Good evening, I need some help, I should split an open mesh with curve as in the pictures. How do I do it with grasshopper?
Thank you
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Definitely going to need a gh file with internalized geometry. 
prova split.gh (2.8 MB)
thank you
Looks like something that @PeterFotiadis would know how to do.
He is a pro at scripting this kind of stuff.
You might try extruding your curve along the z axis and then splitting with the resulting extrusion… Considered trying that but the computing was taking to long.
thank you, i tried to do as you suggested but it requires a lot of time.
No need for code (well … in theory [and assuming lot’s of right Karma]). Just turn crv into a Mesh and split the ugly thing (or things):
Of course doing this via code would allow lot’s of checks and progress reports etc etc.
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I’ve tried many things, often through ignorance about meshes, sometimes way too slow. Here is something that works quickly and reveals some things about the curve; it’s not always on the mesh surface (faces) and in some cases doubles back on itself.
prova split_2023Oct2b.gh (2.8 MB)
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Improve the mesh or improve the curve? LoL - as it’s been pointed out, there are parts where the curve does not touch the mesh - then if this curve is projected to the mesh, the result is quite bad.
If you project the curve then clean it up a bit and extrude as a solid mesh the result is still not very useful.
Not necessarily too slow but not good either…but hey, it’s split. Split region is invalid, though. Use Combine&Clean afterwards I guess. 
I didn’t even want to try mesh difference.
prova split.gh (2.8 MB)
Good luck
Thank You very much. So you have a .gh file to understand how to do?
If you can read C# … maybe. If you can’t consider a big switch (i.e. start walking the C# walk, time flies).
Mesh_Split_JustAStupidTest_V1.gh (389.8 KB)
TIP: Put your stuff as near the global origin as possible (Meshes work with floats … meaning possible failures due to accuracy etc etc).
NOTE: Avoid at any cost to overdue your splitter Polyline. This means: avoid small segments, too much “detail” etc etc. After all … all that are in a way like using multi Clip planes (so to speak). In the atteched no elaborated tests for the splitter are included (for instance: max N of vertices, min segment length, self Ccx Events, check splitterMesh for disjoined pieces [life sucks] … etc etc).
NOTE: If inspection is your goal then a rather better option (via OpenGL etc) is using collections of Clip planes. Rhino supports that kind of stuff (but in a very primitive way).
Like:
NOTE: Mesh Split works when it works (Karma a must).
Update: added some stuff more (and a splitter List support). But still you can get rather easily bananas since Mesh.Split is a bit temperamental (at best). That said the standard RC Mesh.Split Method using a List of splitters … well … it’s not the thing to use (thus an “explicit” Method is used).
Mesh_Split_JustAStupidTest_V1B.gh (389.9 KB)
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