Grasshopper Intersect curves not acting as expected

Good morning,

So I’m trying to make a grasshopper definition to create a series of flats based on a shape. Currently I’m just working out how to take the skin (plywood) and break it up into it’s sheet good size. My next step would be to create framing either wood w/ pockets or steel based off the new set of surfaces.

I’ve got a couple questions.
1: My last line that’s created doesn’t intersect (using MCX) with the other lines. Is this due to it being merged data?
2: My intersect curves shows points intersecting (except the last line again) but still throws a warning that I need to input atleast two sets of curves in each direction. Is this a bug? Picture below.

Do you think I’m on the right path, or have I taken the long way to get a surface divided into sections?



Surface to Parametric (21.4 KB)


  1. In the input “CU” of intersect curves just flatten them and it will work perfectly
  2. the point is there, you just can’t see it because it coincides with the initial points. (if you see the output, it has (2*7=) 14 points.)
    If you turn off the preview for the initial points you will see it green and shinny!
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One thing to note is that if you do not do flattening before MCX, data matching occurs between lines with the same path.
This is a typical data matching problem, and it’s always a good idea to confirm the data tree structure.
See attached screen grabs.

Hi @ra_mull,

I am not sure I fully understand what you are trying to achieve with the definition, but maybe this helps (see attached gh file).


Surface to Parametric (19.4 KB)

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I did try flatten but I was using it farther upstream which messed all sorts of things up.

That helped with the “MCX” also.

Thanks for the visual,
I’ll check the data structure next time.

Hi @Lina,

That’s the first part of what I am trying to achieve. Looks as though I was taking the long way around. I was going to use the intersecting points to make a bunch of surfaces for my skins of the walls.

That’s a much simpler approach to split the surface with the curves.