Globe Materials Water Mask Elevation Map

<!--
  示例：高程配色与水面
  说明：按高程渐变上色，低处偏蓝、高处偏白，再叠一层半透明水面
  核心逻辑：ElevationRamp + 渐变贴图 → 水面矩形 → 地形
  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>高程配色与水面</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">地表颜色由高程渐变决定，蓝色半透明面是海平面位置的水面。</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 heightAt(u, v) {
    return 160 * Math.sin(u * 1.9) * Math.cos(v * 1.5) + 50 * Math.cos(u * 4.2);
  }

  var terrain = new Cesium.CustomHeightmapTerrainProvider({
    width: 48, height: 48,
    callback: function (x, y, level) {
      var n = 48, h = new Float32Array(n * n);
      for (var j = 0; j < n; j++) {
        for (var i = 0; i < n; i++) {
          h[j * n + i] = heightAt(x + i / n * 0.03, y + j / n * 0.03);
        }
      }
      return h;
    }
  });
  viewer.terrainProvider = terrain;

  /* 一张竖直渐变条：低处蓝，高处浅 */
  function ramp() {
    var c = document.createElement('canvas');
    c.width = 16; c.height = 256;
    var ctx = c.getContext('2d');
    var g = ctx.createLinearGradient(0, 256, 0, 0);
    g.addColorStop(0, '#1c4f78');
    g.addColorStop(0.45, '#3f7a5c');
    g.addColorStop(0.75, '#8a8a58');
    g.addColorStop(1, '#eef2f6');
    ctx.fillStyle = g;
    ctx.fillRect(0, 0, 16, 256);
    return c.toDataURL('image/png');
  }

  scene.globe.material = Cesium.Material.fromType('ElevationRamp', {
    image: ramp(),
    minimumHeight: -120,
    maximumHeight: 240
  });

  /* 海平面：一块半透明的水面 */
  viewer.entities.add({
    rectangle: {
      coordinates: Cesium.Rectangle.fromDegrees(116.360, 39.870, 116.420, 39.930),
      height: 0,
      material: Cesium.Color.fromCssColorString('#2b6f9e').withAlpha(0.42)
    }
  });
  viewer.camera.flyTo({
    destination: Cesium.Cartesian3.fromDegrees(116.3740, 39.8840, 1100),
    orientation: { heading: Cesium.Math.toRadians(24), pitch: Cesium.Math.toRadians(-12), roll: 0 },
    duration: 0
  });
})();
</script>
</body>
</html>