3D Tiles Point Cloud Styling

<!--
  示例：点云的三套配色方案
  说明：五千个点按高度渐变、分档、单色三种方案轮换，右上角显示样式名
  核心逻辑：样式函数数组 → 每 2.5 秒遍历点改 color → HUD 显示当前方案
  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>点云的三套配色方案</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}
  .hud{position:absolute;right:12px;top:12px;z-index:5;background:rgba(23,28,35,.9);
       border:1px solid #2a313b;border-radius:6px;padding:6px 10px;font-size:12px;color:#a2a9b6}
</style>
</head>
<body>
<div id="c"></div>
<div class="tip">配色每 2.5 秒换一次：高度渐变 → 高度三档 → 单色。右上角显示当前方案。</div>
<div id="hud" class="hud">高度渐变</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 pts = [];
  var seed = 24;
  function rnd() { seed = (seed * 9301 + 49297) % 233280; return seed / 233280; }

  for (var i = 0; i < 5000; i++) {
    var x = -15 + rnd() * 30, y = -10 + rnd() * 20;
    var z = Math.pow(rnd(), 1.3) * 40;
    var p = pc.add({
      position: Cesium.Cartesian3.fromDegrees(baseLon + x * DLON, baseLat + y * DLAT, z),
      pixelSize: 3,
      color: Cesium.Color.WHITE
    });
    pts.push({ p: p, z: z });
  }

  /* 三套样式，每 2.5 秒切换一次 */
  var styles = [
    function (o) {                                   /* 高度渐变 */
      return Cesium.Color.fromHsl(0.62 - (o.z / 40) * 0.5, 0.75, 0.45 + (o.z / 40) * 0.2, 0.9);
    },
    function (o) {                                   /* 高度分档 */
      return Cesium.Color.fromCssColorString(o.z > 26 ? '#ff5c5c' : (o.z > 12 ? '#ffb44d' : '#4d7cff'));
    },
    function () {                                    /* 单色 */
      return Cesium.Color.fromCssColorString('#9aa6b8').withAlpha(0.85);
    }
  ];

  var si = 0;
  function apply() {
    var fn = styles[si % styles.length];
    pts.forEach(function (o) { o.p.color = fn(o); });
    document.getElementById('hud').textContent =
      ['高度渐变', '高度分档', '单色'][si % styles.length];
    si++;
    setTimeout(apply, 2500);
  }
  apply();

  viewer.camera.flyTo({
    destination: Cesium.Cartesian3.fromDegrees(116.3860, 39.9000, 110),
    orientation: { heading: Cesium.Math.toRadians(26), pitch: Cesium.Math.toRadians(-12), roll: 0 },
    duration: 0
  });
})();
</script>
</body>
</html>