polarization op• Data kinds: polsweep → image2d
• Call: import fullseye as fs; fs.ledger.polarization_separate(images, angles_deg=(0.0, 45.0, 90.0, 135.0), max_violation_frac=0.0) (to call the implementation directly, import specularity; specularity.polarization_separate(images, angles_deg=(0.0, 45.0, 90.0, 135.0), max_violation_frac=0.0); from the registry, opsspecular.get("polarization_separate"))
• Return value through the ledger: fullseye.ledger.polarization_separate(...) returns only the declared out type image2d (the underlying function also returns auxiliary values). When you need what was dropped, use fullseye.ledger.polarization_separate.raw(...) or call specularity.polarization_separate directly.
Split a polariser sweep into its unpolarised and linearly polarised radiance. → (diffuse, specular), both (H, W).
Fitting I(t) = 0.5 (S0 + S1 cos 2t + S2 sin 2t) per pixel gives I_min and I_max in closed form, and the classical separation (Wolff & Boult 1991; Nayar, Fang & Boult 1997) reads
diffuse = 2 * I_min (the unpolarised radiance)
specular = I_max - I_min (the linearly polarised radiance)
with diffuse + specular = I_min + I_max = the total scene radiance, so nothing is lost or invented. Round-tripping polarization_render through this operator returns the inputs with a maximum absolute error of 3.9e-16 for the four angles of a division-of-focal-plane sensor and 4.4e-16 for a bare three-angle sweep (measured in tests/test_specularity.py).
Read the names as shorthand. What is recovered exactly is the unpolarised and polarised parts. Calling them diffuse and specular assumes diffuse reflection is unpolarised and specular reflection is fully linearly polarised — true near Brewster's angle for a dielectric, false at normal incidence, where the specular reflection is unpolarised and this operator returns all of it as "diffuse", and unreliable for metals. The polarisation route is complementary to the colour route (specular_diffuse_split), not a replacement: it needs no illuminant colour and works on textured, multi-material surfaces, but it needs a favourable geometry.
*max_violation_frac* is the fraction of pixels allowed to fit a negative minimum radiance before the call fails. The default 0 is fail-closed: a negative fitted minimum means the modulation exceeded the mean, which no analyser can produce, and it usually means the frames and *angles_deg* are out of order. Raise it to clamp sensor-noise-level violations to zero as a deliberate, recorded choice.
Raises ValueError: *images* is not an (N, H, W) stack of at least 3 frames, or exceeds MAX_LIGHTS / MAX_STACK_ELEMENTS; *angles_deg* does not match the frame count or leaves the fit rank-deficient (two angles equal modulo 180); more than *max_violation_frac* of the pixels fit a negative minimum.
• specular_photometric family guide
• 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.
• poc_polarization_specular — py -3.11 examples/poc_polarization_specular.py
• specular_photometric — py -3.11 examples/specular_photometric.py
image2d as input)polarization)polarization_render · polarization_dolp_map · polarization_stokes
*Provenance: specularity.py — SPECULAR 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.