Classification

<!--
  示例：影像分类到瓦片表面
  说明：地面色块分别按地形、3D Tiles 与两者同时投递，压盖结果不同
  核心逻辑：classificationType = TERRAIN / CESIUM_3D_TILE / BOTH → 地面图元分类
  依赖：CesiumJS 1.121 · jsDelivr CDN
-->
<!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>影像分类到瓦片表面</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%}
  .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}

  .cesium-viewer-bottom .cesium-widget-credits,.cesium-viewer-animationContainer,
  .cesium-viewer-timelineContainer{display:none!important}
</style>
</head>
<body>
<div id="c"></div>
<div class="tip">三块色带分别投到地形、瓦片和两者，落到模型上的那块明显贴在表面。</div>
<script src="https://cdn.jsdelivr.net/npm/cesium@1.121.0/Build/Cesium/Cesium.js"></script>
<script>
(function () {
  'use strict';

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  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;

  function glbBytes(json, bin) {
    var jb = new TextEncoder().encode(JSON.stringify(json));
    var jpad = (4 - jb.length % 4) % 4, bpad = (4 - bin.length % 4) % 4;
    var jl = jb.length + jpad, bl = bin.length + bpad;
    var out = new Uint8Array(12 + 8 + jl + 8 + bl), dv = new DataView(out.buffer);
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    return out;
  }

  /* 一块很扁的大板，充当可分类的瓦片表面 */
  function slabGlb() {
    var w = 400, h = 2, d = 400;
    var hx = w / 2, hz = d / 2;
    var faces = [
      [[hx, 0, hz], [hx, 0, -hz], [hx, h, -hz], [hx, h, hz], [1, 0, 0]],
      [[-hx, 0, -hz], [-hx, 0, hz], [-hx, h, hz], [-hx, h, -hz], [-1, 0, 0]],
      [[-hx, h, hz], [hx, h, hz], [hx, h, -hz], [-hx, h, -hz], [0, 1, 0]],
      [[-hx, 0, -hz], [hx, 0, -hz], [hx, 0, hz], [-hx, 0, hz], [0, -1, 0]],
      [[-hx, 0, hz], [hx, 0, hz], [hx, h, hz], [-hx, h, hz], [0, 0, 1]],
      [[hx, 0, -hz], [-hx, 0, -hz], [-hx, h, -hz], [hx, h, -hz], [0, 0, -1]]
    ];
    var pos = [], nor = [], idx = [], base = 0;
    faces.forEach(function (f) {
      for (var i = 0; i < 4; i++) { pos.push(f[i][0], f[i][1], f[i][2]); nor.push(f[4][0], f[4][1], f[4][2]); }
      idx.push(base, base + 1, base + 2, base, base + 2, base + 3);
      base += 4;
    });
    var p = new Float32Array(pos), n = new Float32Array(nor), ix = new Uint16Array(idx);
    var pb = p.byteLength, nb = n.byteLength, ib = ix.byteLength;
    var bin = new Uint8Array(pb + nb + ib);
    bin.set(new Uint8Array(p.buffer), 0);
    bin.set(new Uint8Array(n.buffer), pb);
    bin.set(new Uint8Array(ix.buffer), pb + nb);
    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: [0.24, 0.3, 0.37, 1], metallicFactor: 0, roughnessFactor: 0.95
      }, doubleSided: true }],
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      ],
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    };
    return new Blob([glbBytes(json, bin)], { type: 'model/gltf-binary' });
  }

  var origin = Cesium.Cartesian3.fromDegrees(116.3895, 39.9035, 0);
  var enu = Cesium.Transforms.eastNorthUpToFixedFrame(origin);
  var json = {
    asset: { version: '1.1' },
    geometricError: 400,
    root: {
      transform: Cesium.Matrix4.toArray(enu),
      boundingVolume: { box: [0, 0, 0, 220, 0, 0, 0, 8, 0, 0, 0, 220] },
      geometricError: 0,
      content: { uri: URL.createObjectURL(slabGlb()) }
    }
  };
  var tsUrl = URL.createObjectURL(new Blob([JSON.stringify(json)], { type: 'application/json' }));

  Cesium.Cesium3DTileset.fromUrl(tsUrl).then(function (tileset) {
    scene.primitives.add(tileset);
    viewer.zoomTo(tileset, new Cesium.HeadingPitchRange(0, Cesium.Math.toRadians(-55), 420));
  });

  function band(dx, color, type) {
    viewer.entities.add({
      polygon: {
        hierarchy: Cesium.Cartesian3.fromDegreesArray([
          116.3865 + dx, 39.9020, 116.3888 + dx, 39.9020,
          116.3888 + dx, 39.9048, 116.3865 + dx, 39.9048
        ]),
        material: Cesium.Color.fromCssColorString(color).withAlpha(0.75),
        classificationType: type
      }
    });
  }

  band(0.0000, '#4d86c8', Cesium.ClassificationType.TERRAIN);
  band(0.0030, '#5bb08a', Cesium.ClassificationType.CESIUM_3D_TILE);
  band(0.0060, '#d08a4e', Cesium.ClassificationType.BOTH);
  viewer.camera.flyTo({
    destination: Cesium.Cartesian3.fromDegrees(116.3895, 39.9008, 420),
    orientation: { heading: 0, pitch: Cesium.Math.toRadians(-45), roll: 0 },
    duration: 0
  });
})();
</script>
</body>
</html>