typed op• Data kinds: points → volume
• Call: fullseye.apply(img, "tb_plane_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_plane_sdf: stages (docs site)
On other images (synthetic scene / photo / coins. Top row: inputs, bottom row: their outputs. Knobs at default):
▸ tb_plane_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 half-space (the side cut off by a plane) (negative inside, positive outside).
sdf(p) = (p - point) · n̂. The side the normal n̂ points to is outside (positive), the opposite side inside. Used for operations that keep only one side, such as chamfering, cutting, or "only above the substrate". Stacking sdf_intersect builds any convex polyhedron. However, intersection by max is not exact outside the corners: building a cuboid from 6 planes, the occupancy (<= 0) and the inside values match box_sdf exactly, but outside it underestimates near the corners by up to 2.1 (measured on a box of half side 2, grid 0.25) —— a standard property of CSG; if the distance itself is needed, use box_sdf.
Exactness: a plane has gradient norm 1 in all of space, so this value is the true signed distance everywhere (no case split that switches at corners as in box_sdf is needed).
Arguments and validation (ValueError):
• grid: float array (..., 3) whose last axis is 3 (output of grid_coords or a point list).
• point: 1 point on the plane (3 elements).
• normal: normal of the plane (3 elements; zero vector and NaN are rejected). Its length is normalised to 1 automatically, so the magnitude does not affect the result (only the direction matters).
Return value: float64 of grid.shape[:-1]. Positive on the normal side, negative on the opposite side, 0 on the plane.
Usage: sdf_subtract(part, plane_sdf(g, p, n)) "cuts away the normal side of that plane". To reverse the direction, flip the sign of normal (-sdf gives the same).
The 3d op plane_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_plane_sdf 0.50 0.50
▸ Load this pipeline · Load & run
The examples below call the underlying ledger op plane_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.