tac_surface_normal — 2D tactile op

Data kinds: imageimage

Call: fullseye.apply(img, "tac_surface_normal", a=0.5, b=0.5) (the 2-D model is one image plus two scalar knobs a,b∈[0,1])

Usage

Surface-normal z-component (slope map) from the shading gradients, using Horn's shape-from-shading normal parameterisation `n = (-p, -q, 1)/sqrt(1+p^2+q^2) so that nz = 1/sqrt(1+p^2+q^2) with p = gain*gx, q = gain*gy. Flat (uncontacted) gel gives nz = 1, steep indentation walls tend to 0, so the map is already a valid [0,1] encoding. a = gradient gain (1..21x -- how steep the shading is taken to be), b` = pre-smoothing sigma of the image (0..3) to tame sensor noise. Constant input -> all-ones (perfectly flat gel).

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)

sim2real_and_alifepy -3.11 examples/sim2real_and_alife.py

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

identity · gaussian · mean_box · bilateral · unsharp · median · min_filter · max_filter

Same category (tactile)

tac_contact_mask · tac_height_from_shading · tac_pressure_proxy · tac_shear_field


*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.