GeoJSON and Topojson

<!--
  示例：GeoJSON 与 TopoJSON
  说明：同一片区域分别用 GeoJSON 与 TopoJSON 表达，加载后形状一致
  核心逻辑：GeoJsonDataSource.load(对象) → 共享边界压缩 → 样式统一
  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>GeoJSON 与 TopoJSON</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">左边来自 GeoJSON，右边来自 TopoJSON，两者的几何是同一个形状。</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;

  /* GeoJSON：每个多边形独立存坐标 */
  var geojson = {
    type: 'FeatureCollection',
    features: [{
      type: 'Feature',
      properties: { name: 'GeoJSON 面' },
      geometry: {
        type: 'Polygon',
        coordinates: [[
          [116.3830, 39.9010], [116.3870, 39.9010],
          [116.3870, 39.9040], [116.3830, 39.9040],
          [116.3830, 39.9010]
        ]]
      }
    }]
  };

  /* TopoJSON：共享边界存成 arcs，按索引引用 */
  var topojson = {
    type: 'Topology',
    objects: {
      blocks: {
        type: 'GeometryCollection',
        geometries: [{
          type: 'Polygon',
          arcs: [[0]],
          properties: { name: 'TopoJSON 面' }
        }]
      }
    },
    arcs: [[
      [0, 0], [40, 0], [0, 30], [-40, 0], [0, -30]
    ]],
    transform: { scale: [0.0001, 0.0001], translate: [116.3890, 39.9020] }
  };

  Cesium.GeoJsonDataSource.load(geojson, {
    clampToGround: true
  }).then(function (ds) {
    ds.entities.values.forEach(function (e) {
      if (e.polygon) e.polygon.material = Cesium.Color.fromCssColorString('#4d86c8').withAlpha(0.7);
    });
    viewer.dataSources.add(ds);
  });

  Cesium.GeoJsonDataSource.load(topojson, {
    clampToGround: true
  }).then(function (ds) {
    ds.entities.values.forEach(function (e) {
      if (e.polygon) e.polygon.material = Cesium.Color.fromCssColorString('#d08a4e').withAlpha(0.7);
    });
    viewer.dataSources.add(ds);
  });
  viewer.camera.flyTo({
    destination: Cesium.Cartesian3.fromDegrees(116.3895, 39.8988, 520),
    orientation: { heading: 0, pitch: Cesium.Math.toRadians(-42), roll: 0 },
    duration: 0
  });
})();
</script>
</body>
</html>