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I'd like to start with a curve circle, as if it was projected on a tube. Then make it a solid ribon with an even width thicknes, of some hight. In below i used cast modifier, a circle and some geometry nodes to get it but its not OK. As I want to endup with a solid mes and start with a curve circle. So it then the end it be like a frame for glass on a airplane, or rocket. (that kind of shape)

I'd like to add bolts onto it following the shape from the front (y axis).

Its something that will egt 3d printed, for an artistic idea, but i cannot get the basic shape right. (I dont want a half solution like i made below, because eventually this gets high resolution printed, and then the 'casting effect as i have in below' can be removed by seting a high faces value for a cylindric geometry mesh just before i print it).

But how to create such a shape purely by geomotry nodes, so that the eventually printed part be of good solid geometry and perfectly fit an existing tube. (notice the bolts are a high requirement for me, i probaply figure it out once i understand how to make this shape), but for now whatever i try i always got those U bands and not solids, or shapes with wrong internals for printing, so anyone have an idea on how to do this ?.

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  • $\begingroup$ Is it absolutely necessary to create it in Geometry Nodes? $\endgroup$
    – Gordon Brinkmann
    Commented May 30, 2022 at 8:56
  • $\begingroup$ Yes it is, i can do it without geometry nodes but then i aply 'a super resoltion thats no problem what i want here is understand how to do it in geometry nodes so i can work in low versions, and just before printing alter some atributes and create a high res STL. Also for some other things i'll add later i depend on the nodes $\endgroup$
    – Peter
    Commented May 30, 2022 at 14:50

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  1. You can create the desired shape by lining up the nodes Extrude Mesh and Flip Faces.

  2. In order for this to be projected onto the surface of a cylinder, you apply the formula $r*\cos(\arcsin({{s}\over{2r}}))$ for the offset. This calculates the angle for the points on the X-axis towards the center and distributes the points along the Y-axis using this angle.

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  • $\begingroup$ Oh wow thanks a lot man, its exactly as how i wanted it to be, the band has no strange distortions, and fits perfectly a cylinder while it is a circle. And i can learn from this as well thanks again !! $\endgroup$
    – Peter
    Commented May 30, 2022 at 21:55
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According to official documentation:

The operations are similar to the extrude tools in mesh edit mode, though there are some differences. Most importantly, the node never keeps the back-faces of the extrusion in place, they are always removed.

So to build this you should get original faces, flip normals and join them to the extruded geometry:

enter image description here

Merge by distance is useful to have the object manifold.

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  • $\begingroup$ Yesterday i got something similair by circle curve made of 4 point over a circle curve then there is no issue with backfaces either, its a starter though the question is a bit more complex $\endgroup$
    – Peter
    Commented May 30, 2022 at 21:52

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