title: ARKit Session Paused and Not Resuming
body: <p>In my ARKit app I am presenting a modal window. When I close the modal and go back to the ARSCNView then I find out that the session is paused due to this code: </p>
  
  <pre><code> override func viewWillDisappear(_ animated: Bool) {
          super.viewWillDisappear(animated)
  
          // Pause the view's session
          sceneView.session.pause()
      } 
  </code></pre>
  
  <p>When I close the modal and go back to the ARKit camera view screen this code gets fired: </p>
  
  <pre><code>override func viewWillAppear(_ animated: Bool) {
          super.viewWillAppear(animated)
  
          // Create a session configuration
          let configuration = ARWorldTrackingSessionConfiguration()
  
          // Run the view's session
          sceneView.session.run(configuration)
      }
  </code></pre>
  
  <p>But this code never resumes the session. The screen is completely frozen on the last image it read. Any ideas?</p>
  
  <p>I update the viewDidAppear code to be the following. It is still stuck on the camera screen with image frozen.  </p>
  
  <pre><code>  override func viewWillAppear(_ animated: Bool) {
          super.viewWillAppear(animated)
  
          // Create a session configuration
          let configuration = ARWorldTrackingSessionConfiguration()
  
          sceneView.session.delegate = self
  
          if self.isPaused {
              sceneView.session.run(sceneView.session.configuration!)
          } else {
              // Run the view's session
              sceneView.session.run(configuration)
          }
  
  
      }
  </code></pre>