Earth At Night

<!--
  示例：夜光地球
  说明：深色底图上叠加城市灯光点，亮度被压暗，呈现夜间灯光分布
  核心逻辑：canvas 绘制暗底与灯点 → layer.brightness / gamma 压暗 → 球面夜景
  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>夜光地球</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">底图是代码绘制的夜光示意，城市灯点用高斯亮斑模拟。</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;

  function nightImage() {
    var W = 1600, H = 800;
    var c = document.createElement('canvas');
    c.width = W; c.height = H;
    var ctx = c.getContext('2d');
    ctx.fillStyle = '#05070c';
    ctx.fillRect(0, 0, W, H);

    /* 灯点：在东半球密集一些 */
    for (var i = 0; i < 1400; i++) {
      var x = W * (0.45 + 0.35 * Math.random());
      var y = H * (0.2 + 0.5 * Math.random());
      var r = 0.6 + Math.random() * 2.2;
      var g = ctx.createRadialGradient(x, y, 0, x, y, r * 4);
      g.addColorStop(0, 'rgba(255,228,170,0.95)');
      g.addColorStop(1, 'rgba(255,190,90,0)');
      ctx.fillStyle = g;
      ctx.beginPath();
      ctx.arc(x, y, r * 4, 0, Math.PI * 2);
      ctx.fill();
    }
    return c.toDataURL('image/png');
  }

  var layer = viewer.imageryLayers.addImageryProvider(
    new Cesium.SingleTileImageryProvider({
      url: nightImage(),
      rectangle: Cesium.Rectangle.fromDegrees(-180, -90, 180, 90),
      tileWidth: 1600,
      tileHeight: 800
    })
  );
  layer.brightness = 1.35;
  layer.gamma = 0.75;      /* 压暗暗部，让灯光更干净 */
  layer.contrast = 1.25;
  viewer.camera.flyTo({
    destination: Cesium.Cartesian3.fromDegrees(105, 32, 19000000),
    orientation: { heading: 0, pitch: Cesium.Math.toRadians(-90), roll: 0 },
    duration: 0
  });
})();
</script>
</body>
</html>