typed op• Data kinds: points → volume
• Call: fullseye.apply(img, "tb_sphere_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_sphere_sdf: stages (docs site)
On other images (synthetic scene / photo / coins. Top row: inputs, bottom row: their outputs. Knobs at default):
▸ tb_sphere_sdf: other inputs (docs site)
Motion (GIF: frames / views / slices in turn. The still figure is the complete one; the GIF is supplementary):
Signed distance field of a sphere: |p - center| - R (negative inside, positive outside).
grid is a coordinate array whose last axis is 3, (..., 3) (output of grid_coords or an (N,3) point cloud). center has length 3, R>=0 is the radius. The returned shape is grid.shape[:-1]. An exact SDF (gradient norm 1). sdf_offset(sphere_sdf(g,c,R), r) == sphere_sdf(g,c,R+r).
R < 0 or a malformed grid / center raises ValueError.
Computation: np.linalg.norm(grid - center, axis=-1) - R. The coordinate unit becomes the distance unit as is (pass world coordinates from grid_coords and you get world units). The component order of the coordinates is the order of grid's last axis ((x, y, z) for grid_coords), and center uses the same order.
Arguments and validation (ValueError):
• grid: float array (..., 3) whose last axis is 3 (a 1-D (3,) is also allowed; 0-D or a last axis other than 3 is rejected).
• center: 3 elements (if it cannot be reshape(3), numpy's ValueError).
• R: a scalar that float() accepts. Passing a rotation matrix or the like also gives ValueError (this argument is a radius, not a pose). R < 0 is rejected; R = 0 is the distance field from the centre itself.
Return value: float64 of grid.shape[:-1] ((nx, ny, nz) for output of grid_coords). -R at the centre, 0 on the surface, positive outside.
Usage: grid from grid_coords → sphere_sdf / box_sdf → CSG with sdf_union / sdf_subtract → marching cubes with <= 0 as occupied (pass -sdf to voxel_to_mesh for the isosurface equivalent to iso=0).
The 3d op sphere_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_sphere_sdf 0.50 0.50
▸ Load this pipeline · Load & run
The examples below call the underlying ledger op sphere_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).
• annotate3d_figure — py -3.11 examples_3d/annotate3d_figure.py
• gear_metrology — py -3.11 examples_3d/gear_metrology.py
• molecule_atom_count — py -3.11 examples_3d/molecule_atom_count.py
• procedural_hand — py -3.11 examples_3d/procedural_hand.py
• render_beauty — py -3.11 examples_3d/render_beauty.py
• sdf_csg — py -3.11 examples_3d/sdf_csg.py
• sfm_recon — py -3.11 examples_3d/sfm_recon.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.