GLB Wireframe / Solid Toggle Viewer — Free Three.js glTF Cross-Fade Snippet

<div class="gwf-wrap">
  <canvas id="gwfCanvas"></canvas>
  <div class="gwf-hint">Drag to orbit · Ctrl/Cmd + scroll to zoom</div>
  <div class="gwf-zoom">
    <span class="gwf-zoom-label">+</span>
    <input type="range" id="gwfZoom" class="gwf-zoom-slider" min="0" max="100" step="1" />
    <span class="gwf-zoom-label">&minus;</span>
  </div>
  <div class="gwf-panel">
    <div class="gwf-panel-title">Render mode</div>
    <input type="range" id="gwfMix" class="gwf-mix-slider" min="0" max="100" step="1" value="0" />
    <div class="gwf-panel-row"><span>Solid</span><span id="gwfMixLabel">Solid</span><span>Wireframe</span></div>
  </div>
</div>

*{box-sizing:border-box;margin:0;padding:0}
body{font-family:system-ui,-apple-system,sans-serif;min-height:100vh;display:flex;align-items:center;justify-content:center;background:#0a0b12;color:#fff;padding:24px}
.gwf-wrap{position:relative;width:min(720px,94vw);height:min(520px,80vh);border-radius:20px;overflow:hidden;background:radial-gradient(60% 60% at 50% 42%,#161a24,#08090d);border:1px solid rgba(255,255,255,.08)}
#gwfCanvas{display:block;width:100%;height:100%;cursor:grab}
#gwfCanvas:active{cursor:grabbing}
.gwf-hint{position:absolute;top:18px;left:18px;font-size:11.5px;font-weight:600;color:#b7c0da;background:rgba(10,12,20,.55);padding:7px 14px;border-radius:999px;backdrop-filter:blur(6px);border:1px solid rgba(255,255,255,.08)}
.gwf-zoom{position:absolute;right:18px;top:18px;bottom:96px;width:32px;display:flex;flex-direction:column;align-items:center;gap:8px;background:rgba(10,12,20,.55);border:1px solid rgba(255,255,255,.1);border-radius:999px;padding:10px 0;backdrop-filter:blur(6px)}
.gwf-zoom-label{font-size:12px;font-weight:700;color:#b7c0da;line-height:1;user-select:none}
.gwf-zoom-slider{flex:1;width:6px;-webkit-appearance:slider-vertical;writing-mode:vertical-lr;direction:rtl;accent-color:#22d3ee;cursor:pointer}
.gwf-panel{position:absolute;left:18px;right:18px;bottom:18px;background:rgba(10,12,20,.65);border:1px solid rgba(255,255,255,.1);border-radius:16px;padding:14px 16px;backdrop-filter:blur(10px)}
.gwf-panel-title{font-size:11px;font-weight:700;letter-spacing:.08em;text-transform:uppercase;color:#8b93ad;margin-bottom:8px}
.gwf-mix-slider{width:100%;accent-color:#22d3ee;cursor:pointer}
.gwf-panel-row{display:flex;justify-content:space-between;font-size:11.5px;color:#9aa0b8;margin-top:6px}
#gwfMixLabel{font-weight:700;color:#67e8f9}

const canvas = document.getElementById('gwfCanvas');
const renderer = new THREE.WebGLRenderer({ canvas, antialias: true, alpha: true });
renderer.setPixelRatio(Math.min(window.devicePixelRatio, 2));

const scene = new THREE.Scene();
const camera = new THREE.PerspectiveCamera(40, 1, 0.1, 50);
camera.position.set(1.7, 1.0, 3.1);

const controls = new THREE.OrbitControls(camera, renderer.domElement);
controls.enableDamping = true;
controls.dampingFactor = 0.08;
controls.target.set(0, 0.2, 0);
controls.minDistance = 1.5;
controls.maxDistance = 8;

// OrbitControls' own wheel-zoom is turned off on purpose: left on, it calls
// preventDefault() on every wheel event over the canvas, which would block
// normal page scrolling around this card. Zoom is reimplemented below as an
// explicit, opt-in gesture (a slider, and Ctrl/Cmd + scroll) instead.
controls.enableZoom = false;

const zoomSlider = document.getElementById('gwfZoom');

function setZoomDistance(distance) {
  const clamped = THREE.MathUtils.clamp(distance, controls.minDistance, controls.maxDistance);
  const offset = camera.position.clone().sub(controls.target);
  offset.setLength(clamped || 0.001);
  camera.position.copy(controls.target).add(offset);
  const t = (clamped - controls.minDistance) / (controls.maxDistance - controls.minDistance);
  zoomSlider.value = String(Math.round((1 - t) * 100));
}

setZoomDistance(camera.position.distanceTo(controls.target));

zoomSlider.addEventListener('input', () => {
  const t = 1 - Number(zoomSlider.value) / 100;
  setZoomDistance(controls.minDistance + t * (controls.maxDistance - controls.minDistance));
});

canvas.addEventListener('wheel', (e) => {
  if (!e.ctrlKey && !e.metaKey) return; // plain scroll always passes through to the page
  e.preventDefault();
  const current = camera.position.distanceTo(controls.target);
  setZoomDistance(current + e.deltaY * 0.01);
}, { passive: false });

scene.add(new THREE.AmbientLight(0x445066, 0.7));
const key = new THREE.DirectionalLight(0xffffff, 1.8);
key.position.set(4, 6, 5);
scene.add(key);
const fill = new THREE.DirectionalLight(0x93c5fd, 0.5);
fill.position.set(-5, 2, 3);
scene.add(fill);

const ground = new THREE.Mesh(
  new THREE.CircleGeometry(3, 44),
  new THREE.MeshStandardMaterial({ color: 0x14161f, roughness: 1 })
);
ground.rotation.x = -Math.PI / 2;
ground.position.y = -0.85;
scene.add(ground);

// Two independent copies of every mesh: a solid-shaded clone and a
// wireframe clone sharing the same underlying geometry, layered exactly
// on top of each other. Cross-fading their opacity — rather than flipping
// a single material's .wireframe boolean on and off — is what makes a
// smooth, continuous 0-100 blend possible instead of a hard binary snap.
const solidGroup = new THREE.Group();
const wireGroup = new THREE.Group();
scene.add(solidGroup, wireGroup);

function buildDualMaterialModel(sourceRoot) {
  sourceRoot.traverse((node) => {
    if (!node.isMesh) return;
    const solidMesh = new THREE.Mesh(node.geometry, new THREE.MeshStandardMaterial({ color: 0x67e8f9, roughness: 0.45, metalness: 0.2, transparent: true, opacity: 1 }));
    const wireMesh = new THREE.Mesh(node.geometry, new THREE.MeshBasicMaterial({ color: 0x22d3ee, wireframe: true, transparent: true, opacity: 0 }));
    solidMesh.matrix.copy(node.matrixWorld);
    wireMesh.matrix.copy(node.matrixWorld);
    solidMesh.matrixAutoUpdate = false;
    wireMesh.matrixAutoUpdate = false;
    solidGroup.add(solidMesh);
    wireGroup.add(wireMesh);
  });
}

// Khronos' official sample-asset "Antique Camera" — a real, freely-licensed
// .glb with clean, readable edges that make a wireframe overlay genuinely
// legible rather than an illegible tangle.
const MODEL_URL = 'https://cdn.jsdelivr.net/gh/KhronosGroup/glTF-Sample-Assets@main/Models/AntiqueCamera/glTF-Binary/AntiqueCamera.glb';

const loader = new THREE.GLTFLoader();
loader.load(
  MODEL_URL,
  (gltf) => {
    const model = gltf.scene;
    // Auto-fit rather than a hardcoded scale factor: different .glb exports
    // (and loader versions) can decode the same source asset at wildly
    // different raw sizes, so measuring the loaded geometry and scaling it
    // to a known target height is far more reliable than guessing a number.
    const box = new THREE.Box3().setFromObject(model);
    const size = box.getSize(new THREE.Vector3());
    const maxDim = Math.max(size.x, size.y, size.z) || 1;
    model.scale.setScalar(1.7 / maxDim);
    model.updateMatrixWorld(true);
    const fitted = new THREE.Box3().setFromObject(model);
    const liftY = -0.85 - fitted.min.y;
    model.position.y += liftY;
    model.updateMatrixWorld(true);
    buildDualMaterialModel(model);
  },
  undefined,
  (err) => {
    // Honest failure state: if the CDN model can't load, build a simple
    // placeholder that still supports the same solid/wireframe blend.
    console.error('GLB failed to load, showing a placeholder instead:', err);
    const placeholder = new THREE.Group();
    const mesh = new THREE.Mesh(new THREE.IcosahedronGeometry(0.9, 1));
    mesh.position.y = 0.1;
    placeholder.add(mesh);
    buildDualMaterialModel(placeholder);
  }
);

function applyMix(t01) {
  solidGroup.children.forEach((m) => { m.material.opacity = 1 - t01; });
  wireGroup.children.forEach((m) => { m.material.opacity = t01; });
}

const mixSlider = document.getElementById('gwfMix');
const mixLabel = document.getElementById('gwfMixLabel');
mixSlider.addEventListener('input', () => {
  const t = Number(mixSlider.value) / 100;
  applyMix(t);
  mixLabel.textContent = t < 0.02 ? 'Solid' : t > 0.98 ? 'Wireframe' : Math.round(t * 100) + '% wire';
});
applyMix(0);

function resize() {
  const w = canvas.clientWidth, h = canvas.clientHeight;
  renderer.setSize(w, h, false);
  camera.aspect = w / h;
  camera.updateProjectionMatrix();
}

function animate() {
  requestAnimationFrame(animate);
  controls.update();
  renderer.render(scene, camera);
}

resize();
window.addEventListener('resize', resize);
animate();