title: autodesk-forge Creating 3d forge viwer using both 2 legged and 3 legged authorization
body: <p>I am developing an app using forge viewer API. Currently, we are displaying 3d model stored in my own bucket, for that we are using only 2 legged token Oauth. </p>
  
  <p>Some of our clients are using BIM360 document, so we got their model URNs by using document derivatives API and we set up the viewer with this URN. The method is similar to the following: <a href="https://stackoverflow.com/questions/37835178/creating-a-viewer-application-with-an-urn-from-autodesk-a360">Creating a viewer application with an URN from Autodesk A360</a> but with BIM360.</p>
  
  <p>I implemented 3 legged token Oauth for using forge viewer with this kind of URN. Both authorization methods are used, so I would like to find a way to manage token workflow. To ask or test if I need 2 or 3 legged tokens. </p>
  
  <ul>
  <li>Do there is a request to know the authentification required to read an urn with forge viewer? </li>
  </ul>
  
  <p>Also, I tried to display URN from BIM360 document and I noticed that do not need a 3 legged token, after all, just a 2 legged token is necessary. </p>
  
  <ul>
  <li>Do you know why? </li>
  </ul>