typed op• Data kinds: points → volume
• Call: fullseye.apply(img, "tb_cylinder_sdf", 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_cylinder_sdf: stages (docs site)
On other images (synthetic scene / photo / coins. Top row: inputs, bottom row: their outputs. Knobs at default):
▸ tb_cylinder_sdf: other inputs (docs site)
Motion (GIF: frames / views / slices in turn. The still figure is the complete one; the GIF is supplementary):
Exact signed distance field of a finite-length cylinder (flat caps at both ends) (negative inside, positive outside).
Split into the axial distance t and the radius r from the axis; with q = (r - radius, |t| - height/2), outside = ‖max(q, 0)‖, inside = min(max(q), 0), sdf = outside + inside. This applies the same Quilez-style construction as box_sdf to the "2-D cross-section of (radius, axis)", and gives the true Euclidean distance to the side, the caps and the corners (rims) alike.
Arguments and validation (ValueError):
• grid: float array (..., 3) whose last axis is 3.
• center: the centre of the cylinder (the centroid, not an end face; 3 elements).
• axis: axis direction (3 elements; zero vector and NaN are rejected; length is normalised automatically).
• radius: scalar radius, nominally > 0 (0 is the axis line itself; negative is rejected).
• height: scalar total length (±height/2 from center; negative is rejected).
Return value: float64 of grid.shape[:-1].
Usage: a through hole is sdf_subtract(part, cylinder_sdf(...)) (make height longer than the part so no rim of the end faces remains). Bosses, pins and shafts use sdf_union. If an infinitely long cylinder is needed, make height large enough (once the end faces are outside the evaluated region, only the side matters).
The 3d op cylinder_sdf 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 tunable parameters; 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_cylinder_sdf 0.50 0.50
▸ Load this pipeline · Load & run
The examples below call the underlying ledger op cylinder_sdf. 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).
• sdf_csg — py -3.11 examples_3d/sdf_csg.py
volume as input)identity · vol_gaussian · vol_median · vol_erode · vol_dilate · vol_threshold · vol_reg_dilate · vol_reg_erode
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.