alias op• Data kinds: signal × table → table
• Call: import fullseye as fs; fs.ledger.lattice_moire_peak(signal, lattice, fmax_cycles_per_deg=0.0, n_freq=48, window='hann') (to call the implementation directly, import flyvision; flyvision.lattice_moire_peak(signal, lattice, fmax_cycles_per_deg=0.0, n_freq=48, window='hann'); from the registry, opsflyvision.get("lattice_moire_peak"))
How sharp the strongest low-frequency component of a sampled signal is — the moire a lattice makes of a texture it cannot resolve.
Sampling a texture above the lattice's Nyquist limit does not lose it; it folds it to a lower frequency. On a regular lattice the fold is a single sharp peak — a false stripe the next stage reads as a real one — and on an irregular arrangement the same energy spreads into a ring. This op measures that difference as a number: the non-uniform discrete Fourier transform of the ommatidial signal (mean removed, radially windowed) at the gnomonic positions of the ommatidia, over a grid of n_freq x n_freq frequencies up to *fmax_cycles_per_deg* (0 = the lattice's own hexagonal Nyquist 1/(sqrt 3 dphi), the band the eye can represent), and the ratio of the highest amplitude on that grid to the median amplitude.
signal: (n,) ommatidial values (fly_view_plane_texture).
lattice: the eye they were sampled on — any geometry; only directions are used. fmax_cycles_per_deg: the half-width of the frequency grid, cycles/degree.
n_freq: grid side, 8 <= n_freq <= MAX_MOIRE_FREQ.
window: one of MOIRE_WINDOWS — a radial Hann taper over the field
(default: the field edge is a step and would leak everywhere).
Returns a dict {"peak_ratio", "peak_cycles_per_deg", "peak_amplitude", "background_median", "nyquist_cycles_per_deg", "n_freq"}.
Ground truth (pinned in the tests): a sinusoid just below Nyquist sampled on the hexagonal eye gives a peak ratio above 30; the same sinusoid on a Vogel eye of the same count and mean spacing gives a peak ratio at least 2.5x smaller — the energy that was one peak is now a ring.
Raises ValueError: a *signal* that is not (n,) for this lattice (an empty *signal* is refused), non-finite entries, a constant signal (there is no spectrum to rank — its ratio would be 0/0), a negative *fmax*, an *n_freq* outside its range, an unknown *window*, and a malformed *lattice*.
• 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_moire_screen — py -3.11 examples/poc_moire_screen.py
• poc_print_registration — py -3.11 examples/poc_print_registration.py
• poc_zebra_stripes_fly_eye — py -3.11 examples/poc_zebra_stripes_fly_eye.py
table as input)fly_t4t5_field · fly_flow_from_directions · fly_matched_filter · fly_egomotion_from_flow · fly_eye_merge · fly_view_plane_texture · fly_hex_resample · fly_expansion_readout
alias)*Provenance: flyvision.py — FLYVISION 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.