Y shaped tube junction

Hey there!
Today I was trying to model kind of a Y-shaped junction for a tube in grashopper. After some chatgpt interogation and browsing this: y shaped tube - Grasshopper was the only thread I found which sadly didnt resolve my problem. I want my Tube to make a junction/split and the after come back together. As you can see in some photoshopped pictures below or also in a simplified version of it as a pipe.

Tunnel_Y_split.gh (21.8 KB)
Thank you a lot in advance for any help!

This is how I would approach it…

tube.gh (13.3 KB)

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is there no possibility to do it directly from the geometry I did (the one with the half polygons which create a tunnel)? With your approach I would have the tube after, but not my created tunnel. Or is the only possibility to create the tube first and the from there the geometry I want?
(this was my desired result)

Your file does only contain one tunnel and no additional branch…

I reduced the number of divisions. It creates problems when you’re adding a branch.

Tunnel_Y_split.gh (44.0 KB)

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Yes I know my file only has one branch, that’s also exactly my problem. I to keep my geometry like it is and at some point add a branch, for my question here it doesnt really matter where the branch is, it can be added anywhere. As a Result I also want still to have the grid like in the file and !!NOT a pipe/SubD/Brep!! → I need Curves, those half polygons I have with the controlpoints which are connected. The result in the end should look like in this picture
also with this grid I used there and again NO SUBD/Pipe/Surface/Brep

You could extract the mesh instead of using the SubD… and refine it.

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Thank you for your help! I was hoping there was a possibility to do it directly from the polygon tunnel without the multipipe tool and without converting everything into a surface/mesh/subd/brep. Is there no solution where the outcome at the end would be only curves again? like in the beginning?

Extract mesh edges maybe?

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well yeah but I mean a way to do it from beginning to end and keeping it in curves without transforming it to a mesh or similar and back again. Because also with extracting the mesh edges or also projecting lines onto the subD I can’t reach the geometric result + the added branch that I had in a beginning with the curves. (Maybe I’m also doing something wrong)

Maybe I’m missing something…

If it wasn’t for the junctions I’d say yes stick with your process but the junctions add complexity.

Tunnel_Y_split.gh (45.9 KB)

Here’s an option with End Offset set to ‘0’ and just one level of subdivision:

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This actually resolves my problem, I was the one missing something, not you. I was just wondering if it was possible with my approach from the beginning, but as you correctly mentioned, the branch adds too much complexity. This is a perfect solution for my problem. Thank you a lot!!

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Thank you :+1:

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Small Additional question. How can I divide the list of Curves from the final output into 2 lists: one list has the vertical half-polygon curves and one has the more horizontal like curves (the ones connecting the half-polygon edges)
List 1:

List 2:

Try the Warp Weft component from the Kangaroo / Mesh tab.


exactly what I wanted! Thank you a lot have a nice evening!

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Great job, @martinsiegrist!
You are so good at the MultiPipe component.
I have a question: if the bifurcation model sections along the centerline are not circles, but irregular shapes, how can we apply this component?

You could scale the sections.

Thank you for your prompt reply, @martinsiegrist!
Do you mean to use ‘Scale’ component?
It can change the size of the section, but the shape will still be circle.