{
  "id": "section9-rectangle-grid-v1",
  "description": "Six unit squares with consistently oriented northeast diagonals; two interior vertices.",
  "points": [[0,0],[1,0],[2,0],[3,0],[0,1],[1,1],[2,1],[3,1],[0,2],[1,2],[2,2],[3,2]],
  "triangles": [[0,1,5],[0,5,4],[1,2,6],[1,6,5],[2,3,7],[2,7,6],[4,5,9],[4,9,8],[5,6,10],[5,10,9],[6,7,11],[6,11,10]],
  "interior_vertices": [5,6],
  "boundary_vertices": [0,1,2,3,4,7,8,9,10,11],
  "off_origin_parameters": [0.05,-0.03],
  "conventions": {
    "curvature": -1,
    "angle_units": "radians",
    "corner_order": "vertex order in each oriented triangle",
    "deformation": "angle at a in (a,b,c) changes by u_b-u_c; boundary u=0",
    "volume": "sum of ideal tetrahedral volumes obtained by adjoining infinity; binary64 evaluation",
    "boundary_voltage": "x/3, independent of the angle-deformation parameter u",
    "delaunay_scope": "non-strict: each square diagonal has zero cotangent weight",
    "certificate_scope": "exact rational finite matrix/forest identities for this fixture; no strict polyhedral realization certificate"
  }
}