[OpenSCAD] Unusual hull() and minkowski modelling

doug moen doug at moens.org
Sun Jun 19 20:50:23 EDT 2016


Ronaldo wrote: "Although mophing operator is appealing, singularities may
be raised by it
independent on how it is defined. Imagine what happens when morphing a solid
with disjoint parts with another one with just one part. Or morphing a torus
and a sphere. For some value of t, the morphing will be a non-manifold."

Sure morphing will produce singularities, but so will minkowski(),
difference() and union(). So morphing is nothing special.

A basic challenge with implementing CSG using a mesh representation is that
CSG operations are not closed over 2-manifold meshes. Even if the inputs
are 2-manifold, the outputs might not be, because singularities can be
introduced. The best way to handle with this is to make all of the CSG
operations tolerant of singularities. Our current implementation is
tolerant of singularities in a lot of common cases, and this has improved
over time.

On 19 June 2016 at 08:34, Ronaldo <rcmpersiano at gmail.com> wrote:

> doug.moen wrote
> > This stuff is really cool, Ronaldo.
> >
> > I was familiar with the morph() operation from other CSG systems, but I
> > just assumed it was impossible in OpenSCAD. So I'm impressed. I notice it
> > only works correctly if scale(0) returns a 0D point (as opposed to
> > returning nothing).
>
> Although mophing operator is appealing, singularities may be raised by it
> independent on how it is defined. Imagine what happens when morphing a
> solid
> with disjoint parts with another one with just one part. Or morphing a
> torus
> and a sphere. For some value of t, the morphing will be a non-manifold.
>
>
>
> --
> View this message in context:
> http://forum.openscad.org/Unusual-hull-and-minkowski-modelling-tp17730p17761.html
> Sent from the OpenSCAD mailing list archive at Nabble.com.
>
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