Match points with opposite ones

[William_Felcone]

Hello,

I have two sets of arcs which combine to create a shape. The number of arcs is variable. I would like to select specific, opposite pairs of arcs so I can use them to make other geometry. Additionally, I would like to specifically select the pair of arcs that runs along the y axis.

I cannot figure out how to select the arcs in pairs, or how to select the pair that runs along the y axis. It is also important that this be able to work if there are more or fewer pairs of arcs.

Thank you

Sept 24 Grasshopper Plan 1.gh (80.8 KB)

[Joseph_Oster]

Wow! Where to begin?

Many ways, you could do this:

Grasshopper Plan_2024Sep24a.gh (56.5 KB)

[ftzuk]

Branch selecting at the end is just for coloring.

CURVES.gh (61.9 KB)

[Joseph_Oster]

Looking at only your results (image), not your code:

Grasshopper Plan_2024Sep24b.gh (62.5 KB)

[seltzdesign (Armin Seltz)]

You can just create a line in the direction you want to check and then check for intersections with that line:

Sept 24 Grasshopper Plan 1_findarcs.gh (62.1 KB)

[William_Felcone]

Thank you, this one does not quite work because when I change the number of sides of the polygon (the variable in the very first group) the selected arcs are not opposite each other.

[William_Felcone]

Thank you, this does work when the number of polygon sides are changed, but I have to keep working on the file some more before I can determine if this is all I need

[Joseph_Oster]

@William_Felcone

Thank you, this one does not quite work

That’s because of how you create the regions. Easily fixed by replacing the shift list slider with an expression: (x+1)/2

Grasshopper Plan_2024Sep24c.gh (63.6 KB)

P.S. You could also do this by rotating the polygon appropriately but I won’t touch that because I’m afraid once I start to modify your code, I might re-write most of it.

[Joseph_Oster]

@Joseph_Oster

I’m afraid once I start to modify your code, I might re-write most of it.

I tried to ignore it but hope you will consider this:

Grasshopper Plan_2024Sep24d.gh (30.6 KB)

Image shows complete file.