title: Autodesk Forge: Measurement and Slice not working - Not an instance of THREE.Object3D
body: <p>I have created a Forge Viewer using version 7 of the viewer3d.js and can view a model within it.</p>
  
  <p>My issue is that the measurement and slice tools aren't working as expected. 
  FYI I'm using typescript - angular 8.</p>
  
  <p>I'm expecting the graphics to look like this for a slice:</p>
  
  <p><a href="https://i.stack.imgur.com/ZvkAl.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/ZvkAl.png" alt="enter image description here"></a></p>
  
  <p>Instead the plane and gyroscope symbol never appear:
  <a href="https://i.stack.imgur.com/rZ3zR.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/rZ3zR.png" alt="enter image description here"></a></p>
  
  <p>Similarly with the measurement tool, the mouse cursor changes to the measurement cursor, but when i click on a surface, nothing happens.</p>
  
  <p>Here is my code for loading the viewer:</p>
  
  <pre><code>  loadViewer(forgeTokenData, modelUrn) {
  
  
      options = {
        env: 'AutodeskProduction',
        api: 'derivativeV2',
        getAccessToken: (onSuccess) =&gt; {
          onSuccess((forgeTokenData as any).access_token, (forgeTokenData as any).expires_in);
      }};
  
      Autodesk.Viewing.Initializer(options, () =&gt; {
  
        // Find the element where the 3d viewer will live.
        const htmlElement = document.getElementById('viewerContainer');
  
        if (htmlElement) {
          // Create and start the viewer in that element
          const viewer = new Autodesk.Viewing.GuiViewer3D(htmlElement);
          viewer.start();
  
          const documentId = 'urn:' + this.removeBase64Padding(modelUrn);
  
          console.log(documentId);
  
          this.loadDocument(documentId, viewer);
        }});
    }
  </code></pre>
  
  <p>I've also loaded the styles and scripts in my index.html head:</p>
  
  <pre><code>&lt;head&gt;
    &lt;meta charset="utf-8"&gt;
    &lt;title&gt;testing&lt;/title&gt;
    &lt;base href="/"&gt;
    &lt;meta name="viewport" content="width=device-width, initial-scale=1"&gt;
    &lt;link rel="icon" type="image/x-icon" href="favicon.ico"&gt;
    &lt;link rel="stylesheet" href="https://developer.api.autodesk.com/modelderivative/v2/viewers/7.*/style.min.css" type="text/css"&gt;
    &lt;script src="https://developer.api.autodesk.com/modelderivative/v2/viewers/7.*/viewer3D.min.js" &gt;&lt;/script&gt;
  &lt;/head&gt;
  </code></pre>
  
  <p>Not sure why this is happening. Are there any other styles or scripts i'm missing?</p>
  
  <p>I've noticed these errors in the console when i click on the slice / measurement tool:</p>
  
  <p><a href="https://i.stack.imgur.com/krMpp.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/krMpp.png" alt="enter image description here"></a></p>