# How to create an cylindrical arc?

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## How to create an cylindrical arc?

 I need to make an cylindrical arc given 3 points: start, middle and end.  It's been a while since I've done vector algebra, but I'm guessing I'll have to find the centre point which I would use to translate from the origin, find the plane, which I would use to rotate from the x,y plane to the actual plane, find the radius and extrude several linear segments of a circle and then rotate and translate it into position. Does that sound reasonable?  Is there another way to do this?  A prefabbed lib maybe? A
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## Re: How to create an cylindrical arc?

 Oh, I can use the rotate_extrude().  But everything else should be good right? A
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## Re: How to create an cylindrical arc?

 Actually, is it "cheaper" to make a bunch of segments and subtract the sections I don't want?  Or is it better to use a bunch of linearly extruded segments? A
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## Re: How to create an cylindrical arc?

 Actually, I think that doing a bunch of segments wouldn't work since every time I add a new segment, it would not properly intersect with the last one.  I would need some type of function to "round the corner" between one segment and the next. :( So I guess that answers my question.  Unless there is some other way to make an arc.  Unfortunately, it looks like rotate_extrude() is limited to only doing a full 360 degrees and no partial.  At least the documentation doesn't seem to indicate that it is possible... A
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## Re: How to create an cylindrical arc?

 Administrator Nice little conversation you're having with yourself ;) Try donutslice() from MCAD/2Dshapes.scad, in libraries under your OpenSCAD program installation directory. You'll need to extrude it. You should checkout all the MCAD libraries too. Cheers. Admin - email* me if you need anything, or if I've done something stupid... * click on my MichaelAtOz label, there is a link to email me. Unless specifically shown otherwise above, my contribution is in the Public Domain; to the extent possible under law, I have waived all copyright and related or neighbouring rights to this work. Obviously inclusion of works of previous authors is not included in the above. The TPP is no simple “trade agreement.” Fight it! http://www.ourfairdeal.org/ time is running out!
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## Re: How to create an cylindrical arc?

 MichaelAtOz wrote Nice little conversation you're having with yourself ;) Well, had to talk to someone intelligent around here. ;) MichaelAtOz wrote Try donutslice() from MCAD/2Dshapes.scad, in libraries under your OpenSCAD program installation directory. You'll need to extrude it. You should checkout all the MCAD libraries too. Oh, that's good to know.  Didn't look around the file system for that. Thanks, A
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## Re: How to create an cylindrical arc?

 Administrator You should also do a search for OpenSCAD on thingiverse.com, there are some good libraries there. Admin - email* me if you need anything, or if I've done something stupid... * click on my MichaelAtOz label, there is a link to email me. Unless specifically shown otherwise above, my contribution is in the Public Domain; to the extent possible under law, I have waived all copyright and related or neighbouring rights to this work. Obviously inclusion of works of previous authors is not included in the above. The TPP is no simple “trade agreement.” Fight it! http://www.ourfairdeal.org/ time is running out!
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## Re: How to create an cylindrical arc?

 Documentation is sparse on donutSlice().  From what I can see, it makes a blocky donut slice.  Not very useful. :/ A
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## Re: How to create an cylindrical arc?

 Administrator If you mean the line segments, try donutSlice(30,50,190,270,\$fn=64); Admin - email* me if you need anything, or if I've done something stupid... * click on my MichaelAtOz label, there is a link to email me. Unless specifically shown otherwise above, my contribution is in the Public Domain; to the extent possible under law, I have waived all copyright and related or neighbouring rights to this work. Obviously inclusion of works of previous authors is not included in the above. The TPP is no simple “trade agreement.” Fight it! http://www.ourfairdeal.org/ time is running out!
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## Re: How to create an cylindrical arc?

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## Re: How to create an cylindrical arc?

 In reply to this post by MichaelAtOz Well that's less blocky but its too big and I also want a circle extruded along an arc.  I've been looking around and it looks like sweep() is what I'm looking for, but I need to figure out how it works and where all the modules are to use it.  I see it here, but some of the modules it includes are not there. A
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## Re: How to create an cylindrical arc?

 In reply to this post by Ian Nichols Thanks Ian!  That has good possibilities. :) A
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## Re: How to create an cylindrical arc?

 Administrator In reply to this post by adrian adrian wrote but some of the modules it includes are not there. You need the development version to use it. Admin - email* me if you need anything, or if I've done something stupid... * click on my MichaelAtOz label, there is a link to email me. Unless specifically shown otherwise above, my contribution is in the Public Domain; to the extent possible under law, I have waived all copyright and related or neighbouring rights to this work. Obviously inclusion of works of previous authors is not included in the above. The TPP is no simple “trade agreement.” Fight it! http://www.ourfairdeal.org/ time is running out!
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## Re: How to create an cylindrical arc?

 Administrator In reply to this post by adrian > too big and I also want a circle extruded along an arc. IOW a curved tube?? Admin - email* me if you need anything, or if I've done something stupid... * click on my MichaelAtOz label, there is a link to email me. Unless specifically shown otherwise above, my contribution is in the Public Domain; to the extent possible under law, I have waived all copyright and related or neighbouring rights to this work. Obviously inclusion of works of previous authors is not included in the above. The TPP is no simple “trade agreement.” Fight it! http://www.ourfairdeal.org/ time is running out!
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## Re: How to create an cylindrical arc?

 Administrator In reply to this post by adrian On Jan 28, 2015, at 22:03 PM, adrian <[hidden email]> wrote: > Well that's less blocky but its too big and I also want a circle extruded > along an arc.  I've been looking around and it looks like sweep() is what > I'm looking for, […] Sweep is a bit general and probably requires too much configuration to fit your needs perfectly. Currently, the best solution I can think of is to just intersect your 360 degree rotation volume with a wedge. Here’s a quick starting point: module rotate_extrude_angle(angle, size) {   module pie(a) {     r=sqrt(2);     hull() polyhedron(points=[[0,0,-r], [r,0,-r], [r*cos(a),r*sin(a),-r],[0,0,r], [r,0,r], [r*cos(a),r*sin(a),r]], faces=[[0,1,2,3,4,5]]);   }   intersection() {     scale(size) pie(angle);     rotate_extrude() children();   } } rotate_extrude_angle(45, 13) translate([8,0]) circle(5);  -Marius _______________________________________________ OpenSCAD mailing list [hidden email] http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org
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## Re: How to create an cylindrical arc?

 Administrator OpenCSG doesn't like that Admin - email* me if you need anything, or if I've done something stupid... * click on my MichaelAtOz label, there is a link to email me. Unless specifically shown otherwise above, my contribution is in the Public Domain; to the extent possible under law, I have waived all copyright and related or neighbouring rights to this work. Obviously inclusion of works of previous authors is not included in the above. The TPP is no simple “trade agreement.” Fight it! http://www.ourfairdeal.org/ time is running out!
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## Re: How to create an cylindrical arc?

 Administrator On Jan 29, 2015, at 00:04 AM, MichaelAtOz <[hidden email]> wrote: > OpenCSG doesn't like that > Yep, quick and dirty. the rotate_extrude() needs a convexity parameter to render correctly. I guess we could be helpful and automatically set it higher for rotate_extrude as it tends to always have a depth complexity of minimum 2..  -Marius   _______________________________________________ OpenSCAD mailing list [hidden email] http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org
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## Re: How to create an cylindrical arc?

 Administrator On Jan 29, 2015, at 00:08 AM, Marius Kintel <[hidden email]> wrote: >  I guess we could be helpful and automatically set it higher for rotate_extrude as it tends to always have a depth complexity of minimum 2.. > Fixed in latest master ;)  -Marius _______________________________________________ OpenSCAD mailing list [hidden email] http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org
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