Layer Order

<!--
  示例：影像图层的顺序控制
  要点：三层程序生成的栅格叠在一起，raise/lower 调整索引，索引决定最终合成顺序
  依赖：CesiumJS 1.121 · jsDelivr CDN，GridImageryProvider 不请求任何瓦片
-->
<!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>图层顺序控制</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%}
  .hud{position:absolute;left:12px;top:12px;z-index:5;background:rgba(23,28,35,.9);
       border:1px solid #2a313b;border-radius:6px;padding:9px 12px;font-size:12px;
       color:#a2a9b6;max-width:268px}
  .hud b{color:#e6e8ec;font-weight:600}
  .hud .row{margin-top:6px}
  .layer{display:flex;align-items:center;gap:6px;margin-top:5px}
  .layer .name{flex:1 1 auto;color:#cfd6e2;font-size:12px}
  .hud button{font:inherit;font-size:11px;padding:2px 7px;border-radius:4px;cursor:pointer;
       border:1px solid #343b46;background:#1d232b;color:#cfd6e2}
  .hud button:hover{background:#262d37}
  input[type=range]{width:100%;margin-top:6px}
  .cesium-viewer-bottom .cesium-widget-credits,.cesium-viewer-animationContainer,
  .cesium-viewer-timelineContainer{display:none!important}
</style>
</head>
<body>
<div id="c"></div>
<div class="hud">
  <div><b>图层顺序</b><span style="color:#7f8899"> 上层优先</span></div>
  <div id="list"></div>
  <div class="row">整体透明度</div>
  <div class="row"><input id="alpha" type="range" min="0" max="1" step="0.05" value="1"></div>
</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('#0f1d29');
  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 BLUE = Cesium.Color.fromCssColorString('#4d9bff');
  var ORANGE = Cesium.Color.fromCssColorString('#ffb13d');
  var GREEN = Cesium.Color.fromCssColorString('#3fe0b0');

  function gridLayer(color, cells, alpha, name) {
    var layer = new Cesium.ImageryLayer(new Cesium.GridImageryProvider({
      color: color.withAlpha(0.65),
      glowColor: Cesium.Color.TRANSPARENT,
      backgroundColor: color.withAlpha(0.10),
      cells: cells,
      tileWidth: 256,
      tileHeight: 256
    }), { alpha: alpha });
    viewer.imageryLayers.add(layer);
    layer.__baseAlpha = alpha;
    layer.__name = name;
    return layer;
  }

  gridLayer(BLUE, 4, 0.55, '蓝色 4×4 网格');
  gridLayer(ORANGE, 8, 0.45, '橙色 8×8 网格');
  var numbering = new Cesium.ImageryLayer(new Cesium.TileCoordinatesImageryProvider({
    color: GREEN,
    backgroundColor: Cesium.Color.TRANSPARENT,
    tileWidth: 256,
    tileHeight: 256
  }), { alpha: 0.9 });
  viewer.imageryLayers.add(numbering);
  numbering.__baseAlpha = 0.9;
  numbering.__name = '瓦片行列号';

  function renderList() {
    var layers = viewer.imageryLayers;
    var box = document.getElementById('list');
    box.innerHTML = '';

    for (var i = layers.length - 1; i >= 0; i--) {
      (function (index) {
        var layer = layers.get(index);
        var row = document.createElement('div');
        row.className = 'layer';

        var name = document.createElement('span');
        name.className = 'name';
        name.textContent = (index + 1) + '. ' + layer.__name;
        row.appendChild(name);

        var up = document.createElement('button');
        up.textContent = '↑';
        up.title = '上移一层';
        up.addEventListener('click', function () {
          if (index < viewer.imageryLayers.length - 1) {
            viewer.imageryLayers.raise(layer);
            renderList();
          }
        });
        row.appendChild(up);

        var down = document.createElement('button');
        down.textContent = '↓';
        down.title = '下移一层';
        down.addEventListener('click', function () {
          if (index > 0) {
            viewer.imageryLayers.lower(layer);
            renderList();
          }
        });
        row.appendChild(down);

        var show = document.createElement('button');
        show.textContent = layer.show ? '隐藏' : '显示';
        show.addEventListener('click', function () {
          layer.show = !layer.show;
          renderList();
        });
        row.appendChild(show);

        box.appendChild(row);
      })(i);
    }
  }

  document.getElementById('alpha').addEventListener('input', function () {
    var k = parseFloat(this.value);
    var layers = viewer.imageryLayers;
    for (var i = 0; i < layers.length; i++) {
      layers.get(i).alpha = layers.get(i).__baseAlpha * k;
    }
  });

  renderList();

  viewer.camera.flyTo({
    destination: Cesium.Cartesian3.fromDegrees(105, 20, 20000000),
    orientation: { heading: 0, pitch: Cesium.Math.toRadians(-90), roll: 0 },
    duration: 0
  });
})();
</script>
</body>
</html>