# Subcurve of a curve (circle) from intersection with a given length

Hi there,

As the title says, I would like to create a subcurve of a circle from an intersection point with a given length.

To be more precise, I have two curves/circles that intersect each other at two points. I would like to create a subcurve of one of the circle starting from one of the two intersection with a length determined on Grasshopper.

I have got fairly close but I don’t know how to make the subcurve start from one of the two intersection point…

Any help would be very much appreciated! Thanks so much in advance.

Something like this?

Subcurve from intersection at given length_re.gh (10.0 KB)

You are close to the solution with adjust seam

Thank you so much @HS_Kim and @anon39580149 for your very prompt replies. I very much appreciate it!

I have tried Seghier’s solution – I wasn’t familiar with filter so I’m very happy I learnt how to use it thanks to you.

One small remaining problem though… I’ve tried your GH file with a new set of curves but my desired lengths and the output length don’t match… I feel like it’s due to a silly mistake from my side but I can’t figure why even after reflecting for a while… Your help would be appreciated.

Thanks!

You can also use Evaluate length

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Really appreciate it

Hi @anon39580149 / @HS_Kim, I have an additional question if you don’t mind.
Is it possible to choose with a toggle or something the direction to which the length “goes”.

To be more precise, as illustrated below, with the same length, we could both get the yellow or pink subcurve. However, at the moment, I can only get one of them with GH.

@HS_Kim On a generic NURBS curve, the curve domain is evaluated from the control polygon and not from the curve itself. Even if you normalize it with the curve’s length, there is no reason it will evolve linearily along the curve, nor that evaluating the domain of the curve at some number will correspond to the actual length. `Evaluate Length` is the only correct answer for complex curves - yours works for lines, polylines and arcs.