If I have some arbitrary complex object, is there some method to produce a hollowed out version of it? -- View this message in context: http://forum.openscad.org/Is-there-a-way-to-make-a-skin-from-a-complex-object-tp20575.html Sent from the OpenSCAD mailing list archive at Nabble.com.

On 2017-02-25 19:17, adrian wrote: > If I have some arbitrary complex object, is there some method to > produce a > hollowed out version of it? Subtract a scaled down version. Carsten Arnholm

to amplify arnholm's reply: I have done a translate() of the difference out object to show that it did indeed "hollow" it out. $fn = 60; module object() { cylinder(r1=4, r2=10, h= 20, center=true); translate([0,0,5]) cube([20,3,3], center=true); } difference() { object(); translate([0,0,-1.5]) scale([.9,.9,.9]) object(); } -- Extra Ham Operator: K7AZJ Registered Linux User: 275424 Raspberry Pi and Openscad developer *The most exciting phrase to hear in science - the one that heralds new discoveries - is not "Eureka!" but "That's funny...".*- Isaac. Asimov On Sat, Feb 25, 2017 at 11:24 AM, <arnholm@arnholm.org> wrote: > On 2017-02-25 19:17, adrian wrote: > >> If I have some arbitrary complex object, is there some method to produce a >> hollowed out version of it? >> > > Subtract a scaled down version. > > Carsten Arnholm > > > _______________________________________________ > OpenSCAD mailing list > Discuss@lists.openscad.org > http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >

That only works for a convex shapes and doesn't necessarily give a constant wall thickness. In 2D you can use offset(-thickness) to produce a smaller to subtract. In 3D it can be done with a sequence of Minkowskis but will be very slow. On 25 February 2017 at 18:24, <arnholm@arnholm.org> wrote: > On 2017-02-25 19:17, adrian wrote: > >> If I have some arbitrary complex object, is there some method to produce a >> hollowed out version of it? >> > > Subtract a scaled down version. > > Carsten Arnholm > > > _______________________________________________ > OpenSCAD mailing list > Discuss@lists.openscad.org > http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >

Thanks Carsten and jdawgaz, but I did say complex object, so scaling will not achieve what I need (though I did try that before I posted). Thanks nophead, I did look into minkowski, but that expands the object, which isn't what I'm looking for. Any other suggestions? Thanks, -- View this message in context: http://forum.openscad.org/Is-there-a-way-to-make-a-skin-from-a-complex-object-tp20575p20579.html Sent from the OpenSCAD mailing list archive at Nabble.com.

Difference your object from a larger cube (or whatever) to get a female mould. Then minkowski that and intersect with the original object. On 26/02/2017 08:20, "adrian" <adrianh.bsc@gmail.com> wrote: > Thanks Carsten and jdawgaz, but I did say complex object, so scaling will > not > achieve what I need (though I did try that before I posted). > > Thanks nophead, I did look into minkowski, but that expands the object, > which isn't what I'm looking for. > > Any other suggestions? > > Thanks, > > > > > > -- > View this message in context: http://forum.openscad.org/Is- > there-a-way-to-make-a-skin-from-a-complex-object-tp20575p20579.html > Sent from the OpenSCAD mailing list archive at Nabble.com. > > _______________________________________________ > OpenSCAD mailing list > Discuss@lists.openscad.org > http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >

Yes exactly. I can't remember if Minkowski works on hollow objects yet. It used to be the case I had to punch a sprue hole in the mould for it to recognise the inside and then I had to cut off the resultant bleed from the object. That was probably 2D Minkowski though, before offset. On 25 February 2017 at 19:53, Frank van der Hulst <drifter.frank@gmail.com> wrote: > Difference your object from a larger cube (or whatever) to get a female > mould. Then minkowski that and intersect with the original object. > > On 26/02/2017 08:20, "adrian" <adrianh.bsc@gmail.com> wrote: > >> Thanks Carsten and jdawgaz, but I did say complex object, so scaling will >> not >> achieve what I need (though I did try that before I posted). >> >> Thanks nophead, I did look into minkowski, but that expands the object, >> which isn't what I'm looking for. >> >> Any other suggestions? >> >> Thanks, >> >> >> >> >> >> -- >> View this message in context: http://forum.openscad.org/Is-t >> here-a-way-to-make-a-skin-from-a-complex-object-tp20575p20579.html >> Sent from the OpenSCAD mailing list archive at Nabble.com. >> >> _______________________________________________ >> OpenSCAD mailing list >> Discuss@lists.openscad.org >> http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >> > > _______________________________________________ > OpenSCAD mailing list > Discuss@lists.openscad.org > http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org > >

An efficient 3D offset function would be great, and has been raised on this mailing list before, but as I understand it, it is not trivial to implement with the libraries and tools used currently. When I have needed to do this, I have used meshlab to generate offset STLs, then imported them to OpenSCAD for further manipulation. > On 26 Feb 2017, at 11:40 am, nop head <nop.head@gmail.com> wrote: > > Yes exactly. I can't remember if Minkowski works on hollow objects yet. It used to be the case I had to punch a sprue hole in the mould for it to recognise the inside and then I had to cut off the resultant bleed from the object. That was probably 2D Minkowski though, before offset. > >> On 25 February 2017 at 19:53, Frank van der Hulst <drifter.frank@gmail.com> wrote: >> Difference your object from a larger cube (or whatever) to get a female mould. Then minkowski that and intersect with the original object. >> >>> On 26/02/2017 08:20, "adrian" <adrianh.bsc@gmail.com> wrote: >>> Thanks Carsten and jdawgaz, but I did say complex object, so scaling will not >>> achieve what I need (though I did try that before I posted). >>> >>> Thanks nophead, I did look into minkowski, but that expands the object, >>> which isn't what I'm looking for. >>> >>> Any other suggestions? >>> >>> Thanks, >>> >>> >>> >>> >>> >>> -- >>> View this message in context: http://forum.openscad.org/Is-there-a-way-to-make-a-skin-from-a-complex-object-tp20575p20579.html >>> Sent from the OpenSCAD mailing list archive at Nabble.com. >>> >>> _______________________________________________ >>> OpenSCAD mailing list >>> Discuss@lists.openscad.org >>> http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >> >> _______________________________________________ >> OpenSCAD mailing list >> Discuss@lists.openscad.org >> http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >> > > _______________________________________________ > OpenSCAD mailing list > Discuss@lists.openscad.org > http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org

Thanks everyone, Due to the complexity, I've opted to make each component of the complex object to allow generating either the inner, outer or skin of the object (usually a difference operation of two sizes). This allowed me to generate the complex object using a combination of intersections and differences of the sub objects. Not trivial, but much faster than doing anything stated here. Appreciate the help though. Thanks again. A -- View this message in context: http://forum.openscad.org/Is-there-a-way-to-make-a-skin-from-a-complex-object-tp20575p20584.html Sent from the OpenSCAD mailing list archive at Nabble.com.

Would tell us what you have done with a small example? 2017-02-26 11:36 GMT-03:00 adrian <adrianh.bsc@gmail.com>: > Due to the complexity, I've opted to make each component of the complex > object to allow generating either the inner, outer or skin of the object > (usually a difference operation of two sizes).