trajectory op• データ種: points × signal → table
• 呼び出し: import fullseye as fs; fs.ledger.traj_tau_dot(points, t_s, target=(0.0, 0.0, 0.0), normal=None) (実装を直接呼ぶなら import flyvision; flyvision.traj_tau_dot(points, t_s, target=(0.0, 0.0, 0.0), normal=None)、台帳から引くなら opsflyvision.get("traj_tau_dot"))
実測の 3-D 軌跡に沿った距離・接近速度・τ・τ̇(Lee 1976)。
> 以下の詳細説明は原文のままです —— 要約と見出しは訳出済み。
The quantity a looming detector is supposed to deliver, computed from the true path so that an eye's estimate can be scored against it. With d(t) the distance to *target* (a point, or — with *normal* — the signed distance to the plane through *target*), the approach speed is v = -dd/dt, the time-to-contact tau = d/v and its rate tau-dot = d tau/dt. Lee's (1976) sign convention: tau-dot = -1 at constant speed, tau-dot = -0.5 under the constant deceleration that stops exactly at the target (the braking law), and a value between them means the agent is braking enough to stop short.
points: (N, 3) positions, metres, N >= 3.
t_s: (N,) strictly increasing sample times, seconds.
target: the point approached (3,), metres.
normal: None for the Euclidean distance to *target*, or a (3,) plane
normal: the distance is then (p - target) . normal / |normal|.
Returns a dict {"t_s", "distance_m", "speed_m_s", "tau_s", "tau_dot", "closest_m", "t_closest_s", "n"}. Samples where the agent is not approaching (v <= 0) carry NaN in tau_s and tau_dot — a documented non-finite: a receding agent has no time-to-contact.
Ground truth (pinned in the tests): for d = v0 t toward the target at constant speed tau-dot == -1, and for d = v0 t - a t^2 / 2 with v0^2 = 2 a d0 (stops exactly at the target) tau-dot == -0.5 — both to 1e-9 on a uniform grid, where central differences are exact for a quadratic.
Raises ValueError: *points* not (N, 3) with N >= 3 (an empty *points* is refused), a *t_s* that is not (N,) strictly increasing, non-finite entries, a malformed *target* / *normal*, and a zero *normal*.
• サンプルデータ カタログ(DL URL / ライセンス) — 2-D は skimage.data(BSD/public)+ 合成、3-D は実データ源(Stanford/PDS 等)の DL URL。
• 演算子の来歴・参考文献 — この op 族の元になった研究/手法の出典。
• アルゴリズムの正典(著者・年)と用途は上記ファミリ使い方ガイドに記載。
• poc_zebra_stripes_fly_eye — py -3.11 examples/poc_zebra_stripes_fly_eye.py
table を入力に取れる)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
trajectory)—
*Provenance: flyvision.py — FLYVISION operator registry. この per-op ノートは tools/opdocs.py md が自動生成(手編集しない)。*
© 2026 Kazufumi Furuse — Fullseye operator documentation. Licensed under Apache-2.0.