Fill planar holes in mesh space

[Grantim]

What

Two commits:

1. fillContours2D fills holes in mesh space. The hole loops go through triangulateDisjointContours( mesh, loops, normal, nullptr, &patchToMesh ) and the patch is stitched through the patch→mesh edge map, aligned to the input loops by identity. Deleted: the best-fit-plane projection round-trip (projectHoles/fillProjected), the HolesVertIds-driven vertex merge, and the border point snap-back — patch boundary vertices now carry the exact mesh coordinates by construction. validateAndFixPatch and the addMeshPart stitch are unchanged.
2. SweepLineQueue: insert pinch-ring edges geometrically in the sweep frame. The copied ring order comes from the input surface, whose facing is independent of the patch normal the sweep frame follows; at a vertex the boundary visits twice the inherited order could pair the wrong sectors and the fill came out folded (correct net winding, faces of both senses — e.g. a two-lobe "bowtie" hole filled as the whole quadrilateral plus two reversed triangles). Both splices of a new patch edge are now deferred until its endpoints are known and anchored with findClosestToFront in projected coordinates (new overload taking the reference-ray base explicitly) — the same rule mergeSamePoints_ uses, so pinched fills match the contour-rebuild path exactly. This fixes the mesh-space triangulation itself, not only fillContours2D.

Verification

• Differential test over 2770 planar-hole meshes (random simple polygons, quantized degenerate stars, sphere trims, annulus meshes with two loops filled jointly) vs the old projection path: every in-contract case agrees on all invariants (faces, verts, holes closed, multiple edges, filled area, orientation); the 2160 polygon cases produce byte-identical triangulations, including 27 pinched (self-touching) boundaries the pre-fix copy folded.
• Six cases that crash the old fillContours2D with heap corruption (quantized self-touching boundaries; reproduced on clean master) return a clean error instead.
• Pinch fix exercised across the configuration space: loop normal on all 6 signed axes, in-plane rotations 0–90°, tilted planes off every axis, pinch vertex displaced ±1e-6..±0.05, both surface orientations — all clean, patch always faces the passed normal.
• End-to-end boolean digest (rotating spheres, 200 frames): byte-identical to master.
• MRTest suite passes, with new pinched-boundary tests at both levels (fillContours2D and triangulateDisjointContours).
• Perf (alternating-process A/B vs master, medians over 28 rounds, decimate control flat): 956 small planar holes in one call −6.1%, one big trim hole −7.9%, two-loop annulus −6.5%.

Follow-ups (separate PRs)

1. Delete the then-unused machinery: outBoundaries mesh-overload parameter and its rebuild branch, 2D holeVertsIds/outBoundaries parameters, HolesVertIds types and findHoleVertIdsByHoleEdges, the identity-guard in mergeSamePoints_.
2. cutMesh joint per-old-face hole fill on top.

🤖 Generated with Claude Code

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