If I have understood well your improvement, the bounding box of the
following solid might not overestimate the true bounding box:

difference(){
cube([100,100,20],center=true);
difference(){
cube(200);
cube([100,100,20],center=true);
}
}

2017-08-13 19:13 GMT+01:00 Carsten Arnholm arnholm@arnholm.org:

On 13. aug. 2017 21:05, Ronaldo Persiano wrote:

Slightly odd example, as you just end up with the first cube

shape@ main_shape()
{
solid@ c1 = cuboid(100,100,20,center:true);
solid@ c2 = cube(200);
return print_box(c1 - (c2 - c1));
}

boundingbox: x=[-50,50]  y=[-50,50]  z=[-10,10]

So yes, no overestimation in this case.

Carsten Arnholm

Jordan said: "All that said, for today's project a simplistic unioned
bounding box that can be used for positioning would be helpful :-)"

The "General Library of Relativity" implements approximate bounding boxes
in OpenSCAD, and provides a general facility "to size, position, and orient
objects relative to other geometric primitives."

https://www.thingiverse.com/thing:349943

It works by wrapping all of the geometric primitives in new modules with
different names, and determining bounding boxes from module arguments:
'cube' becomes 'box', 'rotate' becomes 'rotated', etc. Unfortunately,
because the underlying functionality isn't built in, the Relativity library
can't determine the bounding box of an STL file :-(.

On 14 August 2017 at 00:20, Jordan Brown openscad@jordan.maileater.net
wrote:

On 8/14/2017 5:33 AM, doug moen wrote:

Interesting, thanks.  I haven't really wrapped my head around what it
means, but it looks pretty cool.  It looks like some of the stuff I've
done (e.g. cubes that will justify or center against any side), but
multiplied by a hundred.

On 14/08/17 16:57, Jordan Brown wrote:

The very cool bit is that you can (with some effort) get the negative
spaces in modules to "propagate" such that they make holes in other things.

I kind of do the same with a special variable called $Negative, which
lets my invoke a whole tree of stuff twice, once for positive parts and
once for holes, but Relativity makes it much neater.