tactile op• Data kinds: image → image
• Call: fullseye.apply(img, "tac_shear_field", 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.*
Sweeping knob a (0.1 / 0.5 / 0.9, the other knob at its default):
▸ tac_shear_field: knob a sweep (docs site)
Sweeping knob b (0.1 / 0.5 / 0.9, the other knob at its default):
▸ tac_shear_field: knob b sweep (docs site)
On other images (synthetic scene / photo / coins. Top row: inputs, bottom row: their outputs. Knobs at default):
▸ tac_shear_field: other inputs (docs site)
*The 4th column is a colour (H,W,3) input. This op handles colour without crossing channels (it does not convolve the colour channel as a third spatial axis).*
In-plane shear proxy from the 2-D structure tensor (Foerstner / Bigun-Granlund orientation coherence). The tensor `J = G_sigma(grad v * grad v^T) has eigenvalues l1 >= l2, and the coherence (l1-l2)/(l1+l2) = sqrt((J11-J22)^2 + 4*J12^2) / (J11+J22) is 1 where the gel texture is stretched into a single dominant orientation (as it is under tangential/shear load) and 0 where it is isotropic. The result is additionally weighted by the tensor trace (gradient energy) so that texture-free, un-contacted gel stays dark instead of amplifying noise orientation. a = tensor integration sigma (0.6..4.6), b` = output gain (0.5..2.5). Output clipped to [0,1], HxW; a constant frame has zero gradient energy and yields an all-zero shear field.
Blank frame (measured): feeding an image of uniform brightness gives an empty result — every pixel is background (0) — regardless of the brightness. Pure white and pure black behave alike; brightness by itself detects nothing.
• 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.
tac_shear_field 0.50 0.50
▸ Load this pipeline · Load & run
• sim2real_and_alife — py -3.11 examples/sim2real_and_alife.py
image as input)identity · gaussian · mean_box · bilateral · unsharp · median · min_filter · max_filter
tactile)tac_contact_mask · tac_height_from_shading · tac_surface_normal · tac_pressure_proxy
*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.