Function createModelSystem

src/model.js:29–291

({ scene, sharedUniforms, mossUniforms, defaultUrl })

 * @param {string} [o.defaultUrl]     GLB to load on start
 */
export function createModelSystem({ scene, sharedUniforms, mossUniforms, defaultUrl }) {
  const loader = new GLTFLoader();

  // Transform wrapper — user controls live here; the GLB is recentered inside.
  const group = new THREE.Group();
  group.visible = false; // hidden until the user toggles it on
  scene.add(group);
  let current = null; // the loaded GLB scene
  const processed = new Set(); // materials we've already made mossy

  /* ---- moss-accumulation uniforms (shared bits + own knobs) -------------- */
  const moss = {
    uMossEnabled: mossUniforms.uMossEnabled, // shared master on/off gate
    uModelInv: { value: new THREE.Matrix4() }, // world -> model space (locks the pattern)
    uMossSeed: { value: new THREE.Vector2(3.0, 7.0) }, // pan the coverage noise
    uMossScale: { value: 0.9 }, // coverage noise frequency
    uMossCoverage: { value: 0.7 }, // 0 = bare model, 1 = fully capped
    uMossEdge: { value: 0.15 }, // coverage shoreline softness
    uMossThickness: { value: 0.05 }, // displaced layer depth (world units)
    uMossFlatThreshold: { value: 0.35 }, // how upward a face must be to collect
    // --- texture & look (maps + tint shared from the ground moss) ----------
    uMossMap: mossUniforms.uMossMap,
    uMossRoughnessMap: mossUniforms.uMossRoughnessMap,
    uMossNormalMap: mossUniforms.uMossNormalMap,
    uMossAoMap: mossUniforms.uMossAoMap,
    uMossColor: mossUniforms.uMossColor,
    uMossTexScale: { value: 2.0 }, // model-space moss tiling (finer than the ground)
    uMossRoughness: { value: 1.0 }, // scales the sampled moss roughness
    uMossAoStrength: { value: 1.0 }, // moss ambient-occlusion strength
    uMossBump: { value: 0.5 }, // micro surface relief strength
    uMossBumpScale: { value: 3.0 }, // micro relief frequency
  };

  // Shared GLSL (uniforms + noise + the coverage/relief helpers), injected into
  // BOTH stages: the vertex stage grows the layer, the fragment stage shades it.
  const MOSS_GLSL = /* glsl */ `
  varying vec3 vWorldNormalW;
  varying vec3 vModelPosW;
  uniform float uMossEnabled;
  uniform mat4  uModelInv;
  uniform vec2  uMossSeed;
  uniform float uMossScale;
  uniform float uMossCoverage;
  uniform float uMossEdge;
  uniform float uMossThickness;
  uniform float uMossFlatThreshold;
  uniform sampler2D uMossMap;
  uniform sampler2D uMossRoughnessMap;
  uniform sampler2D uMossNormalMap;
  uniform sampler2D uMossAoMap;
  uniform vec3  uMossColor;
  uniform float uMossTexScale;
  uniform float uMossRoughness;
  uniform float uMossAoStrength;
  uniform float uMossBump;
  uniform float uMossBumpScale;

  vec3 permute(vec3 x) { return mod(((x * 34.0) + 1.0) * x, 289.0); }