solargod/js/layers/planets.js

// SOLARGOD planets layer (Stage 1) — the eight planets + Pluto as textured,
// exaggerated spheres on compressed orbit paths, with labels. Positions come from
// ctx.bodyWorld (computed centrally in main.js); this layer only renders. Orbit
// geometry is rebuilt only when the MEGA/TRUE exponent is animating or elements
// drift past CONFIG.orbitRebuildCy (brief §11).

export default function create(ctx) {
  const { THREE, scene, CONFIG, lib, ui, scale, ephem, bodies, worldGroup,
          clock, focus, toLocal, effectiveE, makeLabel, registerPick, loadTextureInto, PLANET_ORDER } = ctx;

  const ROSTER = [...PLANET_ORDER, 'pluto'];
  const orbitMat = new THREE.LineBasicMaterial({ color: CONFIG.colors.orbit, transparent: true, opacity: 0.6 });
  const N = CONFIG.orbitSamples;
  const entries = [];
  const tmp = new THREE.Vector3();
  const _v = {};

  for (const id of ROSTER) {
    const b = bodies[id];
    // tilt group holds the spinning sphere so axial tilt + rotation compose.
    const group = new THREE.Group();
    const mat = new THREE.MeshStandardMaterial({ color: new THREE.Color(b.color), roughness: 1, metalness: 0 });
    const mesh = new THREE.Mesh(new THREE.SphereGeometry(1, 48, 32), mat);
    group.rotation.z = (b.axialTiltDeg || 0) * lib.DEG;
    group.add(mesh);
    scene.add(group);
    loadTextureInto(mat, b.texture);
    registerPick(mesh, id);
    const lbl = makeLabel(group, b.name, 'body-label');

    // orbit path (absolute view-world, lives under worldGroup)
    const geo = new THREE.BufferGeometry();
    geo.setAttribute('position', new THREE.BufferAttribute(new Float32Array((N + 1) * 3), 3));
    const line = new THREE.LineLoop(geo, orbitMat);
    line.frustumCulled = false;
    worldGroup.add(line);

    const e = { id, b, group, mesh, mat, geo, line, lbl, auPath: null, lastT: NaN };
    buildAuPath(e);
    fillView(e);
    entries.push(e);
  }

  function buildAuPath(e) {
    e.auPath = e.b.ephemId
      ? ephem.orbitPath(e.b.ephemId, clock.jd, N)
      : ephem.orbitPathFromElements(e.b.elements, N);
    e.lastT = lib.centuriesSinceJ2000(clock.jd);
  }
  function fillView(e) {
    const pos = e.geo.attributes.position.array;
    const au = e.auPath;
    for (let k = 0; k <= N; k++) {
      _v.x = au[k * 3]; _v.y = au[k * 3 + 1]; _v.z = au[k * 3 + 2];
      scale.viewFromEcl(_v, _v);
      pos[k * 3] = _v.x; pos[k * 3 + 1] = _v.y; pos[k * 3 + 2] = _v.z;
    }
    e.geo.attributes.position.needsUpdate = true;
    e.geo.computeBoundingSphere();
  }

  let showOrbits = true, showLabels = true;
  ui.addLayer('orbits', 'Orbit paths', true, (on) => { showOrbits = on; for (const e of entries) e.line.visible = on; });
  ui.addLayer('labels', 'Body labels', true, (on) => { showLabels = on; for (const e of entries) e.lbl.obj.visible = on; });
  ui.setStatus('orbits', `${entries.length} orbits`, 'ok');
  ui.setStatus('labels', 'names shown', 'ok');

  return {
    id: 'planets',
    onClockTick(simMs, jd, isLive) {
      const transitioning = scale.isTransitioning();
      for (const e of entries) {
        const abs = ctx.bodyWorld[e.id];
        if (!abs) continue;
        // position (floating-origin JS subtraction) + exaggerated radius
        toLocal(abs, e.group.position);
        const r = scale.drawRadius(e.b.radiusKm, effectiveE(e.id));
        e.mesh.scale.setScalar(r);
        // spin: fraction of a rotation since J2000 (retrograde via sign)
        if (e.b.rotationHours) {
          const rot = ((jd - lib.J2000_JD) * 24) / e.b.rotationHours;
          e.mesh.rotation.y = rot * 2 * Math.PI;
        }
        // focus highlight
        e.lbl.div.classList.toggle('focused', e.id === focus.id);
        // orbit rebuild only when needed
        const needAu = Math.abs(lib.centuriesSinceJ2000(jd) - e.lastT) > CONFIG.orbitRebuildCy;
        if (needAu) buildAuPath(e);
        if (needAu || transitioning) fillView(e);
      }
    },
  };
}