摘要：現在讓我們修改這個示例讓他可以展示兩個同項目但不同版號的模型及。示例執行結果如下這邊是這個比較模型的括展代碼英文原文

熟悉 BIM360 Team 的朋友可能知道他有一個很牛的模型文檔版本比較的功能，但如果模型是放在 Google 云盤或是百度云盤上有可能做到嗎？

Autodesk Forge 團隊先前寫了一個從 Google 云盤的轉檔示例，這個示例會從 Google 云盤里下載模型文檔到你的服務器上，在將它上傳到 Forge Data Management 服務上進行轉檔，同時在轉檔完成后在瀏覽器上展示結果。

現在讓我們修改這個示例讓他可以展示兩個同項目但不同版號的 Revit 模型（model A 及 model B）。在 Forge Viewer 里，每個 Revit 構件都會對應到一個 dbId，而這個 dbId 也會對應到一個 Reivt 唯一碼（Unique GUID），這個唯一碼也是 Forge Viewer 的外部編碼（Extenal Id），所以只要在 model A 及 model B 里比對兩者間有沒有不存在的 Extenal Id，以及比對同一個 External Id 的構件屬性里有沒有被新增、修改及刪除的參數，根據這個思路我們可以將沒有修改的構件隱藏起來，有異動的構件以綠色（新增的）、紅色（刪除的）及橘色（有修改的）來上色，就可以在 Forge Viewer 上做出簡單的模型比較功能，原代碼可以參考這里，示例可造訪這里。

示例執行結果如下：

這邊是這個比較模型的括展代碼：

function VersionChanges(viewer, options) {
  Autodesk.Viewing.Extension.call(this, viewer, options);
}

VersionChanges.prototype = Object.create(Autodesk.Viewing.Extension.prototype);
VersionChanges.prototype.constructor = VersionChanges;

VersionChanges.prototype.load = function () {
  var modelA = this.options.modelA;
  var modelB = this.options.modelB;

  var removed = {};
  var added = {};
  var modified = {};

  var red = new THREE.Vector4(1, 0, 0, 1);
  var green = new THREE.Vector4(0, 0.5, 0, 1);
  var orange = new THREE.Vector4(1, 0.6, 0.2, 1);

  viewer.addEventListener(Autodesk.Viewing.OBJECT_TREE_CREATED_EVENT, function () {
    listElements(function (listA, listB) {
      // make all elements as ghost
      viewer.isolate(-1);
      viewer.clearThemingColors(modelA);
      viewer.clearThemingColors(modelB);

      for (var extIdA in listA) {
        if (listB[extIdA] != null) continue;
        var dbIdA = listA[extIdA].dbId;
        removed[extIdA] = dbIdA;
        console.log("Removed dbId: " + dbIdA);
        viewer.impl.visibilityManager.show(dbIdA, modelA);
        viewer.setThemingColor(dbIdA, red, modelA);
      }

      for (var extIdB in listB) {
        if (listA[extIdB] != null) continue;
        var dbIdB = listB[extIdB].dbId
        added[extIdB] = dbIdB;
        console.log("Added dbId: " + dbIdB);
        viewer.impl.visibilityManager.show(dbIdB, modelB);
        viewer.setThemingColor(dbIdB, green, modelB);
      }

      for (var extId in listA) {
        if (typeof listB[extId] === "undefined") continue; // removed dbId

        var dbId = listA[extId].dbId; // should be the same as listB[extId]
        var propsA = listA[extId].properties;
        var propsB = listB[extId].properties;

        for (var i = 0; i < propsA.length; i++) {
          if (propsB[i] == null) continue;
          if (propsA[i].displayCategory.indexOf("__")==0) continue; // internal properties
          if (propsA[i].displayValue != propsB[i].displayValue) {
            console.log("Property " + dbId + ": " + propsA[i].displayName + " changed from "
              + propsA[i].displayValue + " to " + propsB[i].displayValue);
            modified[extId] = dbId;
          }
        }

        if (typeof modified[extId] != "undefined") {
          console.log("Modified dbId: " + dbId);
          // color on both models
          //viewer.impl.visibilityManager.show(dbId, modelA);
          //viewer.impl.visibilityManager.show(dbId, modelB);
          viewer.setThemingColor(dbId, orange, modelA);
          viewer.setThemingColor(dbId, orange, modelB);
        }
      }
    });
  });

  function listElements(callback) {
    getAllLeafComponents(modelA, function (modelAdbIds) {
      getAllLeafComponents(modelB, function (modelBdbIds) {
        // this count will help wait until getProperties end all callbacks
        var count = modelAdbIds.length + modelBdbIds.length;

        var modelAExtIds = {};
        modelAdbIds.forEach(function (modelAdbId) {
          modelA.getProperties(modelAdbId, function (modelAProperty) {
            modelAExtIds[modelAProperty.externalId] = {"dbId": modelAdbId, "properties": modelAProperty.properties};
            count--;
            if (count == 0) callback(modelAExtIds, modelBExtIds);
          });
        });

        var modelBExtIds = {};
        modelBdbIds.forEach(function (modelBdbId) {
          modelB.getProperties(modelBdbId, function (modelBProperty) {
            modelBExtIds[modelBProperty.externalId] = {"dbId": modelBdbId, "properties": modelBProperty.properties};
            count--;
            if (count == 0) callback(modelAExtIds, modelBExtIds);
          });
        });
      });
    });
  }


  function getAllLeafComponents(model, callback) {
    var components = [];

    function getLeafComponentsRec(tree, parentId) {
      if (tree.getChildCount(parentId) > 0) {
        tree.enumNodeChildren(parentId, function (childId) {
          getLeafComponentsRec(tree, childId);
        });
      }
      else
        components.push(parentId);
      return components;
    }

    var instanceTree = model.getInstanceTree();
    var allLeafComponents = getLeafComponentsRec(instanceTree, instanceTree.nodeAccess.rootId);
    callback(allLeafComponents);
  }

  return true;
};

VersionChanges.prototype.unload = function () {
  return true;
};

Autodesk.Viewing.theExtensionManager.registerExtension("Autodesk.Forge.Samples.VersionChanges", VersionChanges);

英文原文：https://forge.autodesk.com/bl...