light: the SHADOW knob rides half its anchor, so a lift stops drawing the band above it flat — a waterfall's spray came back at 0.10 of its own contrast, 0.55 now
This commit is contained in:
@@ -16,13 +16,15 @@
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// THE TONE PASS builds the luma a new ramp instead. The four knobs
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// (HIGHLIGHT, SHADOW, WHITE, BLACK) are the four zones of the tone-mapping doc —
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// one tent each, one per quarter of the ramp — and each knob moves the knot it
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// owns by TONE_ANCHOR of the ramp, held inside the knot before it. The 0.50
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// midpoint is the one value all four leave where it was.
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// owns by TONE_ANCHOR of the ramp, held inside the knot before it; SHADOW, whose
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// knot is the head of the band above it rather than an end of the ramp, moves
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// half that. The 0.50 midpoint is the one value all four leave where it was.
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//
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// Both are SkSL, so the SHAPE is pinned on the source; the arithmetic is then
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// checked against the source's own constants, and the ramp re-run here as a twin
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// so monotonicity, the neutral identity and the partition of the four masks are
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// checked rather than asserted in a comment.
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// so monotonicity, the neutral identity, the partition of the four masks and the
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// slope SHADOW leaves the band above it are checked rather than asserted in a
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// comment.
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//
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// node scripts/highlight-knee-check.mjs
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import assert from 'node:assert/strict';
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@@ -83,7 +85,7 @@ assert.match(sksl, /float hlMask = clamp\(smoothstep\(0\.50, 0\.75, t\) - whMask
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// knots next to them.
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assert.match(sksl, /float a4 = 1\.0 \+ 0\.25 \* wh - dr \* 0\.18;/);
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assert.match(sksl, /float a3 = clamp\(0\.75 \+ 0\.25 \* hl - dr \* 0\.09, 0\.5, a4\);/);
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assert.match(sksl, /float a1 = clamp\(0\.25 \+ 0\.25 \* sh \+ dr \* 0\.06, 0\.0, 0\.5\);/);
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assert.match(sksl, /float a1 = clamp\(0\.25 \+ 0\.25 \* 0\.5 \* sh \+ dr \* 0\.06, 0\.0, 0\.5\);/);
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assert.match(sksl, /float a0 = clamp\(0\.25 \* bl \+ dr \* 0\.12, 0\.0, a1\);/);
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assert.doesNotMatch(sksl, /o \+= dr \* 0\.12/, 'DR is an additive term again — it folds the flat stretch at 0.238');
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// Straight between the knots, and NOT a smoothstep: an S-curve through the
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@@ -173,7 +175,7 @@ function ramp(t, k) {
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const hlMask = clamp01(smoothstep(0.5, 0.75, t) - whMask);
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const a4 = 1 + A * wh - dr * 0.18;
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const a3 = Math.min(a4, Math.max(0.5, 0.75 + A * hl - dr * 0.09));
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const a1 = Math.min(0.5, Math.max(0, 0.25 + A * sh + dr * 0.06));
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const a1 = Math.min(0.5, Math.max(0, 0.25 + A * 0.5 * sh + dr * 0.06));
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const a0 = Math.min(a1, Math.max(0, A * bl + dr * 0.12));
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let o = mix(a0, a1, lin(0, 0.25, t));
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o = mix(o, mix(a1, 0.5, lin(0.25, 0.5, t)), step(0.25, t));
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@@ -235,12 +237,15 @@ for (const k of combos) {
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}
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assert.ok(worst > -1e-12, `worst step ${worst} — the ramp is folded`);
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// A knob moves its own quarter, and only its own: +BLACK takes the toe off the
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// floor, +SHADOW puts the 0.25 knot on the midpoint, -HIGHLIGHT pulls the 0.75
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// knot onto it, and WHITE - rolls the head under 1.0. That is the reach a
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// tonal-range slider has — a quarter of the ramp, so the middle stays a middle.
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// floor, -HIGHLIGHT pulls the 0.75 knot onto the midpoint, and WHITE - rolls the
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// head under 1.0. That is the reach a tonal-range slider has — a quarter of the
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// ramp, so the middle stays a middle. SHADOW is the exception and moves HALF of
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// it: its knot is the HEAD of the 0.25..0.50 band, so a whole quarter would draw
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// that band flat, which is the wash-out the knob was reported for.
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close(ramp(0, {}).o, 0, 'a neutral toe moved');
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close(ramp(0, { bl: 1 }).o, A, 'BLACK no longer reaches a quarter of the ramp');
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close(ramp(0.25, { sh: 1 }).o, 0.5, 'SHADOW no longer reaches the midpoint');
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close(ramp(0.25, { sh: 1 }).o, 0.375, 'SHADOW no longer stops halfway to the midpoint');
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close(ramp(0.25, { sh: -1 }).o, 0.125, 'SHADOW no longer stops halfway to the floor');
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close(ramp(0.75, { hl: -1 }).o, 0.5, 'HIGHLIGHT no longer reaches the midpoint');
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close(ramp(1, { wh: -1 }).o, 0.75, 'WHITE no longer rolls the head under 1.0');
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close(ramp(0.25, {}).o, 0.25, 'a neutral knot moved');
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@@ -259,11 +264,48 @@ close(ramp(1, { dr: 1 }).o, 0.82, 'DR no longer rolls the head the way it did');
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close(ramp(0.5, { dr: 1 }).o, 0.5, 'DR moved the midpoint');
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// Black and shadow both at -1 are the flat stretch DR used to fold: the toe is
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// held on the floor by the ordering clamp (BLACK's -0.25 cancels DR's +0.12),
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// the 0.25 knot is DR's own +0.06, and the stretch between them is a straight
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// line up to the midpoint — never a step down.
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// the 0.25 knot is DR's own +0.06 over SHADOW's half-anchor -0.125, and the
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// stretch between them is a straight line up to the midpoint — never a step
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// down.
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assert.equal(ramp(0, { dr: 1, bl: -1, sh: -1 }).o, 0);
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assert.equal(ramp(0.25, { dr: 1, bl: -1, sh: -1 }).o, 0.06);
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close(ramp(0.375, { dr: 1, bl: -1, sh: -1 }).o, 0.28, 'DR folded the flat stretch');
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assert.equal(ramp(0.25, { dr: 1, bl: -1, sh: -1 }).o, 0.185);
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close(ramp(0.375, { dr: 1, bl: -1, sh: -1 }).o, 0.3425, 'DR folded the flat stretch');
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// The band above SHADOW is the one that pays for its lift, and HALF its slope is
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// the floor the fix is. Measured on a real frame (DSCF1701, 21% of its pixels in
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// that band) with SHADOW +90, a whole anchor left 0.10 of the band's own spread
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// where half leaves 0.55 — see the note on a1 in toneShader.ts and the sweep in
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// scratchpad sh-band.mjs. Swept here over the knob's whole travel: neither
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// quarter of the ramp SHADOW touches may be drawn flatter than half its slope,
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// and neither may be stretched past one and a half, which is the same defect
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// upside down (a crush that flattens the darks into one black).
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for (let sh = -1; sh <= 1.0001; sh += 1 / 64) {
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const below = (ramp(0.25, { sh }).o - ramp(0, { sh }).o) / 0.25;
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const band = (ramp(0.5, { sh }).o - ramp(0.25, { sh }).o) / 0.25;
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assert.ok(band >= 0.5 - 1e-12, `SHADOW drew the band above it flat at ${sh}: slope ${band}`);
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assert.ok(below >= 0.5 - 1e-12, `SHADOW drew the quarter below it flat at ${sh}: slope ${below}`);
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assert.ok(band <= 1.5 + 1e-12, `SHADOW stretched the band above it at ${sh}: slope ${band}`);
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}
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// The film stocks ride the same knot, so a halved SHADOW would have halved their
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// crush with it. They are written at DOUBLE for that reason, and the look they
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// were tuned to is the knot, not the unit: these three land where they always
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// did (0.18 Classic Chrome/Vivid, 0.22 Acros, 0.17 Acros HC).
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const filmTone = tone.match(/const FILM_TONE[\s\S]*?\n};/)?.[0];
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assert.ok(filmTone, 'FILM_TONE is gone — the stocks no longer shape the ramp at all');
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// The keys are quoted or not depending on whether they are identifiers, so the
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// quotes come off before the lookup.
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const filmFlat = filmTone.replace(/['"]/g, '');
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for (const [name, sh, knot] of [
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['classic-chrome', -0.56, 0.18],
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['classic-vivid', -0.56, 0.18],
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['monochrome', -0.24, 0.22],
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['mono-high-contrast', -0.64, 0.17],
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]) {
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assert.ok(
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filmFlat.includes(`${name}: { sh: ${sh}`),
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`${name} is not on the doubled ${sh} — the stock's crush moved with the knob's reach`
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);
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close(ramp(0.25, { sh }).o, knot, `${name}'s shadow knot moved`);
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}
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// The two ends stay ordered even at full deflection against each other: the toe
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// can never climb past the head.
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for (const bl of [-1, 1])
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@@ -32,7 +32,11 @@ import { HSL_BANDS, hslBandGaps, isMonochromeBase } from './colorUtils';
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// measurement is monotone for every combination of the four at full deflection.
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// A knob moves its anchor by a quarter of the ramp, so +10 BLACKS puts the toe
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// on 0.25 and -10 WHITES rolls the head down to 0.75: the reach a tonal range
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// slider has in the program this layout copies, without the inversion.
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// slider has in the program this layout copies, without the inversion. SHADOW is
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// the one knob held to half of that, because the knot it moves is the HEAD of
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// the quarter above it and not an end of the ramp: a band cannot be lifted at
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// its head and keep its slope at the same time, so the knob's travel is what has
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// to give — see the measured note on a1.
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//
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// WHITE and BLACK are not the per-channel toe and shoulder they were on the WB
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// tab any more. The doc puts the two points on the ends of the SAME ramp as the
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@@ -103,9 +107,12 @@ const BAND_BLOCK = hslBandGaps()
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// How far a tonal-range knob moves its own knot, in ramp units. A quarter is
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// the reach the program this layout copies gives a slider: at full deflection
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// the four together can put the toe on the midpoint, the head on it, or either
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// end on the quarter next to it — and never past, because each knot is clamped
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// inside the one before it.
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// the toe can reach the quarter above it and the head can be rolled onto it —
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// and never past, because each knot is clamped inside the one after it.
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//
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// SHADOW is the one knob that moves HALF of it. The knot it owns is the HEAD of
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// the 0.25..0.50 quarter, so a unit of lift is a unit of slope that quarter
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// loses, and at a whole quarter the band is drawn flat — see the note on a1.
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export const TONE_ANCHOR = 0.25;
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// The tone and exposure maths, in ONE copy, because two passes ask it: the
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@@ -125,8 +132,9 @@ float lin(float e0, float e1, float x) {
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return clamp((x - e0) / (e1 - e0), 0.0, 1.0);
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}
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// The ramp the pixel is rebuilt through. Knots on 0.00, 0.25, 0.50, 0.75 and
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// 1.00; a knob moves the knot it owns by TONE_ANCHOR of the ramp, and each knot
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// is held inside the one before it so the five can never cross. 0.50 is fixed:
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// 1.00; a knob moves the knot it owns by TONE_ANCHOR of the ramp — SHADOW by
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// half of that, its knot being the head of a band — and each knot is held inside
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// the one after it so the five can never cross. 0.50 is fixed:
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// it is the one point all four sliders leave alone, which is what keeps a
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// mid-grey a mid-grey while the ends move around it. Straight between the knots,
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// so every knob on zero is exactly the identity (see the note at the head of
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@@ -186,7 +194,19 @@ vec3 lightMove(vec3 c, float t, float o) {
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vec3 toneRamp(vec3 c, float t, float bl, float sh, float hl, float wh, float dr) {
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float a4 = 1.0 + ${TONE_ANCHOR} * wh - dr * 0.18;
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float a3 = clamp(0.75 + ${TONE_ANCHOR} * hl - dr * 0.09, 0.5, a4);
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float a1 = clamp(0.25 + ${TONE_ANCHOR} * sh + dr * 0.06, 0.0, 0.5);
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// SHADOW rides HALF the anchor, and that is a measured ceiling rather than a
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// taste. a1 is the HEAD of the quarter above it, so the band 0.25..0.50 pays
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// in slope for every unit this knot rises — the slope is (0.5 - a1) / 0.25 —
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// and that band is where a waterfall's spray and a sunlit rock sit. At the
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// whole anchor the knot lands ON the midpoint and draws the band flat: on a
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// real frame (DSCF1701, misty valley, 21% of its pixels in the band) SHADOW
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// +90 came back with 0.10 of the band's own spread and a mean of 0.392 where
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// it was 0.489 — the milky white sheet the knob was reported for, bright areas
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// with their contrast gone. At half: 0.55 of the spread, mean 0.441, and the
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// toe still opens at 1.45x. Half also keeps the knob smooth over its whole
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// travel — a clamp alone would pin it from +50 on and leave the top of the
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// slider dead — which is why the RATE is halved and not just the ceiling.
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float a1 = clamp(0.25 + ${TONE_ANCHOR} * 0.5 * sh + dr * 0.06, 0.0, 0.5);
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float a0 = clamp(${TONE_ANCHOR} * bl + dr * 0.12, 0.0, a1);
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float o = mix(a0, a1, lin(0.00, 0.25, t));
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o = mix(o, mix(a1, 0.5, lin(0.25, 0.50, t)), step(0.25, t));
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@@ -638,11 +658,17 @@ export interface ToneUniforms {
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// Chrome crushes the shadows hard while muting colour. Those two parts live
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// here instead of in the 4x5 matrix, which cannot move one end of the curve
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// without also moving the other.
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//
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// The `sh` here is written at DOUBLE what the knob's own arithmetic reads, which
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// is not a taste either: SHADOW moves its knot half an anchor per unit (see a1
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// in TONE_MATH_SKSL), so a stock that wants the toe on 0.18 has to ask for -0.56
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// to land it there. The stock's crush is the knot it puts the ramp on; the unit
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// it is written in belongs to the knob, not to the look.
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const FILM_TONE: Partial<Record<BaseFilter, Partial<ToneUniforms>>> = {
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'classic-chrome': { sh: -0.28 },
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'classic-chrome': { sh: -0.56 },
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// Classic Vivid is Classic Chrome's sibling — the shadow crush belongs to the
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// stock, not to the matrix rows, so it comes along.
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'classic-vivid': { sh: -0.28 },
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'classic-vivid': { sh: -0.56 },
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'classic-neg': { shT: [-0.018, 0.009, 0.013], hlT: [0.024, 0.008, -0.012] },
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// Acros. A black-and-white stock IS its grey ramp, so this entry only shapes
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// the two ENDS and leaves the middle an identity: a smooth shadow toe that
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@@ -651,18 +677,19 @@ const FILM_TONE: Partial<Record<BaseFilter, Partial<ToneUniforms>>> = {
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// paper. Mid-tones are between the 0.25 and the 0.75 knots, so they keep
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// every step the matrix handed over — which is what 'deep black' costs in a
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// colour stock and does not have to cost here.
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// The values move the two end knots of the ramp: -0.12 puts the toe on 0.22
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// and -0.05 rolls the head to 0.7375 (each is TONE_ANCHOR = 0.25 per unit).
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monochrome: { sh: -0.12, hl: -0.05 },
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// The values move the two end knots of the ramp: -0.24 puts the toe on 0.22
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// and -0.05 rolls the head to 0.7375 (HIGHLIGHT is TONE_ANCHOR per unit, the
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// doubled SHADOW half of it).
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monochrome: { sh: -0.24, hl: -0.05 },
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// B&W HIGH CONTRAST. Acros' ramp with both ends pushed hard: a deeper toe
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// (-0.32 against Acros' -0.12, so 0.17 against 0.22) so the darks reach true
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// (-0.64 against Acros' -0.24, so 0.17 against 0.22) so the darks reach true
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// black, and a shoulder that LIFTS instead of rolling (-0.05 → +0.26, the
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// head going to 0.815), which is the whites step of the brief. The stretch
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// between the two inner knots (0.25 and 0.75) is still the identity, so the
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// long smooth stretch of the greys survives — that is what keeps a hard push
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// off the posterised look, and the strength the stock needs on the greys is
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// its matrix slope (SIM_CONTRAST_BIAS in colorUtils), not another move here.
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'mono-high-contrast': { sh: -0.32, hl: 0.26 },
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'mono-high-contrast': { sh: -0.64, hl: 0.26 },
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};
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export function getToneUniforms(adj: ColorAdjustments, baseFilter?: BaseFilter): ToneUniforms {
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Reference in New Issue
Block a user