# best way to create this

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## best way to create this

 I am sort of new and I manage to get along but probably not in the best or most efficient way. I marvel at some of the code I see. I want to create this and want to know the best way. All I come up with is a series of thin triangles in a arc, each a different size. How do I do it? thanks Lee _______________________________________________ OpenSCAD mailing list [hidden email] http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org curve.png (10K) Download Attachment
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## Re: best way to create this

 If those a circular arcs, it's a really easy case for difference(). If not, you can probably still do it that way, but depending on how you want to define the curves, a chain hull might be easier. On Feb 25, 2021, 13:44 -0800, Lee A <[hidden email]>, wrote: I am sort of new and I manage to get along but probably not in the best or most efficient way. I marvel at some of the code I see. I want to create this and want to know the best way. All I come up with is a series of thin triangles in a arc, each a different size. How do I do it? thanks Lee _______________________________________________ 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: best way to create this

 In reply to this post by Leea I think you need to give more information about what you're trying to create.  Is the shape defined by the dimensions of the triangles?  The space between them?  Or maybe by some dimensions and some angles?  And then an altitude?   Are the arcs circles?   They don't look like it, so maybe not.  What defines the arcs?   I think knowing exactly what you're trying to create is an important first step.   Leea wrote I am sort of new and I manage to get along but probably not in the best or most efficient way. I marvel at some of the code I see. I want to create this and want to know the best way. All I come up with is a series of thin triangles in a arc, each a different size. How do I do it? thanks Lee _______________________________________________ OpenSCAD mailing list [hidden email]http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.orgcurve.png (10K) Sent from the OpenSCAD mailing list archive at Nabble.com._______________________________________________ OpenSCAD mailing list [hidden email] http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org
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## Re: best way to create this

 In reply to this post by Whosawhatsis I know about Hull but what is a Chain Hull? Lee On 2/25/2021 3:50 PM, Whosawhatsis wrote: > If those a circular arcs, it's a really easy case for difference(). If > not, you can probably still do it that way, but depending on how you > want to define the curves, a chain hull might be easier. > On Feb 25, 2021, 13:44 -0800, Lee A <[hidden email]>, wrote: >> I am sort of new and I manage to get along but probably not in the best >> or most efficient way. I marvel at some of the code I see. I want to >> create this and want to know the best way. All I come up with is a >> series of thin triangles in a arc, each a different size. How do I do it? >> >> >> >> thanks >> Lee >> >> >> >> >> _______________________________________________ >> 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_______________________________________________ OpenSCAD mailing list [hidden email] http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org
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## Re: best way to create this

 In reply to this post by adrianv It is defined by the dimensions of the triangles. I am trying to figure out how to explain it. Imagine a triangular 'rod' that diminishes in size in all three dimensions from one end to the other. Then bend that rod into a U shape. So it is a solid piece. The inner arc is small and could be a circle. The outer arc is almost half a circle but a bit elliptical. It could be circle if needed. Ideally the hypotenuse would be a little concave but I was going to live with straight. I was hoping a picture was worth a lot of words. Lee On 2/25/2021 3:59 PM, adrianv wrote: > I think you need to give more information about what you're trying to > create.  Is the shape defined by the dimensions of the triangles?  The > space between them?  Or maybe by some dimensions and some angles?  And > then an altitude?   Are the arcs circles? They don't look like it, so > maybe not.  What defines the arcs? > > I think knowing exactly what you're trying to create is an important > first step. > >     Leea wrote >     I am sort of new and I manage to get along but probably not in the >     best >     or most efficient way. I marvel at some of the code I see. I want to >     create this and want to know the best way. All I come up with is a >     series of thin triangles in a arc, each a different size. How do I >     do it? > > > >     thanks >     Lee > > > > >     _______________________________________________ >     OpenSCAD mailing list >     [hidden email] >     >     http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org>     > > >     curve.png (10K) >     >     > > > > ------------------------------------------------------------------------ > Sent from the OpenSCAD mailing list archive > at Nabble.com. > > _______________________________________________ > 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: best way to create this

 Your picture looked like a flat 2d picture of triangles and an arc.  So Is this sort of like what you're after? Note: the triangles are coplanar but it doesn't look like it because of the shrinkage along the length which means the small one is not aligned with the big one. Leea wrote It is defined by the dimensions of the triangles. I am trying to figure out how to explain it. Imagine a triangular 'rod' that diminishes in size in all three dimensions from one end to the other. Then bend that rod into a U shape. So it is a solid piece. The inner arc is small and could be a circle. The outer arc is almost half a circle but a bit elliptical. It could be circle if needed. Ideally the hypotenuse would be a little concave but I was going to live with straight. I was hoping a picture was worth a lot of words. Lee On 2/25/2021 3:59 PM, adrianv wrote: > I think you need to give more information about what you're trying to > create.  Is the shape defined by the dimensions of the triangles?  The > space between them?  Or maybe by some dimensions and some angles?  And > then an altitude?   Are the arcs circles? They don't look like it, so > maybe not.  What defines the arcs? > > I think knowing exactly what you're trying to create is an important > first step. > >     Leea wrote >     I am sort of new and I manage to get along but probably not in the >     best >     or most efficient way. I marvel at some of the code I see. I want to >     create this and want to know the best way. All I come up with is a >     series of thin triangles in a arc, each a different size. How do I >     do it? > > > >     thanks >     Lee > > > > >     _______________________________________________ >     OpenSCAD mailing list >     [hidden email] >     >     http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org>     > > >     curve.png (10K) >     >     > > > > ------------------------------------------------------------------------ > Sent from the OpenSCAD mailing list archive >  at Nabble.com. > > _______________________________________________ > 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 Sent from the OpenSCAD mailing list archive at Nabble.com._______________________________________________ OpenSCAD mailing list [hidden email] http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org
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## Re: best way to create this

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## Re: best way to create this

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## best way to create this

 In reply to this post by Leea Not exactly sure that I understand what you want. This is another approach where I started with a cylinder and subtracted the bits that I wanted to eliminate. Perhaps with the right scaling and translating of the circle, you can get the shape that you want. It will not give you triangles at the edges but will give you a nice concave pocket. \$fn=100; height=20; base=30; difference(){     cylinder(h=height,r=base);     union(){       translate([-100,-50,-9]){cube([100,100,base]);}       translate([5,10,34]){scale([1,1.5,1]){sphere(r=35);}}         } } If this doesn't quite give you want you want, I hope it gives you some more ideas about how to use difference and the other tools to make something by subtracting shapes. Ron On 2021-02-25 11:15 p.m., Lee A wrote: \$fn=100; height=20; base=30; for (i=[0:1:180]){     rotate ([0,0,-i]){         translate ([-base-3+(i/10),0,0])         rotate ([270,0,0]){             linear_extrude(height = 1, center = false, convexity = 10, twist = 0)             polygon (points=[[0,0],[0,-height+(i/15)],[base-(i/10),0]]);         }     } } -- Ron Wheeler Artifact Software 438-345-3369 [hidden email] _______________________________________________ OpenSCAD mailing list [hidden email] http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org
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## Re: best way to create this

 In reply to this post by Leea I don't see what the problem is. All you need is the artistic vision of Michelangelo and the mathematical capabilities of Laplace, then this type of problem is trivial. However for the rest of us....  From your original (red?) image it looks as if it is half a cylinder, with an the top sliced off at an angle. I would do that by making a large cube, to slice the side off the cylinder, and rotate it to slice off the top at an angle. If the top needs to be concave, then use a large sphere to slice off the top. This is on the basis that if it looks right, then it is right. If it is a one off, then nothing wrong with getting the final shape you want by manually cutting/grinding. If the exact shape is not necessary, then chase a shape you can more easily generate. On 26/02/2021 04:15, Lee A wrote: > 1)  No you don't have one. If you did it would be easier to describe. > Two of them pushed together (one a mirror image) would make sort of an > egg holder. > 2)  No > etc... _______________________________________________ OpenSCAD mailing list [hidden email] http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org
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## Re: best way to create this

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## Re: best way to create this

 In reply to this post by Leea There is a simple way to construct your amphitheater with native modules: r1 = 100; r2 = 20; dx = 30; h = 80; intersection() { difference() { translate([-dx, 0, 0]) cylinder(r=r1-dx, h=h); cylinder(r1=r2, r2=r1, h=h+.1); } translate([-r1, 0, 0])cube([2*r1, 2*r1, h]); } Sent from the OpenSCAD mailing list archive at Nabble.com._______________________________________________ OpenSCAD mailing list [hidden email] http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org
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## Re: best way to create this

 You are missing the desire that the hypotenuse of the triangle be curved---a bowl shape.  I think possibly subtracting a sphere from a cylinder may work (as I suggested in my message) but it will not create a shape that is as described because the curvature will be the same on both sides and the outside shape will be circular, which is not what you get if you take a tapered triangular prism and bend it in a U shape.  So it depends on exactly what the requirements for the shape are.     Parkinbot wrote There is a simple way to construct your amphitheater with native modules: -- Sent from: http://forum.openscad.org/_______________________________________________ OpenSCAD mailing list [hidden email]http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org Sent from the OpenSCAD mailing list archive at Nabble.com._______________________________________________ OpenSCAD mailing list [hidden email] http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org
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## Re: best way to create this

 The ability to scale/distort the sphere prior to subtracting it from the cylinder gives some more flexibility in the shape of the resulting amphitheater. On 2021-02-27 11:03 a.m., adrianv wrote: You are missing the desire that the hypotenuse of the triangle be curved---a bowl shape.  I think possibly subtracting a sphere from a cylinder may work (as I suggested in my message) but it will not create a shape that is as described because the curvature will be the same on both sides and the outside shape will be circular, which is not what you get if you take a tapered triangular prism and bend it in a U shape.  So it depends on exactly what the requirements for the shape are.     Parkinbot wrote There is a simple way to construct your amphitheater with native modules: -- Sent from: http://forum.openscad.org/ _______________________________________________ OpenSCAD mailing list [hidden email] http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org Sent from the OpenSCAD mailing list archive at Nabble.com. _______________________________________________ OpenSCAD mailing list [hidden email] http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org -- Ron Wheeler Artifact Software 438-345-3369 [hidden email] _______________________________________________ OpenSCAD mailing list [hidden email] http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org
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