Initial

src/scene/scene.js

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+/* ============================================================
+   scene.js — the single source of truth.
+   generateScene(params) returns a pure, renderer-agnostic data
+   model. Every renderer (photographic raster, vector SVG/PDF)
+   consumes exactly this. Deterministic from params.seed.
+   ============================================================ */
+import { makeRng, gauss, chance, pick } from '../rng.js';
+import { integrateTrack, sampleMomentum, cosmicTrack, sweeperTrack } from './track.js';
+import { spawnDeltaSpiral } from './delta.js';
+import { spawnVDecay } from './vdecay.js';
+import { generateShock } from './shock.js';
+import { generateArtifacts } from './artifacts.js';
+import { generateInstrument } from './instrument.js';
+import { cyrb53 } from '../rng.js';
+
+const LABS = ['BEBC · CERN', 'GARGAMELLE · CERN', '2m HBC · CERN', '82" HBC · SLAC', 'MIRABELLE · IHEP'];
+
+/* One event: a vertex with primaries (+ δ-rays, V-decays for bright events). */
+function generateOneEvent(params, vertex, intensity, salt) {
+  const rng = makeRng(params.seed, 'event:' + salt);
+  const tracks = [];
+  const N = Math.max(2, Math.round(params.primaries * (0.45 + intensity * 0.55)));
+  const burstConc = 0.3 + params.burst * 0.7;
+  const bright = intensity > 0.6;
+
+  for (let i = 0; i < N; i++) {
+    const baseAngle = (i / N) * Math.PI * 2;
+    const angle = baseAngle + gauss(rng) * 0.4 * (1 - burstConc);
+    const p = sampleMomentum(rng, params.pspread);
+    const q = chance(rng, 0.5) ? +1 : -1;
+    const pts = integrateTrack(
+      { x: vertex.x, y: vertex.y, theta: angle, p, q }, params
+    );
+    tracks.push({ pts, kind: 'primary', weight: intensity });
+
+    // δ-rays along bright primaries — abundant, true spirals
+    if (bright) {
+      const dRng = makeRng(params.seed, salt + ':delta' + i);
+      for (let j = 6; j < pts.length; j += 2) {
+        if (dRng() < params.deltaRate * 0.12) {
+          const dpts = spawnDeltaSpiral(pts[j], params, dRng);
+          if (dpts.length > 6) {
+            tracks.push({ pts: dpts, kind: 'delta', weight: intensity * 0.9 });
+          }
+        }
+      }
+    }
+  }
+
+  // dense interaction "star": stubby tracks bursting from the vertex, with a
+  // few medium prongs reaching further out for a richer burst.
+  if (bright && params.burst > 0.15) {
+    const sRng = makeRng(params.seed, salt + ':star');
+    const nStar = Math.floor(params.burst * 26);
+    for (let i = 0; i < nStar; i++) {
+      const a = sRng() * Math.PI * 2;
+      const medium = sRng() < 0.25;
+      const p = medium ? (0.5 + sRng() * 0.7) : (0.13 + sRng() * 0.4);
+      const q = chance(sRng, 0.5) ? 1 : -1;
+      const pts = integrateTrack(
+        { x: vertex.x + gauss(sRng) * 0.012, y: vertex.y + gauss(sRng) * 0.012, theta: a, p, q },
+        params, { maxTravel: medium ? 2.6 : 1.1 }
+      );
+      tracks.push({ pts, kind: 'primary', weight: intensity });
+    }
+  }
+
+  // V-decays only for the brightest (foreground) events
+  if (intensity > 0.8) {
+    for (let i = 0; i < params.vdecay; i++) {
+      const daughters = spawnVDecay(vertex, params, makeRng(params.seed, salt + ':vdecay' + i));
+      daughters.forEach(d => {
+        if (d.length > 10) tracks.push({ pts: d, kind: 'vdecay', weight: intensity * 0.95 });
+      });
+    }
+  }
+
+  return tracks;
+}
+
+export function generateScene(params) {
+  const rng = makeRng(params.seed, 'scene');
+  const tracks = [];
+
+  // Foreground event, slightly off-centre
+  const fgVertex = { x: (rng() - 0.5) * 0.3, y: (rng() - 0.5) * 0.3 };
+  tracks.push(...generateOneEvent(params, fgVertex, 1.0, 'fg'));
+
+  // Background "history" events
+  const nBg = params.bgEvents || 0;
+  for (let i = 0; i < nBg; i++) {
+    const bgRng = makeRng(params.seed, 'bg' + i);
+    const vx = (bgRng() - 0.5) * 1.7, vy = (bgRng() - 0.5) * 1.7;
+    const intensity = params.bgIntensity * (0.5 + bgRng() * 0.5);
+    tracks.push(...generateOneEvent(
+      { ...params, primaries: Math.round(params.primaries * 0.6), vdecay: 0 },
+      { x: vx, y: vy }, intensity, 'bg' + i
+    ));
+  }
+
+  // Cosmic/transient straight tracks crossing the frame
+  const nCosmic = Math.round(params.cosmics || 0);
+  for (let i = 0; i < nCosmic; i++) {
+    const cRng = makeRng(params.seed, 'cosmic' + i);
+    const pts = cosmicTrack(params, cRng);
+    if (pts.length > 8) tracks.push({ pts, kind: 'cosmic', weight: 0.7 + cRng() * 0.3 });
+  }
+
+  // Sweepers — big gentle arcs across the frame
+  const nSweep = Math.round(params.sweepers || 0);
+  for (let i = 0; i < nSweep; i++) {
+    const sRng = makeRng(params.seed, 'sweep' + i);
+    const pts = sweeperTrack(params, sRng);
+    if (pts.length > 8) tracks.push({ pts, kind: 'sweep', weight: 0.75 + sRng() * 0.25 });
+  }
+
+  const shock = generateShock(params, makeRng(params.seed, 'shock'));
+  const artifacts = generateArtifacts(params, makeRng(params.seed, 'artifacts'));
+  const instrument = generateInstrument(params, makeRng(params.seed, 'instrument'));
+
+  // deterministic archival metadata (so exports are reproducible from the seed)
+  const hash = cyrb53(params.seed);
+  const ds = parseInt(hash.slice(0, 8), 16);
+  const plate = (parseInt(hash.slice(-3), 16) % 999).toString().padStart(3, '0');
+  const year = 1971 + (ds % 11);
+  const month = 1 + ((ds >> 4) % 12);
+  const day = 1 + ((ds >> 8) % 28);
+  const exposure = `${year}.${String(month).padStart(2, '0')}.${String(day).padStart(2, '0')}`;
+  const lab = pick(makeRng(params.seed, 'lab'), LABS);
+
+  return { tracks, vertex: fgVertex, shock, artifacts, instrument, hash, plate, exposure, lab };
+}