Initial

src/scene/params.js

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+/* ============================================================
+   params.js — derive a full, tasteful parameter set from a seed.
+   This makes the seed the COMPLETE fingerprint of a plate: the
+   same seed always yields the same parameters, so an inspiration
+   thumbnail and its print-resolution master are identical. Pass
+   a seed anywhere and get the same image at any size.
+
+   A seed first selects a weighted "archetype" (overall character)
+   then jitters within it, so the gallery is varied but every
+   plate stays plausible.
+   ============================================================ */
+import { makeRng } from '../rng.js';
+
+const ARCHETYPES = [
+  { name: 'archival', w: 0.42 },
+  { name: 'dense', w: 0.20 },
+  { name: 'cosmic', w: 0.16 },
+  { name: 'clean', w: 0.12 },
+  { name: 'negative', w: 0.10 },
+];
+
+function pickArchetype(rng) {
+  const total = ARCHETYPES.reduce((s, a) => s + a.w, 0);
+  let t = rng() * total;
+  for (const a of ARCHETYPES) { if ((t -= a.w) <= 0) return a.name; }
+  return 'archival';
+}
+
+export function archetypeOf(seed) {
+  return pickArchetype(makeRng(seed, 'params'));
+}
+
+export function paramsFromSeed(seed) {
+  const rng = makeRng(seed, 'params');
+  const arch = pickArchetype(rng);
+  const r = (lo, hi) => lo + (hi - lo) * rng();
+  const ri = (lo, hi) => Math.round(r(lo, hi));
+  const chance = (p) => rng() < p;
+
+  // base (archival) defaults
+  const p = {
+    seed,
+    primaries: ri(12, 24), burst: r(0.55, 0.92), vdecay: ri(2, 6),
+    cosmics: ri(4, 10), sweepers: ri(2, 7),
+    bfield: r(0.8, 1.6), eloss: r(0.45, 0.75), pspread: r(0.6, 0.85),
+    deltaRate: r(0.6, 0.95), deltaTight: r(0.6, 1.0),
+    shock: true, shockIntensity: r(0.6, 0.9), shockSize: r(0.26, 0.4),
+    shockStriations: r(0.45, 0.85), shockY: r(0.4, 0.6), shockX: r(-0.12, 0.12),
+    shockStain: Math.pow(rng(), 1.5),                 // skew cleaner, allow grime
+    instrument: r(0.25, 0.6),
+    bgEvents: ri(3, 8), bgIntensity: r(0.35, 0.5),
+    density: r(1.0, 1.35), size: r(0.9, 1.15),
+    bloom: r(0.4, 0.65), mottle: r(0.4, 0.7), grain: r(0.4, 0.6),
+    vign: r(0.35, 0.6), artifacts: r(0.4, 0.8),
+    showFiducials: chance(0.85), showBoundary: chance(0.7), showHeader: chance(0.9),
+    invert: true,
+  };
+
+  if (arch === 'dense') {
+    Object.assign(p, {
+      primaries: ri(26, 40), burst: r(0.85, 1.0), vdecay: ri(4, 8),
+      cosmics: ri(8, 14), sweepers: ri(5, 9), bfield: r(1.4, 2.4),
+      deltaRate: r(0.85, 1.0), deltaTight: r(0.8, 1.2),
+      bgEvents: ri(7, 11), density: r(1.25, 1.5), shockIntensity: r(0.6, 0.85),
+    });
+  } else if (arch === 'cosmic') {
+    Object.assign(p, {
+      primaries: ri(4, 10), burst: r(0.25, 0.55), vdecay: ri(0, 2),
+      cosmics: ri(10, 16), sweepers: ri(7, 11), bfield: r(0.6, 1.1),
+      pspread: r(0.8, 0.95), deltaRate: r(0.35, 0.6), instrument: r(0.45, 0.7),
+      shock: chance(0.4), shockIntensity: r(0.3, 0.7), bgEvents: ri(2, 5),
+      density: r(0.85, 1.1),
+    });
+  } else if (arch === 'clean') {
+    Object.assign(p, {
+      primaries: ri(8, 14), burst: r(0.4, 0.65), vdecay: ri(1, 3),
+      cosmics: ri(1, 4), sweepers: ri(1, 4), deltaRate: r(0.35, 0.6),
+      deltaTight: r(0.55, 0.8), shock: chance(0.6), shockIntensity: r(0.3, 0.7),
+      shockStain: Math.pow(rng(), 3),                 // mostly clean disk
+      instrument: r(0.1, 0.3), bgEvents: ri(0, 3), bgIntensity: r(0.2, 0.35),
+      bloom: r(0.25, 0.45), mottle: r(0.15, 0.4), grain: r(0.12, 0.35),
+      vign: r(0.2, 0.4), artifacts: r(0.1, 0.4),
+    });
+  } else if (arch === 'negative') {
+    Object.assign(p, { invert: false, vign: r(0.4, 0.6), shockStain: Math.pow(rng(), 1.3) });
+  }
+
+  p.archetype = arch;
+  return p;
+}