that touch along an edge, but OpenSCAD doesn't support this feature, in the way that 3MF files are currently written. So I'd like the 3MF export code to be fixed, so that when I export such a model, it is written as a valid 3MF file.

I don't think that better 3MF export will interfere with nop head's ability to use OpenSCAD.

The other thing I'd like is better 3MF import, with the assurance that if a *valid* 3MF model is imported, then the topology of the model is preserved, so that when the model is presented to CGAL for boolean operations, I don't get errors. Right now, during 3MF import, the model is converted to a PolySet, which is polygon soup. The topology information is discarded, and that's needed to convert the model to a Nef Polyhedron that CGAL can perform boolean operations on without reporting an error.

I don't think that better 3MF import will interfere with nop head's ability to use OpenSCAD.

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