finish op• Data kinds: none → normalmap (an op determined by its arguments alone — it takes no image or data input)
• Call: import metalfinish; metalfinish.tangent_field(shape, kind='linear', angle_deg=0.0, center=None) -> 'np.ndarray' (or opsoptics.get("tangent_field"))
Build the direction of the lay as a tangent field of (H, W, 3).
> The detailed description below is the original text — the summary and the headings are translated.
shape: (H, W)。kind: FINISHES のいずれか。
angle_deg: linear / crosshatch の筋の向き [deg] (画像座標、+x から反時計回り)。
center: circular / radial の中心 (row, col)。既定は画像中心。
返り値: (H, W, 3) の単位接線場(z 成分 0 = 面内)。random は画素ごとに
向きを散らす(無方向 = ビーズブラスト)。
★ 定ベクトルではなく場なのが要点: 旋盤の削り目は同心円なので、
一定方向の接線ではハイライトが物理的に成立しない。
Every optics op validates its input before computing (nothing slips through silently):
• Units are baked into the argument name — _mm / _um / _deg / _mrad. Confusing mm with µm does not crash; it yields a plausible-looking wrong answer, so the name prevents it. Nothing here guesses the unit from the magnitude.
• **Strings raise ValueError** — float('50') succeeds, so an unparsed configuration value would slip through as a length (measured: thin_lens('50', '200') returned a plausible 66.667 mm). bool is refused too, as the implicit promotion True == 1.
• **complex / masked arrays raise ValueError (real-valued slots only; silently dropping the imaginary part or peeling off the mask is refused). NaN/Inf raises ValueError on every input.**
• Division by zero and its relatives are refused by name: focal length 0, radius of curvature 0, refractive index <= 0, a fully opaque aperture (all zeros, so the normalisation is 0/0), a PSF whose sum is <= 0, a Stokes vector with S0 = 0, and an object sitting at the front focal point (the image is at infinity).
• Only two ops return a non-finite value, and both state it as a contract: depth_of_field returns far_mm = inf beyond the hyperfocal distance (that is what the hyperfocal distance means), and gaussian_beam returns wavefront_radius_mm = inf at the waist (the radius of curvature of a plane wavefront). Both also return a finite companion (far_is_infinite / curvature_per_mm). **Any other silent NaN/Inf is detected internally and raises ValueError** — "float64 overflowed" and "the answer is infinite" are different claims, so the first is never returned wearing the face of the second.
• Size caps: generated grids are capped by optics.MAX_GRID (4096); supplied fields/PSFs/apertures by optics.MAX_FIELD_ELEMENTS (2^24); ABCD element chains by optics.MAX_SYSTEM_ELEMENTS (1024); Zernike by MAX_ZERNIKE_TERMS (512) / MAX_ZERNIKE_ORDER (40) / MAX_ZERNIKE_BASIS (2^25). This closes, fail-closed, the paths where a small argument triggers a huge internal allocation (measured: n_max=40 × 4096² needs 108 GB).
• Physically impossible states are refused too: a Stokes vector with degree of polarisation > 1, negative transmittance, negative intensity, and invalid Zernike indices such as n-|m| odd.
• 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.
• machined_metal_and_materials — py -3.11 examples/machined_metal_and_materials.py
normalmap as input)grating_rgb · thin_film_rgb · ward_anisotropic · micro_normals · blast_normals · finish_shade · oren_nayar · clearcoat_shade
finish)finish_catalog · micro_normals · blast_normals · finish_shade
*Provenance: metalfinish.py — OPTICS 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.