Cartographic Limit Rectangle

<!--
  示例：用 cartographicLimitRectangle 只渲染一块经纬度范围
  说明：球体被裁成一块矩形，范围外的地表不绘制，实体不受影响
  核心逻辑：globe.cartographicLimitRectangle = Rectangle.fromDegrees(...) → 相机俯视
  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>限定球体显示范围</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%}
  .hud{position:absolute;left:12px;top:12px;z-index:5;background:rgba(23,28,35,.9);
       border:1px solid #2a313b;border-radius:6px;padding:9px 12px;font-size:12px;
       color:#a2a9b6;max-width:260px}
  .hud b{color:#e6e8ec;font-weight:600}
  .hud .row{margin-top:7px}
  .cesium-viewer-bottom .cesium-widget-credits,.cesium-viewer-animationContainer,
  .cesium-viewer-timelineContainer{display:none!important}
</style>
</head>
<body>
<div id="c"></div>
<div class="hud">
  <div><b>限定显示范围</b></div>
  <div class="row">东经 105°–122°，北纬 25°–42°</div>
  <div class="row"><label><input id="limit" type="checkbox" checked> 启用裁剪</label></div>
  <div class="row">范围外的地表变成背景色</div>
</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;
  var globe = scene.globe;
  globe.baseColor = Cesium.Color.fromCssColorString('#1c2733');
  scene.backgroundColor = Cesium.Color.fromCssColorString('#080c12');
  scene.skyBox.show = false;
  scene.sun.show = false;
  scene.moon.show = false;
  if (scene.skyAtmosphere) scene.skyAtmosphere.show = false;

  var belt = Cesium.Rectangle.fromDegrees(105, 25, 122, 42);
  globe.cartographicLimitRectangle = belt;

  /* 球面上放几个点，验证它们不会被裁掉 */
  var cities = [
    [116.391, 39.907, '北京'],
    [121.473, 31.230, '上海'],
    [113.264, 23.129, '广州'],
    [104.066, 30.572, '成都']
  ];

  cities.forEach(function (c) {
    viewer.entities.add({
      position: Cesium.Cartesian3.fromDegrees(c[0], c[1], 0),
      point: {
        pixelSize: 9,
        color: Cesium.Color.fromCssColorString('#4d9bff'),
        outlineColor: Cesium.Color.WHITE,
        outlineWidth: 2,
        disableDepthTestDistance: Number.POSITIVE_INFINITY
      },
      label: {
        text: c[2],
        font: '500 12px "Microsoft YaHei", sans-serif',
        fillColor: Cesium.Color.WHITE,
        pixelOffset: new Cesium.Cartesian2(0, -20),
        disableDepthTestDistance: Number.POSITIVE_INFINITY
      }
    });
  });

  document.getElementById('limit').addEventListener('change', function () {
    globe.cartographicLimitRectangle = this.checked ? belt : undefined;
  });

  viewer.camera.flyTo({
    destination: Cesium.Cartesian3.fromDegrees(113, 33, 9200000),
    orientation: {
      heading: 0,
      pitch: Cesium.Math.toRadians(-72),
      roll: 0
    },
    duration: 0
  });
})();
</script>
</body>
</html>