[OpenSCAD] Evaluating imported STL's

Ronaldo rcmpersiano at gmail.com
Thu Jun 16 12:16:39 EDT 2016


Rudolf,

You raised good points but I will keep mine about Minkowski. The example you
have shown of a vanishing cube is idiosyncratic but for other reasons. I
would expect that 

           scale(0) sphere;

to be a point, the origin, and not a void set.

In Mathematics, you have a non-void set by doing a Minkowski sum of a point
and a non-void set. I thought we have no way in OpenSCAD to do a Minkowski
sum of a set with only a point or a line segment or a 2D shape due to the
simple fact that we can't express such sets or mix 2D shapes with 3D shapes
in OpenSCAD operations. However, we can at least in Minkowski operations.

> minkowski() {
>      cube(1);
>      intersection() {
>         cube(1);
>         translate([$t-1,$t-1,$t-1]) cube(1);
>      }
> }

And that is not idiosyncratic. It does exactly what I would expect. The
intersection is not void, it is a square that shrinks to the origin when
$t=0. The scaled sphere should do the same.

BTW, the above "technique" may be very usefull for rounding only some edges
of a solid.

There is much more complexities behind the scene... :)



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