title: How to Retrieve Forge Viewer objectTree?
body: <p>My goal is to highlight a room by adding new geometry to the viewer based on lines I have created in revit like they do here <a href="http://thebuildingcoder.typepad.com/blog/2016/06/highlighting-revit-rooms-in-the-forge-viewer.html#4" rel="nofollow">Link</a></p>
  
  <p>but i can not figure out how to access those lines ids.
  I know what they are in revit (element_id) but not how they are mapped as dbid.</p>
  
  <p>Following this <a href="http://adndevblog.typepad.com/cloud_and_mobile/2015/12/select-all-elements-in-the-viewer-with-view-and-data-api-with-javascript.html" rel="nofollow">Blog Post</a></p>
  
  <p>I want to access the objectTree in my extension to find out, but it always comes back as undefined.</p>
  
  <pre><code>var tree;
  //old way - viewer is your viewer object - undefined
  viewer.getObjectTree(function (objTree) {
   tree = objTree;
  });
  </code></pre>
  
  <p>//2.5 - undefined</p>
  
  <pre><code>  var instanceTree = viewer.model.getData().instanceTree;
    var rootId = this.rootId = instanceTree.getRootId();
  </code></pre>
  
  <p>//- undefined</p>
  
  <pre><code>  var objectTree = viewer.getObjectTree();
  </code></pre>
  
  <p>Can anyone tell me if its still works for them I am using the v2 of the API for the rvt conversion to svf and 2.9 of the viewer3D.js</p>
  
  <p>note I can see a list of dbid if I call this</p>
  
  <pre><code>var model = viewer.impl.model;
  var data = model.getData();
  var fragId2dbIdArray = data.fragments.fragId2dbId ;
  </code></pre>
  
  <p>but have no way of mapping back to the Revit element_id</p>