Parallels and Meridians

<!--
  示例：经纬网
  说明：每 15 度画一条纬线与经线，贴在地球表面形成网格
  核心逻辑：循环生成纬度/经度顶点 → polyline clampToGround → 两极处经线收拢
  依赖：CesiumJS 1.121 · jsDelivr CDN
-->
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<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>经纬网</title>
<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/cesium@1.121.0/Build/Cesium/Widgets/widgets.css">
<style>
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       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}

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  .cesium-viewer-timelineContainer{display:none!important}
</style>
</head>
<body>
<div id="c"></div>
<div class="tip">纬线是等纬度采样，经线在极点附近会收成一点。</div>
<script src="https://cdn.jsdelivr.net/npm/cesium@1.121.0/Build/Cesium/Cesium.js"></script>
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  'use strict';

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    animation: false, timeline: false, fullscreenButton: false,
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  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;

  function meridian(lon, color) {
    var pts = [];
    for (var lat = -80; lat <= 80; lat += 4) {
      pts.push(lon, lat);
    }
    viewer.entities.add({
      polyline: {
        positions: Cesium.Cartesian3.fromDegreesArray(pts),
        width: 1.6,
        clampToGround: true,
        material: Cesium.Color.fromCssColorString(color).withAlpha(0.75)
      }
    });
  }

  function parallel(lat, color) {
    var pts = [];
    for (var lon = -180; lon <= 180; lon += 4) {
      pts.push(lon, lat);
    }
    viewer.entities.add({
      polyline: {
        positions: Cesium.Cartesian3.fromDegreesArray(pts),
        width: 1.6,
        clampToGround: true,
        material: Cesium.Color.fromCssColorString(color).withAlpha(0.75)
      }
    });
  }

  for (var lon = -180; lon < 180; lon += 15) { meridian(lon, '#4d86c8'); }
  for (var lat = -75; lat <= 75; lat += 15) { parallel(lat, '#8fb4d8'); }

  /* 赤道加粗 */
  parallel(0, '#d08a4e');
  viewer.camera.flyTo({
    destination: Cesium.Cartesian3.fromDegrees(105, 30, 21000000),
    orientation: { heading: 0, pitch: Cesium.Math.toRadians(-90), roll: 0 },
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  });
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