FA-88753 / Mesh topology invariants / Member archive

UV seam test compares edge UVs in traversal order · case 03

Every interior edge is reported as a seam because neighbours traverse it in opposite directions.

Member previewVariant 3 · 3 implementations · 7 checks per implementation

Case contract

Input [faces, uvfaces]: each face has a parallel list of UV indices. A face whose UV list length differs returns ["uv-mismatch", face index]. A geometric edge is a seam when a later face assigns a different UV index to either endpoint than the first face did. Return sorted seam edges [min,max].

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
shared uv no seam	`[[1, 2]]`	`[]`	Failed

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