🎨 closer: colourise the grayscale moons — directorial hue tint (opus)

USGS has no colour equirect for Europa/Callisto/Titan/Phobos/Charon, so those
mosaics shipped grayscale. Multiply each by its characteristic hue at render
(bodies.js `tint`; moons.js tint-preserving loader keeps the real surface detail,
adds the iconic colour — Titan orange, Europa/Charon tan, Callisto/Phobos warm).
Io/Ganymede/Triton stay true USGS colour (white multiplier). Flagged in CREDITS as
a directorial (non-data) choice per Part ω.2. User-directed ("colourise the moons").

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

assets/textures/CREDITS.md

@@ -53,6 +53,13 @@ under budget). Downloaded 2026-07-16.
 Host base URL: `https://planetarymaps.usgs.gov/mosaic/` (served from the USGS
 `asc-pds-services` bucket). USGS terms: <https://www.usgs.gov/information-policies-and-instructions/copyrights-and-credits>.
 
+**Directorial colourisation (PERIHELION closer).** USGS has no colour equirect for
+Europa, Callisto, Titan, Phobos and Charon, so those mosaics ship grayscale. The
+app multiplies each by its characteristic hue at render (`bodies.js` `tint`:
+Titan orange, Europa/Charon tan, Callisto/Phobos warm-brown) — the *real surface
+detail is preserved*; only the colour is an explicit directorial choice, not data.
+Io, Ganymede and Triton are USGS colour mosaics and render untinted.
+
 **Truth boundary (brief §7b):** these are the *real data* textures — real worlds
 get real maps. The stylized grimoire portraits in `../art/grimoire/` are the
 *aesthetic* layer (generated art), kept visually and directorially separate.

js/bodies.js

@@ -62,18 +62,18 @@ export const BODIES = {
     parent: 'earth', moonOrbit: { aKm: 384400, periodDays: 27.322 } },
 
   phobos: { name: 'Phobos', type: 'moon', radiusKm: 11.27, color: '#8a7c6e',
-    texture: '1k_phobos.jpg', parent: 'mars', moonOrbit: { aKm: 9378, periodDays: 0.319 } },
+    texture: '1k_phobos.jpg', tint: '#a08a76', parent: 'mars', moonOrbit: { aKm: 9378, periodDays: 0.319 } },
   deimos: { name: 'Deimos', type: 'moon', radiusKm: 6.2, color: '#9a8c7a',
     texture: null, parent: 'mars', moonOrbit: { aKm: 23459, periodDays: 1.262 } },
 
   io:       { name: 'Io', type: 'moon', radiusKm: 1821.6, color: '#e8d24b',
     texture: '1k_io.jpg', parent: 'jupiter', moonOrbit: { aKm: 421700, periodDays: 1.769 } },
   europa:   { name: 'Europa', type: 'moon', radiusKm: 1560.8, color: '#c9b79c',
-    texture: '1k_europa.jpg', parent: 'jupiter', moonOrbit: { aKm: 671034, periodDays: 3.551 } },
+    texture: '1k_europa.jpg', tint: '#e6dcc8', parent: 'jupiter', moonOrbit: { aKm: 671034, periodDays: 3.551 } },
   ganymede: { name: 'Ganymede', type: 'moon', radiusKm: 2634.1, color: '#9b8e7e',
     texture: '1k_ganymede.jpg', parent: 'jupiter', moonOrbit: { aKm: 1070412, periodDays: 7.155 } },
   callisto: { name: 'Callisto', type: 'moon', radiusKm: 2410.3, color: '#6b5f52',
-    texture: '1k_callisto.jpg', parent: 'jupiter', moonOrbit: { aKm: 1882709, periodDays: 16.689 } },
+    texture: '1k_callisto.jpg', tint: '#9a8778', parent: 'jupiter', moonOrbit: { aKm: 1882709, periodDays: 16.689 } },
 
   mimas:     { name: 'Mimas', type: 'moon', radiusKm: 198.2, color: '#c8c8c8',
     texture: null, parent: 'saturn', moonOrbit: { aKm: 185539, periodDays: 0.942 } },
@@ -86,7 +86,7 @@ export const BODIES = {
   rhea:      { name: 'Rhea', type: 'moon', radiusKm: 763.8, color: '#c4c4c4',
     texture: null, parent: 'saturn', moonOrbit: { aKm: 527068, periodDays: 4.518 } },
   titan:     { name: 'Titan', type: 'moon', radiusKm: 2574.7, color: '#d9a441',
-    texture: '1k_titan.jpg', parent: 'saturn', moonOrbit: { aKm: 1221870, periodDays: 15.945 } },
+    texture: '1k_titan.jpg', tint: '#e0a63f', parent: 'saturn', moonOrbit: { aKm: 1221870, periodDays: 15.945 } },
   iapetus:   { name: 'Iapetus', type: 'moon', radiusKm: 734.5, color: '#8a7a5e',
     texture: null, parent: 'saturn', moonOrbit: { aKm: 3560851, periodDays: 79.33 } },
 
@@ -114,7 +114,7 @@ export const BODIES = {
                 w: 113.76329, ma: 14.86012204, epoch: 2451545.0 },
   },
   charon: { name: 'Charon', type: 'moon', radiusKm: 606.0, color: '#b3a894',
-    texture: '1k_charon.jpg', parent: 'pluto', moonOrbit: { aKm: 19591, periodDays: 6.387 } },
+    texture: '1k_charon.jpg', tint: '#c4b7a4', parent: 'pluto', moonOrbit: { aKm: 19591, periodDays: 6.387 } },
 };
 
 // Ordered planet ids (draw / menu order).

js/layers/moons.js

@@ -17,7 +17,17 @@ export default function create(ctx) {
     const mesh = new THREE.Mesh(new THREE.SphereGeometry(1, 24, 16), mat);
     mesh.visible = true;
     scene.add(mesh);
-    loadTextureInto(mat, b.texture); // NASA/USGS map when present; flat color otherwise (§7 fallback)
+    if (b.tint) {
+      // Directorial colourisation: the USGS mosaics for these moons are grayscale
+      // (no color equirect exists), so multiply the real surface by the moon's
+      // characteristic hue — keeps true detail, adds the iconic colour. On a load
+      // error the flat b.color already set on the material stands (§7 fallback).
+      new THREE.TextureLoader().load(CONFIG.textures.path + b.texture, (tex) => {
+        tex.colorSpace = THREE.SRGBColorSpace; mat.map = tex; mat.color.set(b.tint); mat.needsUpdate = true;
+      });
+    } else {
+      loadTextureInto(mat, b.texture); // NASA/USGS map when present; flat color otherwise (§7 fallback)
+    }
     registerPick(mesh, id);
     const lbl = makeLabel(mesh, b.name, 'body-label moon');
     lbl.obj.visible = false; // CSS2DRenderer honors obj.visible (not div.style.display)