FAILURE MAP
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FA-88436 / Mesh topology invariants / Open access

Half-edge next pointer assumes triangular faces · case 01

On quads and pentagons the next half-edge points back into the wrong corner.

Verified by executionVariant 1 · 7 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

The successor corner is computed modulo 3 instead of modulo the face size.

THE FAILURE

The successor corner is computed modulo 3 instead of modulo the face size.

Unsuccessful approach: Using the size of the first face fails on mixed polygon meshes.

Case contract

Input [faces, queries]. Build half-edges (f[i], f[i+1 mod n]) with face index, next and prev half-edges. A repeated directed half-edge returns ["duplicate-halfedge", [a,b]]. For each query (a,b) return null if it is not a half-edge, else [face, next, prev, twin] with twin [b,a] when that directed half-edge exists, else null.

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.

1 / The failure

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json
import math
N = 1
observations = []
def solve(x):
    faces,queries=x
    H={}
    for fi,f in enumerate(faces):
        n=len(f)
        for i in range(n):
            h=(f[i],f[(i+1)%n])
            if h in H: return ['duplicate-halfedge',list(h)]
            H[h]=(fi,(f[(i+1)%n],f[(i+2)%3]),(f[(i-1)%n],f[i]))
    out=[]
    for a,b in queries:
        h=(a,b)
        if h not in H:
            out.append(None)
            continue
        fi,nx,pv=H[h]
        tw=[b,a] if (b,a) in H else None
        out.append([fi,list(nx),list(pv),tw])
    return out
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['quad pair', [[[[0, 1, 2, 3], [3, 2, 4, 5]], [[0, 1], [2, 3], [3, 2], [4, 5], [1, 0]]]], [[0, [1, 2], [3, 0], None], [0, [3, 0], [1, 2], [3, 2]], [1, [2, 4], [5, 3], [2, 3]], [1, [5, 3], [2, 4], None], None]], ['triangle pair', [[[[0, 1, 2], [2, 1, 3]], [[1, 2], [2, 1], [3, 2], [0, 1]]]], [[0, [2, 0], [0, 1], [2, 1]], [1, [1, 3], [3, 2], [1, 2]], [1, [2, 1], [1, 3], None], [0, [1, 2], [2, 0], None]]], ['triangle then quad', [[[[0, 1, 2], [2, 1, 3, 4]], [[1, 3], [3, 4], [2, 1], [4, 2]]]], [[1, [3, 4], [2, 1], None], [1, [4, 2], [1, 3], None], [1, [1, 3], [4, 2], [1, 2]], [1, [2, 1], [3, 4], None]]], ['tetrahedron', [[[[0, 2, 1], [0, 1, 3], [1, 2, 3], [0, 3, 2]], [[0, 2], [2, 0], [1, 3], [3, 1]]]], [[0, [2, 1], [1, 0], [2, 0]], [3, [0, 3], [3, 2], [0, 2]], [1, [3, 0], [0, 1], [3, 1]], [2, [1, 2], [2, 3], [1, 3]]]], ['flipped duplicate', [[[[0, 1, 2], [0, 1, 3]], [[0, 1]]]], ['duplicate-halfedge', [0, 1]]], ['pentagon', [[[[0, 1, 2, 3, 4]], [[3, 4], [4, 0], [0, 4]]]], [[0, [4, 0], [2, 3], None], [0, [0, 1], [3, 4], None], None]], ['cube', [[[[0, 3, 2, 1], [4, 5, 6, 7], [0, 1, 5, 4], [1, 2, 6, 5], [2, 3, 7, 6], [3, 0, 4, 7]], [[0, 3], [3, 0], [4, 5], [7, 6]]]], [[0, [3, 2], [1, 0], [3, 0]], [5, [0, 4], [7, 3], [0, 3]], [1, [5, 6], [7, 4], [5, 4]], [4, [6, 2], [3, 7], [6, 7]]]]], [['quad pair', [[[[0, 1, 2, 3], [3, 2, 4, 5]], [[0, 1], [2, 3], [3, 2], [4, 5], [1, 0]]]], [[0, [1, 2], [3, 0], None], [0, [3, 0], [1, 2], [3, 2]], [1, [2, 4], [5, 3], [2, 3]], [1, [5, 3], [2, 4], None], None]], ['triangle pair', [[[[0, 1, 2], [2, 1, 3]], [[1, 2], [2, 1], [3, 2], [0, 1]]]], [[0, [2, 0], [0, 1], [2, 1]], [1, [1, 3], [3, 2], [1, 2]], [1, [2, 1], [1, 3], None], [0, [1, 2], [2, 0], None]]], ['triangle then quad', [[[[0, 1, 2], [2, 1, 3, 4]], [[1, 3], [3, 4], [2, 1], [4, 2]]]], [[1, [3, 4], [2, 1], None], [1, [4, 2], [1, 3], None], [1, [1, 3], [4, 2], [1, 2]], [1, [2, 1], [3, 4], None]]], ['flipped duplicate', [[[[0, 1, 2], [0, 1, 3]], [[0, 1]]]], ['duplicate-halfedge', [0, 1]]], ['pentagon', [[[[0, 1, 2, 3, 4]], [[3, 4], [4, 0], [0, 4]]]], [[0, [4, 0], [2, 3], None], [0, [0, 1], [3, 4], None], None]], ['cube', [[[[0, 3, 2, 1], [4, 5, 6, 7], [0, 1, 5, 4], [1, 2, 6, 5], [2, 3, 7, 6], [3, 0, 4, 7]], [[0, 3], [3, 0], [4, 5], [7, 6]]]], [[0, [3, 2], [1, 0], [3, 0]], [5, [0, 4], [7, 3], [0, 3]], [1, [5, 6], [7, 4], [5, 4]], [4, [6, 2], [3, 7], [6, 7]]]], ['missing queries', [[[[0, 1, 2], [2, 1, 3]], [[0, 3], [3, 0], [2, 0]]]], [None, None, [0, [0, 1], [1, 2], None]]]], [['quad pair', [[[[0, 1, 2, 3], [3, 2, 4, 5]], [[0, 1], [2, 3], [3, 2], [4, 5], [1, 0]]]], [[0, [1, 2], [3, 0], None], [0, [3, 0], [1, 2], [3, 2]], [1, [2, 4], [5, 3], [2, 3]], [1, [5, 3], [2, 4], None], None]], ['triangle pair', [[[[0, 1, 2], [2, 1, 3]], [[1, 2], [2, 1], [3, 2], [0, 1]]]], [[0, [2, 0], [0, 1], [2, 1]], [1, [1, 3], [3, 2], [1, 2]], [1, [2, 1], [1, 3], None], [0, [1, 2], [2, 0], None]]], ['triangle then quad', [[[[0, 1, 2], [2, 1, 3, 4]], [[1, 3], [3, 4], [2, 1], [4, 2]]]], [[1, [3, 4], [2, 1], None], [1, [4, 2], [1, 3], None], [1, [1, 3], [4, 2], [1, 2]], [1, [2, 1], [3, 4], None]]], ['tetrahedron', [[[[0, 2, 1], [0, 1, 3], [1, 2, 3], [0, 3, 2]], [[0, 2], [2, 0], [1, 3], [3, 1]]]], [[0, [2, 1], [1, 0], [2, 0]], [3, [0, 3], [3, 2], [0, 2]], [1, [3, 0], [0, 1], [3, 1]], [2, [1, 2], [2, 3], [1, 3]]]], ['flipped duplicate', [[[[0, 1, 2], [0, 1, 3]], [[0, 1]]]], ['duplicate-halfedge', [0, 1]]], ['pentagon', [[[[0, 1, 2, 3, 4]], [[3, 4], [4, 0], [0, 4]]]], [[0, [4, 0], [2, 3], None], [0, [0, 1], [3, 4], None], None]], ['cube', [[[[0, 3, 2, 1], [4, 5, 6, 7], [0, 1, 5, 4], [1, 2, 6, 5], [2, 3, 7, 6], [3, 0, 4, 7]], [[0, 3], [3, 0], [4, 5], [7, 6]]]], [[0, [3, 2], [1, 0], [3, 0]], [5, [0, 4], [7, 3], [0, 3]], [1, [5, 6], [7, 4], [5, 4]], [4, [6, 2], [3, 7], [6, 7]]]]], [['quad pair', [[[[0, 1, 2, 3], [3, 2, 4, 5]], [[0, 1], [2, 3], [3, 2], [4, 5], [1, 0]]]], [[0, [1, 2], [3, 0], None], [0, [3, 0], [1, 2], [3, 2]], [1, [2, 4], [5, 3], [2, 3]], [1, [5, 3], [2, 4], None], None]], ['triangle pair', [[[[0, 1, 2], [2, 1, 3]], [[1, 2], [2, 1], [3, 2], [0, 1]]]], [[0, [2, 0], [0, 1], [2, 1]], [1, [1, 3], [3, 2], [1, 2]], [1, [2, 1], [1, 3], None], [0, [1, 2], [2, 0], None]]], ['triangle then quad', [[[[0, 1, 2], [2, 1, 3, 4]], [[1, 3], [3, 4], [2, 1], [4, 2]]]], [[1, [3, 4], [2, 1], None], [1, [4, 2], [1, 3], None], [1, [1, 3], [4, 2], [1, 2]], [1, [2, 1], [3, 4], None]]], ['flipped duplicate', [[[[0, 1, 2], [0, 1, 3]], [[0, 1]]]], ['duplicate-halfedge', [0, 1]]], ['pentagon', [[[[0, 1, 2, 3, 4]], [[3, 4], [4, 0], [0, 4]]]], [[0, [4, 0], [2, 3], None], [0, [0, 1], [3, 4], None], None]], ['cube', [[[[0, 3, 2, 1], [4, 5, 6, 7], [0, 1, 5, 4], [1, 2, 6, 5], [2, 3, 7, 6], [3, 0, 4, 7]], [[0, 3], [3, 0], [4, 5], [7, 6]]]], [[0, [3, 2], [1, 0], [3, 0]], [5, [0, 4], [7, 3], [0, 3]], [1, [5, 6], [7, 4], [5, 4]], [4, [6, 2], [3, 7], [6, 7]]]], ['missing queries', [[[[0, 1, 2], [2, 1, 3]], [[0, 3], [3, 0], [2, 0]]]], [None, None, [0, [0, 1], [1, 2], None]]]], [['quad pair', [[[[0, 1, 2, 3], [3, 2, 4, 5]], [[0, 1], [2, 3], [3, 2], [4, 5], [1, 0]]]], [[0, [1, 2], [3, 0], None], [0, [3, 0], [1, 2], [3, 2]], [1, [2, 4], [5, 3], [2, 3]], [1, [5, 3], [2, 4], None], None]], ['triangle pair', [[[[0, 1, 2], [2, 1, 3]], [[1, 2], [2, 1], [3, 2], [0, 1]]]], [[0, [2, 0], [0, 1], [2, 1]], [1, [1, 3], [3, 2], [1, 2]], [1, [2, 1], [1, 3], None], [0, [1, 2], [2, 0], None]]], ['triangle then quad', [[[[0, 1, 2], [2, 1, 3, 4]], [[1, 3], [3, 4], [2, 1], [4, 2]]]], [[1, [3, 4], [2, 1], None], [1, [4, 2], [1, 3], None], [1, [1, 3], [4, 2], [1, 2]], [1, [2, 1], [3, 4], None]]], ['tetrahedron', [[[[0, 2, 1], [0, 1, 3], [1, 2, 3], [0, 3, 2]], [[0, 2], [2, 0], [1, 3], [3, 1]]]], [[0, [2, 1], [1, 0], [2, 0]], [3, [0, 3], [3, 2], [0, 2]], [1, [3, 0], [0, 1], [3, 1]], [2, [1, 2], [2, 3], [1, 3]]]], ['flipped duplicate', [[[[0, 1, 2], [0, 1, 3]], [[0, 1]]]], ['duplicate-halfedge', [0, 1]]], ['pentagon', [[[[0, 1, 2, 3, 4]], [[3, 4], [4, 0], [0, 4]]]], [[0, [4, 0], [2, 3], None], [0, [0, 1], [3, 4], None], None]], ['cube', [[[[0, 3, 2, 1], [4, 5, 6, 7], [0, 1, 5, 4], [1, 2, 6, 5], [2, 3, 7, 6], [3, 0, 4, 7]], [[0, 3], [3, 0], [4, 5], [7, 6]]]], [[0, [3, 2], [1, 0], [3, 0]], [5, [0, 4], [7, 3], [0, 3]], [1, [5, 6], [7, 4], [5, 4]], [4, [6, 2], [3, 7], [6, 7]]]]]]
for label, args, expected in fixtures[N-1]:
    check(label, solve(*args), expected)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
Boundary fixtureActualExpectedOutcome
quad pair[[0, [1, 2], [3, 0], None], [0, [3, 1], [1, 2], [3, 2]], [1, [2, 4], [5, 3], [2, 3]], [1, [5, 2], [2, 4], None], None][[0, [1, 2], [3, 0], None], [0, [3, 0], [1, 2], [3, 2]], [1, [2, 4], [5, 3], [2, 3]], [1, [5, 3], [2, 4], None], None]Failed
triangle pair[[0, [2, 0], [0, 1], [2, 1]], [1, [1, 3], [3, 2], [1, 2]], [1, [2, 1], [1, 3], None], [0, [1, 2], [2, 0], None]][[0, [2, 0], [0, 1], [2, 1]], [1, [1, 3], [3, 2], [1, 2]], [1, [2, 1], [1, 3], None], [0, [1, 2], [2, 0], None]]Passed
triangle then quad[[1, [3, 2], [2, 1], None], [1, [4, 1], [1, 3], None], [1, [1, 3], [4, 2], [1, 2]], [1, [2, 3], [3, 4], None]][[1, [3, 4], [2, 1], None], [1, [4, 2], [1, 3], None], [1, [1, 3], [4, 2], [1, 2]], [1, [2, 1], [3, 4], None]]Failed
tetrahedron[[0, [2, 1], [1, 0], [2, 0]], [3, [0, 3], [3, 2], [0, 2]], [1, [3, 0], [0, 1], [3, 1]], [2, [1, 2], [2, 3], [1, 3]]][[0, [2, 1], [1, 0], [2, 0]], [3, [0, 3], [3, 2], [0, 2]], [1, [3, 0], [0, 1], [3, 1]], [2, [1, 2], [2, 3], [1, 3]]]Passed
flipped duplicate['duplicate-halfedge', [0, 1]]['duplicate-halfedge', [0, 1]]Passed
pentagon[[0, [4, 2], [2, 3], None], [0, [0, 0], [3, 4], None], None][[0, [4, 0], [2, 3], None], [0, [0, 1], [3, 4], None], None]Failed
cube[[0, [3, 2], [1, 0], [3, 0]], [5, [0, 4], [7, 3], [0, 3]], [1, [5, 6], [7, 4], [5, 4]], [4, [6, 3], [3, 7], [6, 7]]][[0, [3, 2], [1, 0], [3, 0]], [5, [0, 4], [7, 3], [0, 3]], [1, [5, 6], [7, 4], [5, 4]], [4, [6, 2], [3, 7], [6, 7]]]Failed

SHA-256 / dd28a49893f89de7ad94ac3f0a1e48fa2c2349bb8c6f213619688e6e5e618f8c

2 / The unsuccessful fix

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json
import math
N = 1
observations = []
def solve(x):
    faces,queries=x
    H={}
    for fi,f in enumerate(faces):
        n=len(f)
        for i in range(n):
            h=(f[i],f[(i+1)%n])
            if h in H: return ['duplicate-halfedge',list(h)]
            H[h]=(fi,(f[(i+1)%n],f[(i+2)%len(faces[0])]),(f[(i-1)%n],f[i]))
    out=[]
    for a,b in queries:
        h=(a,b)
        if h not in H:
            out.append(None)
            continue
        fi,nx,pv=H[h]
        tw=[b,a] if (b,a) in H else None
        out.append([fi,list(nx),list(pv),tw])
    return out
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['quad pair', [[[[0, 1, 2, 3], [3, 2, 4, 5]], [[0, 1], [2, 3], [3, 2], [4, 5], [1, 0]]]], [[0, [1, 2], [3, 0], None], [0, [3, 0], [1, 2], [3, 2]], [1, [2, 4], [5, 3], [2, 3]], [1, [5, 3], [2, 4], None], None]], ['triangle pair', [[[[0, 1, 2], [2, 1, 3]], [[1, 2], [2, 1], [3, 2], [0, 1]]]], [[0, [2, 0], [0, 1], [2, 1]], [1, [1, 3], [3, 2], [1, 2]], [1, [2, 1], [1, 3], None], [0, [1, 2], [2, 0], None]]], ['triangle then quad', [[[[0, 1, 2], [2, 1, 3, 4]], [[1, 3], [3, 4], [2, 1], [4, 2]]]], [[1, [3, 4], [2, 1], None], [1, [4, 2], [1, 3], None], [1, [1, 3], [4, 2], [1, 2]], [1, [2, 1], [3, 4], None]]], ['tetrahedron', [[[[0, 2, 1], [0, 1, 3], [1, 2, 3], [0, 3, 2]], [[0, 2], [2, 0], [1, 3], [3, 1]]]], [[0, [2, 1], [1, 0], [2, 0]], [3, [0, 3], [3, 2], [0, 2]], [1, [3, 0], [0, 1], [3, 1]], [2, [1, 2], [2, 3], [1, 3]]]], ['flipped duplicate', [[[[0, 1, 2], [0, 1, 3]], [[0, 1]]]], ['duplicate-halfedge', [0, 1]]], ['pentagon', [[[[0, 1, 2, 3, 4]], [[3, 4], [4, 0], [0, 4]]]], [[0, [4, 0], [2, 3], None], [0, [0, 1], [3, 4], None], None]], ['cube', [[[[0, 3, 2, 1], [4, 5, 6, 7], [0, 1, 5, 4], [1, 2, 6, 5], [2, 3, 7, 6], [3, 0, 4, 7]], [[0, 3], [3, 0], [4, 5], [7, 6]]]], [[0, [3, 2], [1, 0], [3, 0]], [5, [0, 4], [7, 3], [0, 3]], [1, [5, 6], [7, 4], [5, 4]], [4, [6, 2], [3, 7], [6, 7]]]]], [['quad pair', [[[[0, 1, 2, 3], [3, 2, 4, 5]], [[0, 1], [2, 3], [3, 2], [4, 5], [1, 0]]]], [[0, [1, 2], [3, 0], None], [0, [3, 0], [1, 2], [3, 2]], [1, [2, 4], [5, 3], [2, 3]], [1, [5, 3], [2, 4], None], None]], ['triangle pair', [[[[0, 1, 2], [2, 1, 3]], [[1, 2], [2, 1], [3, 2], [0, 1]]]], [[0, [2, 0], [0, 1], [2, 1]], [1, [1, 3], [3, 2], [1, 2]], [1, [2, 1], [1, 3], None], [0, [1, 2], [2, 0], None]]], ['triangle then quad', [[[[0, 1, 2], [2, 1, 3, 4]], [[1, 3], [3, 4], [2, 1], [4, 2]]]], [[1, [3, 4], [2, 1], None], [1, [4, 2], [1, 3], None], [1, [1, 3], [4, 2], [1, 2]], [1, [2, 1], [3, 4], None]]], ['flipped duplicate', [[[[0, 1, 2], [0, 1, 3]], [[0, 1]]]], ['duplicate-halfedge', [0, 1]]], ['pentagon', [[[[0, 1, 2, 3, 4]], [[3, 4], [4, 0], [0, 4]]]], [[0, [4, 0], [2, 3], None], [0, [0, 1], [3, 4], None], None]], ['cube', [[[[0, 3, 2, 1], [4, 5, 6, 7], [0, 1, 5, 4], [1, 2, 6, 5], [2, 3, 7, 6], [3, 0, 4, 7]], [[0, 3], [3, 0], [4, 5], [7, 6]]]], [[0, [3, 2], [1, 0], [3, 0]], [5, [0, 4], [7, 3], [0, 3]], [1, [5, 6], [7, 4], [5, 4]], [4, [6, 2], [3, 7], [6, 7]]]], ['missing queries', [[[[0, 1, 2], [2, 1, 3]], [[0, 3], [3, 0], [2, 0]]]], [None, None, [0, [0, 1], [1, 2], None]]]], [['quad pair', [[[[0, 1, 2, 3], [3, 2, 4, 5]], [[0, 1], [2, 3], [3, 2], [4, 5], [1, 0]]]], [[0, [1, 2], [3, 0], None], [0, [3, 0], [1, 2], [3, 2]], [1, [2, 4], [5, 3], [2, 3]], [1, [5, 3], [2, 4], None], None]], ['triangle pair', [[[[0, 1, 2], [2, 1, 3]], [[1, 2], [2, 1], [3, 2], [0, 1]]]], [[0, [2, 0], [0, 1], [2, 1]], [1, [1, 3], [3, 2], [1, 2]], [1, [2, 1], [1, 3], None], [0, [1, 2], [2, 0], None]]], ['triangle then quad', [[[[0, 1, 2], [2, 1, 3, 4]], [[1, 3], [3, 4], [2, 1], [4, 2]]]], [[1, [3, 4], [2, 1], None], [1, [4, 2], [1, 3], None], [1, [1, 3], [4, 2], [1, 2]], [1, [2, 1], [3, 4], None]]], ['tetrahedron', [[[[0, 2, 1], [0, 1, 3], [1, 2, 3], [0, 3, 2]], [[0, 2], [2, 0], [1, 3], [3, 1]]]], [[0, [2, 1], [1, 0], [2, 0]], [3, [0, 3], [3, 2], [0, 2]], [1, [3, 0], [0, 1], [3, 1]], [2, [1, 2], [2, 3], [1, 3]]]], ['flipped duplicate', [[[[0, 1, 2], [0, 1, 3]], [[0, 1]]]], ['duplicate-halfedge', [0, 1]]], ['pentagon', [[[[0, 1, 2, 3, 4]], [[3, 4], [4, 0], [0, 4]]]], [[0, [4, 0], [2, 3], None], [0, [0, 1], [3, 4], None], None]], ['cube', [[[[0, 3, 2, 1], [4, 5, 6, 7], [0, 1, 5, 4], [1, 2, 6, 5], [2, 3, 7, 6], [3, 0, 4, 7]], [[0, 3], [3, 0], [4, 5], [7, 6]]]], [[0, [3, 2], [1, 0], [3, 0]], [5, [0, 4], [7, 3], [0, 3]], [1, [5, 6], [7, 4], [5, 4]], [4, [6, 2], [3, 7], [6, 7]]]]], [['quad pair', [[[[0, 1, 2, 3], [3, 2, 4, 5]], [[0, 1], [2, 3], [3, 2], [4, 5], [1, 0]]]], [[0, [1, 2], [3, 0], None], [0, [3, 0], [1, 2], [3, 2]], [1, [2, 4], [5, 3], [2, 3]], [1, [5, 3], [2, 4], None], None]], ['triangle pair', [[[[0, 1, 2], [2, 1, 3]], [[1, 2], [2, 1], [3, 2], [0, 1]]]], [[0, [2, 0], [0, 1], [2, 1]], [1, [1, 3], [3, 2], [1, 2]], [1, [2, 1], [1, 3], None], [0, [1, 2], [2, 0], None]]], ['triangle then quad', [[[[0, 1, 2], [2, 1, 3, 4]], [[1, 3], [3, 4], [2, 1], [4, 2]]]], [[1, [3, 4], [2, 1], None], [1, [4, 2], [1, 3], None], [1, [1, 3], [4, 2], [1, 2]], [1, [2, 1], [3, 4], None]]], ['flipped duplicate', [[[[0, 1, 2], [0, 1, 3]], [[0, 1]]]], ['duplicate-halfedge', [0, 1]]], ['pentagon', [[[[0, 1, 2, 3, 4]], [[3, 4], [4, 0], [0, 4]]]], [[0, [4, 0], [2, 3], None], [0, [0, 1], [3, 4], None], None]], ['cube', [[[[0, 3, 2, 1], [4, 5, 6, 7], [0, 1, 5, 4], [1, 2, 6, 5], [2, 3, 7, 6], [3, 0, 4, 7]], [[0, 3], [3, 0], [4, 5], [7, 6]]]], [[0, [3, 2], [1, 0], [3, 0]], [5, [0, 4], [7, 3], [0, 3]], [1, [5, 6], [7, 4], [5, 4]], [4, [6, 2], [3, 7], [6, 7]]]], ['missing queries', [[[[0, 1, 2], [2, 1, 3]], [[0, 3], [3, 0], [2, 0]]]], [None, None, [0, [0, 1], [1, 2], None]]]], [['quad pair', [[[[0, 1, 2, 3], [3, 2, 4, 5]], [[0, 1], [2, 3], [3, 2], [4, 5], [1, 0]]]], [[0, [1, 2], [3, 0], None], [0, [3, 0], [1, 2], [3, 2]], [1, [2, 4], [5, 3], [2, 3]], [1, [5, 3], [2, 4], None], None]], ['triangle pair', [[[[0, 1, 2], [2, 1, 3]], [[1, 2], [2, 1], [3, 2], [0, 1]]]], [[0, [2, 0], [0, 1], [2, 1]], [1, [1, 3], [3, 2], [1, 2]], [1, [2, 1], [1, 3], None], [0, [1, 2], [2, 0], None]]], ['triangle then quad', [[[[0, 1, 2], [2, 1, 3, 4]], [[1, 3], [3, 4], [2, 1], [4, 2]]]], [[1, [3, 4], [2, 1], None], [1, [4, 2], [1, 3], None], [1, [1, 3], [4, 2], [1, 2]], [1, [2, 1], [3, 4], None]]], ['tetrahedron', [[[[0, 2, 1], [0, 1, 3], [1, 2, 3], [0, 3, 2]], [[0, 2], [2, 0], [1, 3], [3, 1]]]], [[0, [2, 1], [1, 0], [2, 0]], [3, [0, 3], [3, 2], [0, 2]], [1, [3, 0], [0, 1], [3, 1]], [2, [1, 2], [2, 3], [1, 3]]]], ['flipped duplicate', [[[[0, 1, 2], [0, 1, 3]], [[0, 1]]]], ['duplicate-halfedge', [0, 1]]], ['pentagon', [[[[0, 1, 2, 3, 4]], [[3, 4], [4, 0], [0, 4]]]], [[0, [4, 0], [2, 3], None], [0, [0, 1], [3, 4], None], None]], ['cube', [[[[0, 3, 2, 1], [4, 5, 6, 7], [0, 1, 5, 4], [1, 2, 6, 5], [2, 3, 7, 6], [3, 0, 4, 7]], [[0, 3], [3, 0], [4, 5], [7, 6]]]], [[0, [3, 2], [1, 0], [3, 0]], [5, [0, 4], [7, 3], [0, 3]], [1, [5, 6], [7, 4], [5, 4]], [4, [6, 2], [3, 7], [6, 7]]]]]]
for label, args, expected in fixtures[N-1]:
    check(label, solve(*args), expected)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
Boundary fixtureActualExpectedOutcome
quad pair[[0, [1, 2], [3, 0], None], [0, [3, 0], [1, 2], [3, 2]], [1, [2, 4], [5, 3], [2, 3]], [1, [5, 3], [2, 4], None], None][[0, [1, 2], [3, 0], None], [0, [3, 0], [1, 2], [3, 2]], [1, [2, 4], [5, 3], [2, 3]], [1, [5, 3], [2, 4], None], None]Passed
triangle pair[[0, [2, 0], [0, 1], [2, 1]], [1, [1, 3], [3, 2], [1, 2]], [1, [2, 1], [1, 3], None], [0, [1, 2], [2, 0], None]][[0, [2, 0], [0, 1], [2, 1]], [1, [1, 3], [3, 2], [1, 2]], [1, [2, 1], [1, 3], None], [0, [1, 2], [2, 0], None]]Passed
triangle then quad[[1, [3, 2], [2, 1], None], [1, [4, 1], [1, 3], None], [1, [1, 3], [4, 2], [1, 2]], [1, [2, 3], [3, 4], None]][[1, [3, 4], [2, 1], None], [1, [4, 2], [1, 3], None], [1, [1, 3], [4, 2], [1, 2]], [1, [2, 1], [3, 4], None]]Failed
tetrahedron[[0, [2, 1], [1, 0], [2, 0]], [3, [0, 3], [3, 2], [0, 2]], [1, [3, 0], [0, 1], [3, 1]], [2, [1, 2], [2, 3], [1, 3]]][[0, [2, 1], [1, 0], [2, 0]], [3, [0, 3], [3, 2], [0, 2]], [1, [3, 0], [0, 1], [3, 1]], [2, [1, 2], [2, 3], [1, 3]]]Passed
flipped duplicate['duplicate-halfedge', [0, 1]]['duplicate-halfedge', [0, 1]]Passed
pentagon[[0, [4, 0], [2, 3], None], [0, [0, 1], [3, 4], None], None][[0, [4, 0], [2, 3], None], [0, [0, 1], [3, 4], None], None]Passed
cube[[0, [3, 2], [1, 0], [3, 0]], [5, [0, 4], [7, 3], [0, 3]], [1, [5, 6], [7, 4], [5, 4]], [4, [6, 2], [3, 7], [6, 7]]][[0, [3, 2], [1, 0], [3, 0]], [5, [0, 4], [7, 3], [0, 3]], [1, [5, 6], [7, 4], [5, 4]], [4, [6, 2], [3, 7], [6, 7]]]Passed

SHA-256 / 9b53fb36f1e17b97bd1364b41f94f969eb5f2371ae8513c3af9e81a846dabb07

HELD IN THE MEMBER ARCHIVE

The verified repair and its recorded checks are member-only.

This mechanism has 7 recorded checks per implementation. The open-access tier publishes the failure and the unsuccessful fix; the repaired source that passes every check, and the observations that prove it, are available to members.

Every case sharing this mechanism uses the same contract and the same repair, so this one record is held back for all of them.

Member access is invitation-based. Sign in with your invited account to inspect the repair.

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Verification & scope

Pure combinatorial teaching model over integer face lists with a stipulated contract; no geometry kernel or file format is implied. This reproducer isolates one failure mechanism. Results cover the supplied fixtures. Variants within a family share a test contract and should remain grouped when constructing evaluation splits. Related mechanisms with a shared evaluation_group must also remain together; these controlled models are not independent production incidents.

Observations recorded using Python 3.12.14 at 2026-09-29T14:51:08.131373+00:00.

Case digest / 55ef6fe4c30a4293795b00926c4a22aaec0a27df6adbc8b66940a7d60eceb95d