I3s Feature Picking

<!--
  示例：要素拾取与高亮
  说明：点击任意楼栋，被点的那栋变色并在右上角显示 ID
  核心逻辑：scene.pick → 按 id 匹配要素 → 改材质并恢复上一次高亮
  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>要素拾取与高亮</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}

  .info{position:absolute;right:12px;top:12px;background:rgba(23,28,35,.92);
        border:1px solid #2a313b;border-radius:6px;padding:8px 12px;font-size:12px;color:#cfe2f5}
  .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">点击楼栋会高亮它并恢复上一栋的颜色，同一时刻只有一栋被选中。</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 items = [];
  var palette = ['#4f5f74', '#596a80', '#63758c', '#6d8098'];

  for (var i = 0; i < 9; i++) {
    for (var j = 0; j < 6; j++) {
      var h = 22 + ((i * 5 + j * 7) % 7) * 8;
      var color = palette[(i + j) % palette.length];
      var e = viewer.entities.add({
        position: Cesium.Cartesian3.fromDegrees(
          116.3856 + i * 0.00086, 39.9020 + j * 0.00080, h / 2
        ),
        box: {
          dimensions: new Cesium.Cartesian3(28, 26, h),
          material: Cesium.Color.fromCssColorString(color).withAlpha(0.95),
          outline: true,
          outlineColor: Cesium.Color.fromCssColorString('#0b0f14')
        }
      });
      items.push({ entity: e, color: color, id: 'building-' + i + '-' + j });
    }
  }

  var info = document.createElement('div');
  info.className = 'info';
  info.style.display = 'none';
  document.body.appendChild(info);

  var last = null;
  var handler = new Cesium.ScreenSpaceEventHandler(scene.canvas);
  handler.setInputAction(function (click) {
    var picked = scene.pick(click.position);
    if (last) {
      last.entity.box.material = Cesium.Color.fromCssColorString(last.color).withAlpha(0.95);
      last = null;
    }
    if (!Cesium.defined(picked) || !picked.id) { info.style.display = 'none'; return; }

    var hit = items.filter(function (it) { return it.entity === picked.id; })[0];
    if (!hit) return;
    hit.entity.box.material = Cesium.Color.fromCssColorString('#ffb13d');
    last = hit;
    info.style.display = 'block';
    info.textContent = hit.id + ' · 高 ' + Math.round(hit.entity.box.dimensions.getValue().z) + ' 米';
  }, Cesium.ScreenSpaceEventType.LEFT_CLICK);
  viewer.camera.flyTo({
    destination: Cesium.Cartesian3.fromDegrees(116.3944, 39.8988, 300),
    orientation: { heading: Cesium.Math.toRadians(18), pitch: Cesium.Math.toRadians(-20), roll: 0 },
    duration: 0
  });
})();
</script>
</body>
</html>