3D Tiles BIM【译】

原文链接及内容

原文链接：https://sandcastle.cesium.com/?src=3D%20Tiles%20BIM.html&label=All

注： 由于个人的Cesium Ion中没有官方示例中的数据，因此仅在官方提供的在线编辑器中进行了学习、修改。

实现效果如下视频所示：

示例代码如下：

<style>
  @import url(../templates/bucket.css);
  .cesium-performanceDisplay-defaultContainer {
    top: 10px;
  }
</style>
<div id="cesiumContainer" class="fullSize"></div>
<div id="loadingOverlay"><h1>拼命加载数据中</h1></div>
<div id="toolbar"></div>

/**
 * 发电厂设计模型由 Bentley 软件公司提供
 */
const viewer = new Cesium.Viewer("cesiumContainer", {
  geocoder: false,
  homeButton: false,
  sceneModePicker: false,
  baseLayerPicker: false,
  navigationHelpButton: false,
  navigationInstructionsInitiallyVisible: false,
  animation: false,
  timeline: false,
  fullscreenButton: false,
  selectionIndicator: false,
  skyBox: false,
  shouldAnimate: true,
});

const scene = viewer.scene;

viewer.cesiumWidget.creditContainer.style.display = "none"; //隐藏版权信息
scene.debugShowFramesPerSecond = true; //添加帧速显示

viewer.clock.currentTime = Cesium.JulianDate.fromIso8601("2022-08-01T00:00:00Z");

let selectedFeature;
let picking = false;

Sandcastle.addToggleButton("按单个要素选择", false, function (checked) {
  picking = checked;
  if (!picking) {
    unselectFeature(selectedFeature);
  }
});

function selectFeature(feature) {
  const element = feature.getProperty("element");
  setElementColor(element, Cesium.Color.YELLOW);
  selectedFeature = feature;
}

function unselectFeature(feature) {
  if (!Cesium.defined(feature)) {
    return;
  }
  const element = feature.getProperty("element");
  setElementColor(element, Cesium.Color.WHITE);
  if (feature === selectedFeature) {
    selectedFeature = undefined;
  }
}

const handler = new Cesium.ScreenSpaceEventHandler(scene.canvas);
handler.setInputAction(function (movement) {
  if (!picking) {
    return;
  }

  const feature = scene.pick(movement.endPosition);

  unselectFeature(selectedFeature);

  if (feature instanceof Cesium.Cesium3DTileFeature) {
    selectFeature(feature);
  }
}, Cesium.ScreenSpaceEventType.MOUSE_MOVE);

/**
 * 在该数据集中，每个要素都有一个“element”属性，它是一个全局ID，
 * 该属性用于在不同瓦片和LOD（Levels of Detail，多细节层次）之间关联要素。
 * 这是在 3D Tiles 支持全局批次 ID 概念之前的一种临时解决方案：https://github.com/CesiumGS/3d-tiles/issues/265
 * 
 * 多细节层次 —— 在显示网格时，根据摄像机距离物体的距离，来使用更多或者更少的几何体来对其进行显示。
 * 详见：https://threejs.org/docs/#api/zh/objects/LOD
 */
const elementMap = {}; // 构建一个element属性到要素的映射。
const hiddenElements = [
  112001, 113180, 131136, 113167, 71309, 109652, 111178, 113156, 113170, 124846,
  114076, 131122, 113179, 114325, 131134, 113164, 113153, 113179, 109656, 114095,
  114093, 39225, 39267, 113149, 113071, 112003, 39229, 113160, 39227, 39234,
  113985, 39230, 112004, 39223,
];

function getElement(feature) {
  return parseInt(feature.getProperty("element"), 10);
}

function setElementColor(element, color) {
  const featuresToColor = elementMap[element];
  const length = featuresToColor.length;
  for (let i = 0; i < length; ++i) {
    const feature = featuresToColor[i];
    feature.color = Cesium.Color.clone(color, feature.color);
  }
}

function unloadFeature(feature) {
  unselectFeature(feature);
  const element = getElement(feature);
  const features = elementMap[element];
  const index = features.indexOf(feature);
  if (index > -1) {
    features.splice(index, 1);
  }
}

function loadFeature(feature) {
  const element = getElement(feature);
  let features = elementMap[element];
  if (!Cesium.defined(features)) {
    features = [];
    elementMap[element] = features;
  }
  features.push(feature);

  if (hiddenElements.indexOf(element) > -1) {
    feature.show = false;
  }
}

function processContentFeatures(content, callback) {
  const featuresLength = content.featuresLength;
  for (let i = 0; i < featuresLength; ++i) {
    const feature = content.getFeature(i);
    callback(feature);
  }
}

function processTileFeatures(tile, callback) {
  const content = tile.content;
  const innerContents = content.innerContents;
  if (Cesium.defined(innerContents)) {
    const length = innerContents.length;
    for (let i = 0; i < length; ++i) {
      processContentFeatures(innerContents[i], callback);
    }
  } else {
    processContentFeatures(content, callback);
  }
}

try {
  const tileset = await Cesium.Cesium3DTileset.fromIonAssetId(2464651);
  scene.primitives.add(tileset);

  viewer.zoomTo(
    tileset,
    new Cesium.HeadingPitchRange(0.5, -0.2, tileset.boundingSphere.radius * 4.0),
  );

  tileset.colorBlendMode = Cesium.Cesium3DTileColorBlendMode.REPLACE;
  tileset.tileLoad.addEventListener(function (tile) {
    processTileFeatures(tile, loadFeature);
  });

  tileset.tileUnload.addEventListener(function (tile) {
    processTileFeatures(tile, unloadFeature);
  });
} catch (err) {
  ElMessage.error(`tileset数据加载出错: ${err}`);
}