angle_defect — MATH geometry op

• Data kinds: mesh → table

• Call: import fullseye as fs; fs.ledger.angle_defect(vertices, faces=None) -> 'dict' (to call the implementation directly, import mathgeometry; mathgeometry.angle_defect(vertices, faces=None) -> 'dict'; from the registry, opsmath.get("angle_defect"))

Usage

> This operator's description has not been translated yet. The original text follows as it is.

頂点ごとの角欠損(離散 Gauss 曲率)K_v = 2π − Σ(その頂点での三角形の角)。境界の頂点は π − Σ(測地曲率)。

閉じたメッシュでは Σ K_v = 2πχ が厳密に成り立つ(Descartes の定理)。境界があるときは

Σ(内部の K) + Σ(境界の π − Σθ) = 2πχ(離散 Gauss–Bonnet)。

返り値 `{"defect", "total", "two_pi_chi", "is_boundary"}`。

Family-wide input contract (fail-closed)

Every mathops op validates its input before computing (nothing slips through silently):

• **complex input raises ValueError** — coercing to float64 silently discards the imaginary part (numpy only emits a ComplexWarning and returns a plausible-looking wrong real number). State .real/.imag/abs() explicitly, or use complexops, which handles complex data.

• **masked arrays with masked elements raise ValueError** — the implicit conversion that peels off the mask and uses the raw values underneath is refused. Say explicitly whether to fill or to drop.

• **NaN/Inf raises ValueError on every input** (refused with the count stated — it propagates through the whole result).

• Shapes are strict: 1-D and 2-D are never implicitly promoted or broadcast (a matrix in a vector slot, or a vector in a matrix slot, raises ValueError; reshape explicitly).

• Size cap: ops that take a matrix, and the stat_histogram bins, raise ValueError beyond mathops.MAX_ELEMENTS (2^26 ≈ 67 million elements).

Detailed usage guide

• math_metrology family guide

References (sample data, literature)

• Sample-data catalog (download URLs / licences) — 2-D uses skimage.data (BSD/public domain) plus synthetic images; 3-D lists download URLs for real data sources (Stanford, PDS, …).

• Operator provenance and references — the sources of the research/methods this op family came from.

• The canonical algorithm (author, year) and its uses are named in the family usage guide above.

Runnable examples (verified samples that actually call this op)

• geometry_tour — py -3.11 examples/geometry_tour.py

Ops the type connects to (they accept table as input)

dynsys_poincare_section · dwt_inverse · chebyshev_eval_nd

Same category (geometry)

mesh_euler_characteristic · delaunay_triangulate · geodesic_heat · geodesic_heat_grid · mesh_torus · nurbs_curve · nurbs_circle · nurbs_surface


*Provenance: mathgeometry.py — MATH operator registry. This per-op note is generated by tools/opdocs.py md (do not hand-edit).*

© 2026 Kazufumi Furuse — Fullseye operator documentation. Licensed under Apache-2.0.