typed op• Data kinds: points → feature
• Call: fullseye.apply(img, "tb_arc_length", a=0.5, b=0.5) (the 2-D model is one image plus two scalar knobs a,b∈[0,1])
*The figure is the actual output on a synthetic 128×128 input. Left: input, right: output. Point clouds are drawn as a top-down scatter (brightness = z), 1-D series as a line plot, volumes as the maximum-intensity projection along z, videos as the middle frame, complex images as magnitude; return values that are not pictures are shown as the values themselves.*
*Knob a does not change the output (measured: identical at 0.1 / 0.5 / 0.9).*
*Knob b does not change the output (measured: identical at 0.1 / 0.5 / 0.9).*
Stages (the ops that come before → this op, left to right):
▸ tb_arc_length: stages (docs site)
Cumulative arc length and total length of a curve. → (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]. Units are the same as the coordinates.
• The input is merely converted to float; there is no shape check (the computation goes through even if the number of columns 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, 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.
The 3d op arc_length bridged into the 2-D evolution registry. The implementation is the same; only the calling convention is adapted to op(v, a, b). This op has no tuning points; neither a nor b is used.
• 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 program below has been verified to run (same input as the figure). In Studio's help this block becomes buttons that load and run it on the spot.
img_to_points 0.50 0.50 tb_arc_length 0.50 0.50
▸ Load this pipeline · Load & run
The examples below call the underlying ledger op arc_length. This bridge op is the same implementation adapted to the fn(v, a, b) convention, so the behaviour carries over unchanged (only the call form differs).
• space_curve — py -3.11 examples_3d/space_curve.py
• torus_knot_curve — py -3.11 examples_3d/torus_knot_curve.py
feature as input)typed)tb_points_to_voxel · tb_estimate_point_normals · tb_iss_keypoints · tb_project_points · tb_render_point_depth · tb_statistical_outlier_removal · tb_radius_outlier_removal · tb_voxel_grid_downsample
*Provenance: ops.py — 2D 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.