Hole Detection

[wtaisto]

I'm looking at using your lib to modify 2d texture maps on 3d meshes based on where the meshes are pressed against each other (anti-coplanar faces.) After performing an operation which returns a polygon with multiple Regions, is there a way to know if the Regions refer to holes vs freestanding polygons? In the example below, when subtracting blue from red, both scenarios return 3 Regions. From my experimenting, it appears that the first Region returned tends to be "the biggest outermost Region", but the remainder being holes or not is unclear. I tried testing to see if the vertex winding order is opposite for outlines / holes, but it did not seem to be. I've read through tutorials on this algorithm, and have a vague sense that the notion of "a RegionIS a hole or not" might itself be loosely defined.

Ultimately, I really just need to be able to take the regions that pop out of an intersection operation, and apply an earcut / tessellating algorithm to them to get a triangularized mesh. The only earcut implementations I've found specifically ask for information on where the holes are; do you know of any implementations which would work using the output of your lib?

[wtaisto]

Since the result of a boolean operation would never return regions with overlapping edges, the regions should be parseable as a "contains" tree. So a region being a hole is the same as it's node depth being even. Tessellating gets easier then; traverse the tree from the root non-hole, and if it has a hole, just combine the edges with the edges of the hole, cutting an O into a C, then tessellate that normally. Keep doing that recursively down the containment tree, voila. Maybe i'll get enthusiastic and suggest a patch.