# "Inside minkowski"?

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## "Inside minkowski"?

 Minkowski works by (conceptually, I'm sure the practical workings to achieve it under the hood are different) basically sliding the the second objects center along the surface of the first, and then adding up all covered spaces. This means that, for example, if I want to make a rounded cube, I must subtract the diameter of the ball from the size of the cube. Sure, I can do that, but if I want a more complex form rounded, my brain soon starts to hurt. So, I thought, what if one did something like the minkowski, but instead of sliding the center along the surface, we use the surface of the second object as the contact point. That way, the dimensions of the first object will be maintained, and the edges would be rounded (or whatever you want to do). Is there any way to do that? -- Sent from: http://forum.openscad.org/_______________________________________________ OpenSCAD mailing list [hidden email] http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org
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## Re: "Inside minkowski"?

 For 2D you can offset inwards and the outwards by the same amount.For 3D you can probably make a negative object by subtracting the original from a big cube, offset with Minkowski to make the inside smaller and subtract from the original, then offset outwards with a second Minkowski, but that can get slow.On 16 March 2018 at 12:32, Troberg wrote:Minkowski works by (conceptually, I'm sure the practical workings to achieve it under the hood are different) basically sliding the the second objects center along the surface of the first, and then adding up all covered spaces. This means that, for example, if I want to make a rounded cube, I must subtract the diameter of the ball from the size of the cube. Sure, I can do that, but if I want a more complex form rounded, my brain soon starts to hurt. So, I thought, what if one did something like the minkowski, but instead of sliding the center along the surface, we use the surface of the second object as the contact point. That way, the dimensions of the first object will be maintained, and the edges would be rounded (or whatever you want to do). Is there any way to do that? -- Sent from: http://forum.openscad.org/ _______________________________________________ OpenSCAD mailing list [hidden email] http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org _______________________________________________ OpenSCAD mailing list [hidden email] http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org
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## Re: "Inside minkowski"?

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## Re: "Inside minkowski"?

 What you seem to want is a 3D version of "offset()" for automated rounding, bevelling and maybe filleting.  ( https://en.wikibooks.org/wiki/OpenSCAD_User_Manual/The_OpenSCAD_Language#offset )   That's not so easy to do.​It is not efficient but it has been solved:https://en.wikibooks.org/wiki/OpenSCAD_User_Manual/Tips_and_Tricks#Filleting_objectsMay be  also relevant  this discussion:​ _______________________________________________ OpenSCAD mailing list [hidden email] http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org
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## Re: "Inside minkowski"?

 > https://en.wikibooks.org/wiki/OpenSCAD_User_Manual/Tips_and_Tricks#Filleting_objectsPretty sure that there's a minus sign is in the wrong place on that, and it should be: >         offset_3d(-4) offset_3d(4) // interior fillets -- Sent from: http://forum.openscad.org/_______________________________________________ OpenSCAD mailing list [hidden email] http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org
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## Re: "Inside minkowski"?

 > https://en.wikibooks.org/wiki/OpenSCAD_User_Manual/Tips_and_Tricks#Filleting_objects Pretty sure that there's a minus sign is in the wrong place on that, and it should be: >         offset_3d(-4) offset_3d(4) // interior fillets ​Nice catch. Updated.​ _______________________________________________ OpenSCAD mailing list [hidden email] http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org
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## Re: "Inside minkowski"?

 In reply to this post by NateTG > "Use the surface as a the contact point" doesn't make sense - there are lots of points on the surface.  Also if you pick any particular point on the surface, you just end up with the minkowski sum again. It's hard to explain in words. I'll try a simple example: I want rounded corners on a box. So, this operation would, basically, take a sphere and move it around inside the box, as if it was rolling on the inside (except, of course, that it wouldn't actually rotate). So, basically, it's trapped inside, and moves everywhere it can, but can't go further when surfaces touch (any point on either surface). -- Sent from: http://forum.openscad.org/_______________________________________________ OpenSCAD mailing list [hidden email] http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org
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## Re: "Inside minkowski"?

 Troberg wrote > ... > > I'll try a simple example: I want rounded corners on a box. So, this > operation would, basically, take a sphere and move it around inside the > box, > as if it was rolling on the inside (except, of course, that it wouldn't > actually rotate). So, basically, it's trapped inside, and moves everywhere > it can, but can't go further when surfaces touch (any point on either > surface). > ... That's what the 'exterior fillet' example Ronaldo linked to does.  (Though you might want to get a cup of coffee while that calculates.) -- Sent from: http://forum.openscad.org/_______________________________________________ OpenSCAD mailing list [hidden email] http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org