feature op• Data kinds: voxel → voxel
• Call: import fullseye as fs; fs.ledger.vol_gradient_magnitude(vol) (to call the implementation directly, import volops; volops.vol_gradient_magnitude(vol); from the registry, ops3d.get("vol_gradient_magnitude"))
3-D Sobel gradient magnitude sqrt(gz**2 + gy**2 + gx**2).
Each g* is a scipy.ndimage.sobel derivative along one axis. The response localises at intensity boundaries (a step edge lights up on the interface and is ~0 in flat regions). Returns a (D, H, W) float64 volume.
Computation: scipy.ndimage.sobel is applied along axis 0 (z), 1 (y), 2 (x) in that order, and sqrt(gz**2 + gy**2 + gx**2) is returned. Sobel is a separable kernel of derivative [-1,0,1] and smoothing [1,2,1] (4x each on the 2 orthogonal axes), so the response to a unit step (0→1) perpendicular to an axis is not 1 but 16 (16.0 on the 2 voxels straddling the interface, 0 in flat regions; scipy's default weights, boundary mode='reflect'). Values are not normalised (they do not fit in [0, 1]). No spacing is accepted; differences are in voxel units (no per-axis correction even for anisotropic voxels).
Validation (ValueError): not 3-D / contains NaN or Inf / voxel count exceeds MAX_VOXELS (1 << 27).
Where to use: landscape input for vol_watershed, picking interface ridges with vol_local_maxima, normalising to [0, 1] with vol_stretch for display.
• 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.
• vessel_metrology — py -3.11 examples_3d/vessel_metrology.py
voxel as input)voxel_to_mips · voxel_to_mesh · signed_distance_field · to_points · sobel3d · hessian3d · curvature_maps · edt_jfa
feature)sobel3d · hessian3d · curvature_maps · edt_jfa · edt_jfa_vector · vol_frangi · vol_local_std · vol_local_thickness
*Provenance: volops.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.