vol_affine — 3D geom_transform op

• Data kinds: voxel → voxel

• Call: import fullseye as fs; fs.ledger.vol_affine(vol, matrix, offset=(0, 0, 0), order=1, output_shape=None, mode='constant', cval=0.0) (to call the implementation directly, import volxform; volxform.vol_affine(vol, matrix, offset=(0, 0, 0), order=1, output_shape=None, mode='constant', cval=0.0); from the registry, ops3d.get("vol_affine"))

Usage

General affine resampling (scipy.ndimage.affine_transform).

Convention (pinned — read this before writing a matrix): this is scipy's pull (output -> input) resampler. For every output voxel at integer coordinate o = (z, y, x) the result is the input interpolated at matrix @ o + offset::

out[o] = vol[ matrix @ o + offset ] # (z, y, x) order, voxels

Consequences: matrix = 2*I makes the object appear half size (each output step strides two input voxels); offset = (1, 2, 3) moves the object by (-1, -2, -3). To *push* content through a forward transform T (the pose from a registration), pass the inverse of T. The test suite machine-pins this direction.

*matrix* is either a (3, 3) linear part (with *offset* a separate length-3 translation) or a (4, 4) homogeneous matrix [[A, t], [0, 0, 0, 1]] — then A / t are taken from the matrix, the bottom row must be exactly (0, 0, 0, 1), and *offset* must stay at its zero default (a second translation would be ambiguous). Any other shape raises ValueError.

*output_shape* defaults to the input shape; an explicit one is cap-checked against MAX_VOXELS before allocation. *order* is the spline degree (exact integer 0..5). Voxels whose source coordinate falls outside the input are filled per *mode*/*cval*.

Returns a float64 volume of *output_shape*.

References (sample data, literature)

• 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.

Runnable examples (verified samples that actually call this op)

• vol_geometry_transform — py -3.11 examples_3d/vol_geometry_transform.py

Ops the type connects to (they accept voxel as input)

voxel_to_mips · voxel_to_mesh · signed_distance_field · to_points · sobel3d · hessian3d · curvature_maps · edt_jfa

Same category (geom_transform)

vol_resize · vol_rotate

*Provenance: volxform.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.