FA-88574 / Mesh topology invariants / Member archive

Compaction numbers vertices in first-use order · case 04

The output vertex order depends on face order instead of the original index order.

Member previewVariant 4 · 3 implementations · 7 checks per implementation

Case contract

Input [verts, faces]: drop faces with fewer than 3 distinct vertices, then keep only vertices referenced by remaining faces, renumbered 0-based in increasing old-index order. Faces keep their corner order. Return [kept vertex payloads, remapped faces].

Why this case matters

Mesh processing pipelines (remeshing, export, simulation, printing) trust these topological counts and adjacency answers; a wrong invariant silently accepts broken meshes or rejects valid ones.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
first use differs from index order	`[["v4", "v2", "v3", "v0"], [[0, 1, 2], [2, 1, 3]]]`	`[["v0", "v2", "v3", "v4"], [[3, 1, 2], [2, 1, 0]]]`	Failed

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