e2e5104646
Forty-nine scenes carried their own `glow`, every one of the sixty-five added its own grain, and a handful had bloom, chroma, haze, smear or trail besides — all of which the post chain already does, with an envelope and a threshold no scene can see. Two uncoordinated effect layers is the smaller half of the problem. The larger half is that an effect knob sampled per song makes a scene look varied across parameter draws while its structure never moves, so the gallery and the variety harness were both being told a scene was original when only its halo had changed. Removed in three shapes. Scene grain goes entirely — the post chain owns it. Statements that ADD a falloff term scaled by the effect are bloom by another name and are deleted. What remains is an intensity on something already drawn, so the uniform is pinned to its default and the knob deleted: the picture survives, the fake variety does not. Reactive entries driving those params went too, since an effect modulated by the audio was the most convincing fake of the lot. That broke the style trait, which is the interesting part. Surface treatment had been leaving the scenes for two commits — sigGrain to post, sigEdge to inkStroke — and removing the last of it left `style` with almost nothing to express: a style+shape signature had two eligible scenes in the whole library. The trait is not obsolete, it has moved, so inkStroke and inkMask now read u_sigLine and u_sigSoft alongside the ink's own weight and edge. A scene drawing in the song's hand honours the track's line weight by construction, and the runtime probe confirms it rather than taking it on trust. This reverses a call made two commits ago for a reason that only became true now. One check needed re-aiming rather than fixing. Two independently built shows are two WebGL contexts, and engine/hash.js says at the top that bit-exactness is a same-context guarantee; the check had been demanding it anyway and getting away with it because the scenes it happened to cast were bit-stable. A casting change put smooth-gradient scenes in frame and the last bit moved. Measured before touching the check: three levels out of 255 across 2.6% of pixels, invisible. The cross-context comparison is now a distance with a ceiling of four, and bit-exactness within one show is still demanded by the check below it. 89/89 checks, 11/11 tests, all static gates. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
103 lines
4.6 KiB
JavaScript
103 lines
4.6 KiB
JavaScript
// Structural family: a suspension bridge passing overhead — two towers in
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// frame at a time, the main cable slung between them, hangers dropping to a
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// deck that runs off both sides.
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//
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// Girder Lattice is a truss: hundreds of short members in tension and
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// compression, and the image is a texture of triangles. This is the opposite
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// structure and reads as one — two long curves and a rhythm of verticals under
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// them, with almost nothing else in the frame. The curve is the whole subject,
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// and the only thing that repeats is the spacing.
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export const suspensionSpan = {
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name: 'Suspension Span',
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family: 'structural',
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kind: 'fragment',
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texture: 0.6,
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consumes: ['cast', 'ink'],
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traits: ['shape', 'camera', 'space', 'style'],
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params: {
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span: { type: 'float', range: [0.5, 2.2], default: 1.1, uniform: 'u_span', bias: 'density' },
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sag: { type: 'float', range: [0.15, 0.9], default: 0.5, uniform: 'u_sag' },
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tower: { type: 'float', range: [0.3, 1.1], default: 0.7, uniform: 'u_tower' },
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hangers: { type: 'float', range: [2, 22], default: 9, uniform: 'u_hangers', bias: 'density' },
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deck: { type: 'float', range: [-0.7, 0.25], default: -0.2, uniform: 'u_deck', slowAxis: true },
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lamp: { type: 'float', range: [0, 0.12], default: 0.045, uniform: 'u_lamp' },
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travel: { type: 'float', range: [0.01, 0.3], default: 0.06, uniform: 'u_travel', bias: 'motion', rate: true },
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palette: { type: 'palette', count: 5 },
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},
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reactive: {
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lamp: { feature: 'beat', amount: 0.2, response: 'spike' },
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},
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shader: `
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// Distance to a segment, for the one-off members that are not on a grid.
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float seg(vec2 q, vec2 a, vec2 b) {
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vec2 ab = b - a, ap = q - a;
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float h = sat(dot(ap, ab) / max(dot(ab, ab), 1e-6));
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return length(ap - ab * h);
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}
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vec4 scene(vec2 uv, vec2 p) {
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float t = u_time * u_travel + u_seed;
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p = sigCamera(p);
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float horizon = sigHorizonY() * 0.3;
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float deckY = horizon + u_deck;
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// Sky, and the water or ground under the deck.
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vec3 col = mix(pal(1) * 0.2, pal(0) * 0.06, sat((p.y - horizon) * 0.6 + 0.25));
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col += pal(3) * exp(-abs(p.y - horizon) * 7.0) * 0.2;
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col = mix(col, pal(0) * 0.09, smoothstep(deckY + 0.01, deckY - 0.03, p.y));
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// Bays: the bridge repeats every span, and travelling means the whole
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// structure slides through that repeat.
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float g = (p.x + t) / u_span;
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float bay = fract(g) - 0.5;
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float bayId = floor(g);
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float x = bay * u_span; // metres from this bay's centre
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float towerTop = deckY + u_tower;
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float w = 0.006 + u_sigLine * 0.02;
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// Main cable: a parabola from tower top to tower top, lowest mid-bay.
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float cableY = towerTop - u_sag * u_tower * (1.0 - 4.0 * bay * bay);
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float dCable = abs(p.y - cableY);
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col += palRamp(0.15) * smoothstep(w * 1.6, w * 0.3, dCable) * (0.6 + 0.55 * 0.6);
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// Hangers: verticals from the cable down to the deck, on their own spacing.
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float hg = (p.x + t) * u_hangers / u_span;
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float hx = (fract(hg) - 0.5) * u_span / u_hangers;
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float hangerCableY = towerTop - u_sag * u_tower *
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(1.0 - 4.0 * pow(fract(g + (floor(hg) - hg + 0.5) / u_hangers) - 0.5, 2.0));
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float inSpan = step(p.y, hangerCableY) * step(deckY, p.y);
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col += palRamp(0.3) * smoothstep(w, w * 0.25, abs(hx)) * inSpan * (0.3 + 0.55 * 0.35);
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// Deck: one heavy line all the way across, which is what stops the cable
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// reading as a piece of string.
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col += pal(4) * smoothstep(w * 2.5, w * 0.6, abs(p.y - deckY)) * (0.4 + 0.55 * 0.5);
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col += pal(4) * inkStroke(abs(p.y - deckY) - w * 3.0) * 0.25;
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// Towers: a pair of legs and a crossbeam, with the signature form as the
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// lamp on top — the only object in the frame that is not a line.
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float dTower = min(seg(vec2(x, p.y), vec2(0.0, deckY - 0.1), vec2(0.0, towerTop)),
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seg(vec2(x, p.y), vec2(-0.03, towerTop - 0.12), vec2(0.03, towerTop - 0.12)));
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col += palRamp(0.05) * smoothstep(w * 3.0, w * 1.2, dTower) * 0.7;
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if (u_lamp > 0.004) {
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float d = castMain((vec2(x, p.y) - vec2(0.0, towerTop + u_lamp)) / u_lamp) * u_lamp;
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col += pal(3) * smoothstep(0.004, -0.004, d) * (0.6 + 0.55);
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col += pal(3) * inkStroke(d) * 0.6;
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}
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// Every other bay is a little further off, so the line of the bridge has
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// some air in it rather than being a flat elevation drawing.
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col = sigAir(col, p, smoothstep(0.2, 1.4, abs(bay) * 0.7 + hash11(bayId) * 0.5));
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return vec4(inkValue(col), 1.0);
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}
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`,
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};
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export default suspensionSpan;
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