[OpenSCAD] Discuss Digest, Vol 38, Issue 22

doug moen doug at moens.org
Tue Jan 23 13:17:48 EST 2018


This idea has been discussed before. The CGAL "Alpha Shapes" module is one
way to implement this. Note that we already use CGAL for boolean operations
like union.

https://doc.cgal.org/latest/Alpha_shapes_3/index.html

On 23 January 2018 at 13:09, jim.klessig <jim.klessig at gmail.com> wrote:

> "Actually it is possible, but probably not inside OpenSCAD.  Many years
> ago I
> was in the land surveying business and I wrote a routine to take randomly
> spaced 3D points"
>
> I would disagree.  Your routine would be making some (probably un stated)
> assumptions  about the shape. Such as that the points do not form a "cave",
> and probably what points represent a boundary.
>
> For example how would your routine deal with the example I gave,  of 8
> points representing the corners of a cube.
> There are multiple "correct" representations of that set of points.
>
> I would suspect that your routine would assume those points are either a
> cube shaped bump in a flat plane, or a cubical hole in an otherwise flat
> plane.  Both of which are making perfectly reasonable assumptions for
> making it topographical map.
> But those assumptions would be/could be  incorrect for just that set of 8
> points, "floating in space" with no other information.
> Essentially there are too many degrees of freedom for the problem to be
> solvable as he posed it.
>
> Sent from my U.S. Cellular® Smartphone
>
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