The field was 20-degree-rotated value noise on a square lattice, three dyadic
octaves at 1 / 0.5 / 0.25 and a sin hash behind it. Value noise prints the
density of the cell's four corners, so every clump sat on a knot of one grid,
and the grid's own repeat — 13 cells, 44px at the 35mm cell — is what the eye
read as diagonal lines. Measured on the old field through the app
(`grain-analog-test.cjs`, `_grain-spectrum.cjs`): off-origin autocorrelation
peak 0.32-0.40, spectral peak/median 29-35, top peaks at 5.4-7.8px.
The field is jittered clumps now, in both copies
(docker/frontend/shared/utils/grainShader.ts and src/utils/grainShader.ts).
A clump lands at a random spot inside its cell — Worley F1 over the 3x3
neighbourhood, `grainClump` — so no two clumps share a grid, and what is
printed is the distance to the nearest: a smooth mound, not one pixel of
static. The hash behind the jitter is sin-free (Hoskins' `p3 = fract(vec3 *
0.1031); p3 += dot(p3, p3.yzx + 33.33)`), because a float sinus whose argument
grows with the picture folds back on itself and is a lattice of its own. The
three octaves are turned to their own angles — 20, 47, 73 degrees — and sit on
0.53 and 0.29 off the dyadic 1 / 0.5 / 0.25, where a coarse octave's cells land
back on the fine one's and stack.
Clumps sit higher and tighter than the value noise they replace — mean 0.569
against 0.500, sigma 0.123 against 0.081, measured — so the sum is put back on
that mean and spread, `n = (n - 0.5685) * 0.52 + 0.5`, before the AMOUNT
knob's own gain. The web keeps its uniforms (cell, seed, per-stock weights,
spread); the phone keeps 0.55/0.30/0.15 and 2.95, which are the web's
classic-chrome row, so the two print the same texture.
Measured on the deployed build: `grain-stock-test.cjs` 53/0 — 35mm still
coarser than 120, the halation chain intact per stock, the "halation follows
the stock" ordering intact, the field still clumped (r1 0.336-0.506) and still
surviving a 2x downscale. `_grain-spectrum.cjs` residual autocorrelation peak
0.02 (was 0.32-0.40), spectral peak/median 7.0-12.7 (was 29-35), top peaks
only at 2-3px periods, the cell scale. `_grain-ck.cjs` at the preview cell
(U=1.481/1.704): rho1 0.093/0.177 against the old 0.505/0.586, acPeak
0.02/0.028 against 0.38/0.467, peak/med 10.1/11.2 against 76/46.5, top peaks
2.0-2.9px against 5.4-7.8px. `grain-size-test.cjs` 12/0.
`grain-analog-test.cjs` 7/0 — with the TEMP pair on AUTO, the field's channel
split measures 0 at a cast of 0, so the grain is exactly monochrome and no
neighbour lag carries structure (max |rho1..8| 0.118).
One honest number: the preview's apparent strength at GRAIN 10 is ~25% higher
than the old field's (sigma 61.3 against 47.9 in that harness), and that is the
PREVIEW, not the field. Step 9 of src/engine/exportEngine.ts sharpens the
preview at alpha 0.5, and the clumps now sit at the cell (~1.7px) instead of on
the old ~5px lattice, so that sharpen bites harder. The field's own composite
spread is 17% UNDER the old one at the same geometry — lab sdRaw 24.9 against
30.0, and geometry-flat where the old one was ~30 everywhere. The 0.52
normalisation was kept rather than re-tuned upward to the app-visible number:
the export path does not carry that sharpen, and a grain tuned to it would
print too strong.
ponytail: the octave angles and the 0.53/0.29 rungs are one working set, not a
search. Re-tune only if a stock's cell is changed again.
Verified: 53/0 + 12/0 + 7/0 grain harnesses, `_grain-spectrum.cjs` and
`_grain-ck.cjs` A/B against the field built from HEAD, `sims-test.cjs` 31/0,
`fx-mono-test.cjs` 15/0, no page errors.
3dtours
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