Hi Marco, it sounds like that might work but I haven't analyzed what you've got there in detail yet.

The Construct > Planar command does do this type of hole detection as part of how it functions, so maybe another possible way could be to just send all the curves through PlanarSrf, then in the breps that were generated from that get the brep face and on the face call getLoops() - if a face has more than one loop all the loops after the first one are holes, the first loop is the outer boundary. So for every hole you detected there you'd need to identify the original curve it came from, maybe scanning through your curves and seeing if they have the same start/end points would work. For segmented curves like a square with 4 segments in it that will have 4 separate edges in the loop.

- Michael