[OpenSCAD] degenerate polyhedron faces ok?

nop head nop.head at gmail.com
Tue Nov 19 07:03:40 EST 2019


Possibly because simple degenerate triangles get removed but ones where the
sum of two sides equals the third and ones where two sides are equal and
the third is zero don't get removed.

I made a branch where I removed all the degenerate triangles but decided it
was pointless without also removing self intersections because both are
consequences of truncating coordinates and grid snapping.

On Tue, 19 Nov 2019 at 11:01, adrianv <avm4 at cornell.edu> wrote:

> Nope.  Adding more geometry doesn't cause render to fail.
>
>
> nophead wrote
> > I think CGAL will throw an exception if you do a union with a unit
> cube();
> >
> > On Tue, 19 Nov 2019 at 01:27, Doug Moen <
>
> > doug@
>
> > > wrote:
> >
> >> Degenerate faces like this should generally be avoided. The face has
> zero
> >> area, and the normal vector is [0,0,0]. That's considered defective, and
> >> some programs will not allow you to import such a mesh. Other programs
> >> won't have a problem.
> >>
> >> On Mon, Nov 18, 2019, at 8:24 PM, adrianv wrote:
> >> > Is it legal to give a polyhedron faces that have zero area, e.g. a
> face
> >> like
> >> > [ [0,0,0],[0,0,0], [0,0,1],[0,0,1]]?  Or a degenerate "triangle" like
> >> > [[0,0,0],[0,0,0],[0,0,1]]?   What about a completely degenerate faces
> >> where
> >> > all vertices are equal?
> >> >
> >> > In trying to implement a certain degenerate case in my code I have
> used
> >> some
> >> > degenerate faces and it appears to work.  (I can render, and add
> >> multiple
> >> > polyhedra to the model.)   But I wonder if there might be hidden
> >> problems.
> >> >
> >> >
> >> >
> >> >
> >> > --
> >> > Sent from: http://forum.openscad.org/
> >> >
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