Can't split mesh

i tried mesh split and mesh split plane, both give odd results (geometry seems ok).
i attached the def if anyone is willing to take a look…
thanks for your interest!

mesh split (22.2 KB)

I’m afraid your mesh is not a good one thought…

There are 1,800 duplicated faces in your bad mesh.

Here is a solution but I have no idea how the Mesh Split Planewould identify the above and bellow plane in this case.

You’ll need Meshedit plugin.

mesh split (14.9 KB)

Thanks for pointing that out! I ll get to the root of it.

it’s so weird, it gives the proper result if I generate a mesh based on the bad one like you did in the definition you sent (thank you by the way!), but it doesn’t work if i generate a simple flt mesh or if i make it curved but without the doubling. i attached the file if you still want to take a look…mesh split (32.0 KB)