curve op• Data kinds: points → measurement
• Call: import fullseye as fs; fs.ledger.arc_length(curve) (to call the implementation directly, import curve3d; curve3d.arc_length(curve); from the registry, ops3d.get("arc_length"))
• Return value through the ledger: fullseye.ledger.arc_length(...) returns only the declared out type measurement (the underlying function also returns auxiliary values). When you need what was dropped, use fullseye.ledger.arc_length.raw(...) or call curve3d.arc_length directly.
• Underlying return: (cumulative, total) → 全長 float
The cumulative arc length of a curve and its total. → (cumulative (N,), total float).
Treats the ordered point sequence curve (N,3) as a polyline in index order and accumulates the Euclidean distances between adjacent points. cumulative[0]=0, cumulative[i] = polyline length from the start up to the i-th point, total = cumulative[-1]. The unit is the same as the coordinates.
• The input is only converted to float; there is no shape validation (the computation goes through even if the column count is not 3).
• For N=1, cumulative=[0.0] and total=0.0. Even for a closed curve the end→start segment is not counted (to close it, duplicate the first point at the end before passing it in).
• Duplicate points (segments of distance 0) are accumulated as 0 as they are, so cumulative is monotonically non-decreasing but not strictly increasing.
resample_uniform interpolates linearly with this cumulative arc length as the parameter. The ds used when combining with curvature_torsion, e.g. for arc-length integrals of curvature, is taken from these differences.
• 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.
• space_curve — py -3.11 examples_3d/space_curve.py
• torus_knot_curve — py -3.11 examples_3d/torus_knot_curve.py
measurement as input)vol_gaussian_psf · fuse_to_voxel · fresnel_reflectance · snell_angle
curve)curvature_torsion · frenet_frame · resample_uniform · fit_spline_curve
*Provenance: curve3d.py — 3D 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.