Geonodes. Selecting rings of an spline+Arc based mesh. How would you do this?

My approach was wierd and based on experiments and a bit wierd calculations like "here’s the experimental “magic number” which work. How i can get this number based on numbers which i already have like resolution and so on. Which number i can multiply, divide or add to get the “magic number”.
Eventually i can notice some “system” in numbers and form a formula.

It leads me to my solution which works, but only for spline mesh based on Arc.

Im not skilled in geonodes and all that “index math”, so i wonder maybe some one have different methods for such selections and it are more easy and understandable?

Here’s my method:


arc_ring_select.blend (985.7 KB)

Here:

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Oh. Definitely more easier solution than mine. Thanks for sharing :slight_smile:

I did a bunch of this index-style sorting of rings along curves and toruses in my first big GN project. You can get it for free here, it’s got it stored in a bunch of node groups for the tesla coil.

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Why so much math?

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For ability to offset and skip certain amount of rings

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Ok, but you just eliminated a multiply at the expense of storing the height index on the geom.

Correction… 2 multiplies…

Additionally, replacing the Index with Spline Parameter Index you get something which becomes agnostic of the curve and profile dimensions (and works with multi-curve setups):

Yeah I meant the multiply of the inputs, you saved that at the cost of storage space. Thanks for counting. It was rather a comment on your “so much math”, but forget about it.

Forget about what?

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