3D Models Dev

<!--
  示例：模型的缩放、朝向与最小像素尺寸
  说明：同一份 GLB 生成三份实例，分别调 scale、orientation 与 minimumPixelSize，观察各自差异
  核心逻辑：Entity + ModelGraphics → scale / minimumPixelSize / orientation / silhouette
  依赖：CesiumJS 1.121 · jsDelivr CDN
-->
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<head>
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<meta name="viewport" content="width=device-width, initial-scale=1">
<title>模型缩放与朝向</title>
<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/cesium@1.121.0/Build/Cesium/Widgets/widgets.css">
<style>
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       font:13px/1.6 -apple-system,"Segoe UI","PingFang SC",sans-serif}
  #c{height:100%}
  .tip{position:absolute;left:12px;top:12px;z-index:5;
       background:rgba(23,28,35,.9);border:1px solid #2a313b;border-radius:6px;
       padding:8px 12px;font-size:12px;color:#a2a9b6;max-width:320px;line-height:1.6}
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<body>
<div id="c"></div>
<div class="tip">左：原始尺寸。中：scale 放大 2.5 倍并转 45°。右：缩到 1 px 级别时靠 minimumPixelSize 保底，远处仍可见。</div>
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(function () {
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  scene.sun.show = false;
  scene.moon.show = false;
  if (scene.skyAtmosphere) scene.skyAtmosphere.show = false;

  function glbBytes(json, bin) {
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  function boxGlb(w, h, d, color) {
    var hx = w / 2, hz = d / 2;
    var faces = [
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      [[-hx, 0, -hz], [-hx, 0, hz], [-hx, h, hz], [-hx, h, -hz], [-1, 0, 0]],
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      [[-hx, 0, hz], [hx, 0, hz], [hx, h, hz], [-hx, h, hz], [0, 0, 1]],
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    var json = {
      asset: { version: '2.0' },
      scene: 0,
      scenes: [{ nodes: [0] }],
      nodes: [{ mesh: 0 }],
      meshes: [{ primitives: [{ attributes: { POSITION: 0, NORMAL: 1 }, indices: 2, material: 0 }] }],
      materials: [{
        pbrMetallicRoughness: {
          baseColorFactor: [color[0], color[1], color[2], 1],
          metallicFactor: 0, roughnessFactor: 0.85
        },
        doubleSided: true
      }],
      accessors: [
        { bufferView: 0, componentType: 5126, count: 24, type: 'VEC3',
          min: [-hx, 0, -hz], max: [hx, h, hz] },
        { bufferView: 1, componentType: 5126, count: 24, type: 'VEC3' },
        { bufferView: 2, componentType: 5123, count: 36, type: 'SCALAR' }
      ],
      bufferViews: [
        { buffer: 0, byteOffset: 0, byteLength: pb, target: 34962 },
        { buffer: 0, byteOffset: pb, byteLength: nb, target: 34962 },
        { buffer: 0, byteOffset: pb + nb, byteLength: ib, target: 34963 }
      ],
      buffers: [{ byteLength: pb + nb + ib }]
    };
    return new Blob([glbBytes(json, bin)], { type: 'model/gltf-binary' });
  }

  var url = URL.createObjectURL(boxGlb(10, 24, 10, [0.55, 0.63, 0.74]));
  var hpr = new Cesium.HeadingPitchRoll();

  /* 三份实例排成一排，观察参数差异 */
  var layout = [
    { lon: 116.3894, scale: 1,   heading: 0,                minPx: 0 },
    { lon: 116.3910, scale: 2.5, heading: Cesium.Math.toRadians(45), minPx: 0 },
    { lon: 116.3926, scale: 1,   heading: Cesium.Math.toRadians(120), minPx: 6 }
  ];

  layout.forEach(function (item, i) {
    var pos = Cesium.Cartesian3.fromDegrees(item.lon, 39.907, 0);
    hpr.heading = item.heading;
    viewer.entities.add({
      position: pos,
      orientation: Cesium.Transforms.headingPitchRollQuaternion(pos, hpr),
      model: {
        uri: url,
        scale: item.scale,
        minimumPixelSize: item.minPx,
        maximumScale: 20000,
        silhouetteColor: Cesium.Color.fromCssColorString('#4d9bff'),
        silhouetteSize: i === 1 ? 2 : 0
      },
      label: {
        text: ['原尺寸', 'scale 2.5 · 转 45°', 'minimumPixelSize 6'][i],
        font: '500 12px sans-serif',
        fillColor: Cesium.Color.WHITE,
        pixelOffset: new Cesium.Cartesian2(0, -14),
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      }
    });
  });

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    destination: Cesium.Cartesian3.fromDegrees(116.391, 39.9005, 130),
    orientation: { heading: 0, pitch: Cesium.Math.toRadians(-22), roll: 0 },
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