3D Tiles Point Cloud Classification

<!--
  示例：点云分类着色
  说明：三类点云分别使用灰、蓝、绿三种颜色，树冠按球状分布打点
  核心逻辑：分类色表 → 生成点时按类别取色 → 相机俯瞰
  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>点云分类着色</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">灰色地面、蓝色建筑立面、绿色树冠。树冠点按球面随机分布。</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 baseLon = 116.391, baseLat = 39.906;
  var DLON = 1.17e-5, DLAT = 8.98e-6;
  var pc = scene.primitives.add(new Cesium.PointPrimitiveCollection());
  var seed = 44;
  function rnd() { seed = (seed * 9301 + 49297) % 233280; return seed / 233280; }

  var CLASS = {
    ground: Cesium.Color.fromCssColorString('#8a939f').withAlpha(0.75),
    building: Cesium.Color.fromCssColorString('#4d7cff'),
    veg: Cesium.Color.fromCssColorString('#3ecf8e')
  };

  /* 地面 */
  for (var gx = -15; gx <= 15; gx += 1.4) {
    for (var gy = -10; gy <= 10; gy += 1.4) {
      pc.add({
        position: Cesium.Cartesian3.fromDegrees(baseLon + gx * DLON, baseLat + gy * DLAT, 0),
        pixelSize: 2, color: CLASS.ground
      });
    }
  }

  /* 建筑 */
  var blocks = [
    { dx: -9, dy: 2, w: 14, d: 12, h: 30 },
    { dx: 8, dy: 4, w: 12, d: 12, h: 42 },
    { dx: 0, dy: -6, w: 18, d: 10, h: 22 }
  ];
  blocks.forEach(function (b) {
    for (var hh = 1; hh < b.h; hh += 1.5) {
      [-1, 1].forEach(function (sx) {
        [-1, 1].forEach(function (sy) {
          pc.add({
            position: Cesium.Cartesian3.fromDegrees(
              baseLon + (b.dx + sx * b.w / 2) * DLON,
              baseLat + (b.dy + sy * b.d / 2) * DLAT, hh),
            pixelSize: 2.4, color: CLASS.building
          });
        });
      });
    }
  });

  /* 植被：树上打点 */
  for (var i = 0; i < 26; i++) {
    var cx = -14 + rnd() * 28, cy = -9 + rnd() * 18, ch = 3 + rnd() * 4;
    for (var k = 0; k < 22; k++) {
      var r = rnd() * ch * 0.8;
      var a = rnd() * Math.PI * 2;
      pc.add({
        position: Cesium.Cartesian3.fromDegrees(
          baseLon + (cx + Math.cos(a) * r) * DLON,
          baseLat + (cy + Math.sin(a) * r) * DLAT,
          ch * 0.8 + rnd() * ch * 0.7),
        pixelSize: 2.2, color: CLASS.veg
      });
    }
  }

  viewer.camera.flyTo({
    destination: Cesium.Cartesian3.fromDegrees(116.3868, 39.8990, 120),
    orientation: { heading: Cesium.Math.toRadians(20), pitch: Cesium.Math.toRadians(-18), roll: 0 },
    duration: 0
  });
})();
</script>
</body>
</html>