Distance Display Conditions

<!--
  示例：按距离显示
  说明：三个标签各自只在指定距离区间内出现，缩放到不同高度看到不同标注
  核心逻辑：DistanceDisplayCondition(near, far) → 标签 / 点 / 面均可设置
  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>按距离显示</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">滚轮缩放画面，近、中、远三个标签会在各自的距离区间里出现。</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 pos = Cesium.Cartesian3.fromDegrees(116.390, 39.904, 40);

  var tiers = [
    { near: 0, far: 900, text: '近景：街区', color: '#4d9bff' },
    { near: 900, far: 2600, text: '中景：城区', color: '#5bb08a' },
    { near: 2600, far: 9000, text: '远景：市域', color: '#d08a4e' }
  ];

  tiers.forEach(function (t) {
    viewer.entities.add({
      position: pos,
      point: {
        pixelSize: 10,
        color: Cesium.Color.fromCssColorString(t.color),
        distanceDisplayCondition: new Cesium.DistanceDisplayCondition(t.near, t.far)
      },
      label: {
        text: t.text,
        font: '600 14px sans-serif',
        fillColor: Cesium.Color.fromCssColorString(t.color),
        pixelOffset: new Cesium.Cartesian2(0, -22),
        distanceDisplayCondition: new Cesium.DistanceDisplayCondition(t.near, t.far),
        disableDepthTestDistance: Number.POSITIVE_INFINITY
      }
    });
  });

  /* 相机停在中距离，只看到中景标签 */
  viewer.camera.flyTo({
    destination: Cesium.Cartesian3.fromDegrees(116.390, 39.897, 1600),
    orientation: { heading: 0, pitch: Cesium.Math.toRadians(-28), roll: 0 },
    duration: 0
  });
  /* 相机已在正文中设置 */
})();
</script>
</body>
</html>