Model Animation

<!--
  示例：让内联 GLB 里的节点自己转起来
  要点：GLB 内写入 rotation 动画通道，模型加载后用 activeAnimations.addAll 循环播放
  依赖：CesiumJS 1.121 · jsDelivr CDN，模型与动画关键帧都在内存中生成
-->
<!DOCTYPE html>
<html lang="zh-CN">
<head>
<meta name="robots" content="noindex,follow">
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>GLB 节点动画</title>
<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/cesium@1.121.0/Build/Cesium/Widgets/widgets.css">
<style>
  html,body{height:100%;margin:0}
  body{background:#0e1116;color:#e6e8ec;overflow:hidden;
       font:13px/1.6 -apple-system,"Segoe UI","PingFang SC",sans-serif}
  #c{height:100%}
  .hud{position:absolute;left:12px;top:12px;z-index:5;background:rgba(23,28,35,.9);
       border:1px solid #2a313b;border-radius:6px;padding:9px 12px;font-size:12px;
       color:#a2a9b6;max-width:250px}
  .hud b{color:#e6e8ec;font-weight:600}
  .hud .row{margin-top:6px}
  input[type=range]{width:100%}
  .cesium-viewer-bottom .cesium-widget-credits,.cesium-viewer-animationContainer,
  .cesium-viewer-timelineContainer{display:none!important}
</style>
</head>
<body>
<div id="c"></div>
<div class="hud">
  <div><b>转子动画</b></div>
  <div class="row">转速 <span id="spVal">1.0</span> 倍</div>
  <div class="row"><input id="sp" type="range" min="0" max="4" step="0.25" value="1"></div>
  <div class="row" id="info">正在解析 GLB…</div>
</div>
<script src="https://cdn.jsdelivr.net/npm/cesium@1.121.0/Build/Cesium/Cesium.js"></script>
<script>
(function () {
  'use strict';

  var viewer = new Cesium.Viewer('c', {
    baseLayer: false,
    baseLayerPicker: false, geocoder: false, homeButton: false,
    sceneModePicker: false, navigationHelpButton: false,
    animation: false, timeline: false, fullscreenButton: false,
    infoBox: false, selectionIndicator: false
  });

  var scene = viewer.scene;
  scene.globe.baseColor = Cesium.Color.fromCssColorString('#1c2733');
  scene.backgroundColor = Cesium.Color.fromCssColorString('#0e1116');
  scene.skyBox.show = false;
  scene.sun.show = false;
  scene.moon.show = false;
  if (scene.skyAtmosphere) scene.skyAtmosphere.show = false;

  var CENTER = Cesium.Cartesian3.fromDegrees(116.389, 39.906, 58);

  /* ---------- 单位立方体：位置、法线、索引 ---------- */
  function cube() {
    var faces = [
      { n: [0, 0, 1],  v: [[-1, -1, 1], [1, -1, 1], [1, 1, 1], [-1, 1, 1]] },
      { n: [0, 0, -1], v: [[1, -1, -1], [-1, -1, -1], [-1, 1, -1], [1, 1, -1]] },
      { n: [1, 0, 0],  v: [[1, -1, 1], [1, -1, -1], [1, 1, -1], [1, 1, 1]] },
      { n: [-1, 0, 0], v: [[-1, -1, -1], [-1, -1, 1], [-1, 1, 1], [-1, 1, -1]] },
      { n: [0, 1, 0],  v: [[-1, 1, 1], [1, 1, 1], [1, 1, -1], [-1, 1, -1]] },
      { n: [0, -1, 0], v: [[-1, -1, -1], [1, -1, -1], [1, -1, 1], [-1, -1, 1]] }
    ];
    var pos = [], nrm = [], idx = [];
    faces.forEach(function (f, fi) {
      f.v.forEach(function (p) {
        pos.push(p[0] * 0.5, p[1] * 0.5, p[2] * 0.5);
        nrm.push(f.n[0], f.n[1], f.n[2]);
      });
      var b = fi * 4;
      idx.push(b, b + 1, b + 2, b, b + 2, b + 3);
    });
    return {
      pos: new Float32Array(pos),
      nrm: new Float32Array(nrm),
      idx: new Uint16Array(idx)
    };
  }

  /* ---------- 组装 GLB：chunks 顺序即 bufferView 顺序 ---------- */
  function buildGlb(gltf, chunks) {
    var len = 0;
    chunks.forEach(function (c) { len += c.data.byteLength; });
    var bin = new Uint8Array(len);
    var offset = 0;
    gltf.bufferViews = chunks.map(function (c) {
      var view = { buffer: 0, byteOffset: offset, byteLength: c.data.byteLength };
      if (c.target) view.target = c.target;
      bin.set(new Uint8Array(c.data.buffer, c.data.byteOffset, c.data.byteLength), offset);
      offset += c.data.byteLength;
      return view;
    });
    gltf.buffers = [{ byteLength: len }];

    var json = new TextEncoder().encode(JSON.stringify(gltf));
    var jsonPad = (4 - json.length % 4) % 4;
    var binPad = (4 - len % 4) % 4;
    var total = 12 + 8 + json.length + jsonPad + 8 + len + binPad;
    var out = new Uint8Array(total);
    var dv = new DataView(out.buffer);
    dv.setUint32(0, 0x46546C67, true);
    dv.setUint32(4, 2, true);
    dv.setUint32(8, total, true);
    dv.setUint32(12, json.length + jsonPad, true);
    dv.setUint32(16, 0x4E4F534A, true);
    out.set(json, 20);
    for (var i = 0; i < jsonPad; i++) out[20 + json.length + i] = 0x20;
    var p = 20 + json.length + jsonPad;
    dv.setUint32(p, len + binPad, true);
    dv.setUint32(p + 4, 0x004E4942, true);
    out.set(bin, p + 8);
    return out;
  }

  var geo = cube();

  /* 每 90° 一个关键帧，共 2.5 秒一圈 */
  var times = new Float32Array([0, 0.625, 1.25, 1.875, 2.5]);
  var quats = new Float32Array(20);
  for (var k = 0; k < 5; k++) {
    var half = (k * Math.PI / 2) / 2;
    quats[k * 4] = 0;
    quats[k * 4 + 1] = Math.sin(half);
    quats[k * 4 + 2] = 0;
    quats[k * 4 + 3] = Math.cos(half);
  }

  var gltf = {
    asset: { version: '2.0' },
    scene: 0,
    scenes: [{ nodes: [0, 1] }],
    /* 节点 0 是轮毂，节点 1 是横贯的长桨，绕 Y 轴旋转 */
    nodes: [
      { mesh: 0, scale: [0.34, 0.26, 0.34] },
      { mesh: 0, scale: [1.5, 0.09, 0.12] }
    ],
    meshes: [{ primitives: [{ attributes: { POSITION: 0, NORMAL: 1 }, indices: 2, material: 0 }] }],
    materials: [{
      pbrMetallicRoughness: {
        baseColorFactor: [0.42, 0.74, 0.95, 1.0],
        metallicFactor: 0.2,
        roughnessFactor: 0.4
      }
    }],
    animations: [{
      samplers: [{ input: 3, output: 4, interpolation: 'LINEAR' }],
      channels: [{ sampler: 0, target: { node: 1, path: 'rotation' } }]
    }],
    accessors: [
      { bufferView: 0, componentType: 5126, count: 24, type: 'VEC3',
        min: [-0.5, -0.5, -0.5], max: [0.5, 0.5, 0.5] },
      { bufferView: 1, componentType: 5126, count: 24, type: 'VEC3' },
      { bufferView: 2, componentType: 5123, count: 36, type: 'SCALAR' },
      { bufferView: 3, componentType: 5126, count: 5, type: 'SCALAR', min: [0], max: [2.5] },
      { bufferView: 4, componentType: 5126, count: 5, type: 'VEC4' }
    ]
  };

  var glb = buildGlb(gltf, [
    { data: geo.pos, target: 34962 },
    { data: geo.nrm, target: 34962 },
    { data: geo.idx, target: 34963 },
    { data: times },
    { data: quats }
  ]);

  var url = URL.createObjectURL(new Blob([glb], { type: 'model/gltf-binary' }));

  var model = null;
  var rotor = null;
  Cesium.Model.fromGltfAsync({ url: url, scale: 70 }).then(function (m) {
    m.modelMatrix = Cesium.Transforms.eastNorthUpToFixedFrame(CENTER);
    scene.primitives.add(m);
    model = m;
    rotor = m.activeAnimations.addAll({
      loop: Cesium.ModelAnimationLoop.REPEAT,
      speed: 1.0
    })[0];
    document.getElementById('info').textContent = '1 条 rotation 通道 · 5 个关键帧';
  }).catch(function (err) {
    document.getElementById('info').textContent = '解析失败：' + err.message;
  });

  /* 地面标签与支柱，交代模型落点 */
  viewer.entities.add({
    position: Cesium.Cartesian3.fromDegrees(116.389, 39.906, 0),
    cylinder: {
      length: 58, topRadius: 3, bottomRadius: 5,
      material: Cesium.Color.fromCssColorString('#5b6573')
    },
    label: {
      text: 'GLB 节点动画',
      font: '500 12px "Microsoft YaHei", sans-serif',
      fillColor: Cesium.Color.WHITE,
      pixelOffset: new Cesium.Cartesian2(0, 8),
      disableDepthTestDistance: Number.POSITIVE_INFINITY
    }
  });

  document.getElementById('sp').addEventListener('input', function () {
    var v = parseFloat(this.value);
    document.getElementById('spVal').textContent = v.toFixed(2);
    if (rotor) rotor.speed = v;
  });

  viewer.camera.flyTo({
    destination: Cesium.Cartesian3.fromDegrees(116.383, 39.899, 380),
    orientation: {
      heading: Cesium.Math.toRadians(20),
      pitch: Cesium.Math.toRadians(-16),
      roll: 0
    },
    duration: 0
  });
})();
</script>
</body>
</html>