Polyline to boundary surface issues

Hi everyone!

I have a bunch of polylines that represent water and islands, and I figured I’d use Boundary Surfaces to create the water with holes for the islands, but for some reason it does not work, and it’s driving me crazy. As far as I can see all curves are closed and planar. Any ideas what the issue might be?

Thank you

Boundary-Surface-Issues.gh (141.7 KB)

normally I will first try to explode/join/planar them in rhino:

explode all these curves into 8426 segments.
join all these 8426 segments into 162 closed planar curve.
explode again, got 8426 again.
join again, but this time got 163 closed planar curve.
both time I found no dup curves in 8426 segments.
I tried use boundary surface with 162 and 163 curves, they all returnd warning with “self intersected curve exist” (I did not use English version of rhino)

In this case I suggest using GH’s boundary surface (individually) to deal with these self intersection aotumatically.
after that, the new curve will be good to go.

Thank you dear Deer!

The boundary-back to curve thing worked great!