fix(boolean): recover coplanar boundary triangles dropped in normalization (#2111) - #2217
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…ation (#2111) TriangulatePlane classifies each candidate triangle by casting a ray from its centre and testing containment in both operands. A coplanar face whose centre lies exactly on a face of an operand is classified as neither inside nor boundary, so the triangle is dropped and the result develops a hole (the "missing geometry" family, e.g. thin walls). Rescue such a triangle inside the normalization pipeline: if its centre lies on an original face of A and is not strictly inside B, mark it as an A boundary and keep it. Recovering it here rather than stitching afterwards reuses the already-welded vertices, so no T-junctions or non-manifold edges are introduced. Fixes #2111
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Problem
TriangulatePlane(fuzzybools normalization) classifies each candidate triangle by casting a ray from its centre and testing containment in both operands. A coplanar face whose centre lies exactly on a face of an operand is classified as neitherINSIDEnorBOUNDARY, so the triangle is dropped and the boolean result develops a hole — the "missing geometry" family (e.g. thin walls, slab tops), tracked in #2111.Fix
Rescue such a triangle inside the normalization pipeline: if its centre lies on an original face of
Aand is not strictly insideB, mark it as anAboundary (recording that face's normal for correct winding) and keep it.Recovering it here — rather than stitching afterwards — reuses the already-welded vertices, so no T-junctions or non-manifold edges are introduced by the recovery. The change is gated behind the existing "both operands non-boundary" drop condition, so only triangles that would otherwise be discarded are considered.
Verification (native geomquality A/B, main vs this branch)
No model that opened before hangs or crashes. Naked-edge / non-manifold totals:
Fixes #2111