Procedural Terrain

<!--
  示例：程序化地形
  说明：用噪声叠加生成起伏地形，山脊与谷地清晰，相机低角度观察
  核心逻辑：CustomHeightmapTerrainProvider → 多尺度正弦叠加 → 低角度相机
  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>程序化地形</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">地形高度全部由函数算出，没有请求任何地形服务。</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 SIZE = 64;

  function heightAt(u, v) {
    var h = 0;
    h += 220 * Math.sin(u * 1.7) * Math.cos(v * 1.3);
    h += 90 * Math.sin(u * 4.1 + 1.2) * Math.cos(v * 3.7);
    h += 34 * Math.sin(u * 9.3) * Math.sin(v * 8.1);
    return h;
  }

  var terrain = new Cesium.CustomHeightmapTerrainProvider({
    width: SIZE,
    height: SIZE,
    callback: function (x, y, level) {
      var heights = new Float32Array(SIZE * SIZE);
      for (var j = 0; j < SIZE; j++) {
        for (var i = 0; i < SIZE; i++) {
          heights[j * SIZE + i] = heightAt(x + i / SIZE * 0.02, y + j / SIZE * 0.02);
        }
      }
      return heights;
    }
  });
  viewer.terrainProvider = terrain;

  /* 山脊线标出三个采样点，贴地显示 */
  [-0.004, 0, 0.004].forEach(function (dLon) {
    viewer.entities.add({
      position: Cesium.Cartesian3.fromDegrees(116.3895 + dLon, 39.9035),
      point: {
        pixelSize: 8,
        color: Cesium.Color.fromCssColorString('#ffb13d'),
        heightReference: Cesium.HeightReference.CLAMP_TO_GROUND,
        disableDepthTestDistance: Number.POSITIVE_INFINITY
      }
    });
  });
  viewer.camera.flyTo({
    destination: Cesium.Cartesian3.fromDegrees(116.3795, 39.8960, 1300),
    orientation: { heading: Cesium.Math.toRadians(35), pitch: Cesium.Math.toRadians(-8), roll: 0 },
    duration: 0
  });
})();
</script>
</body>
</html>