[OpenSCAD] Unusual hull() and minkowski modelling

Parkinbot rudolf at parkinbot.com
Fri Jun 17 11:02:08 EDT 2016


Ronaldo, 

there are people shuffling eggs with wheel loaders ... ;-) 
Others find themselves using  Mathematica
<https://de.wikipedia.org/wiki/Mathematica>   sooner or later.

For a Mathematician it can be fun to study this degenerate stuff, and it can
indeed discover some crash scenarios in OpenSCAD. 
But to be honest, I don't see any practical use in working with pathological
constructs, beyond curiosity. Implementation will change over time, and any
of this code might be broken sooner or later. 

Again, F5 uses your graphics system for rendering. OpenSCAD 'calculates' its
stuff by feeding proper representations into subsystems, which are supposed
to do the dirty work. It might be enough to install a new OpenGL driver to
change CSG view results. And finally CGAL's Nef polyhedra implementation
might have its own 'opinion' about these things and also change it some day.

As I understand it, OpenSCAD currently bypasses CGAL for 2D shapes and does
some own (fast) calculations on them. So, there are at least three worlds -
and representations - involved ... 

I would always decide (and advise) to use a more common or 'straight'
solution instead of 'peek and poke' for *robustness* and execution time.
Instead of 

> hull() { sphere(5); point3([0,0,12]); 

I'd always apply 'Occam's razor' and simply write:

> hull() { sphere(5); cylinder(12, 0.1, 0); } 

And everybody (including myself even after a year) will be able to read it. 

What do you think, will be gained? More language expressiblity?




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