Howard Trickey
6543290116
The face merging code in exact boolean made an assumption that the tesselated original face was manifold except at the boundaries. This should be true but sometimes (e.g., if the input faces have self-intersection, as happens in the example), it is not. This commit makes face merging tolerant of such a situation. It might leave some stray edges from triangulation, but it should only happen if the input is malformed. Note: the input may be malformed if there were previous booleans in the stack, since snapping the exact result to float coordinates is not guaranteed to leave the mesh without defects.