title: Can't add a 3D subview to the view of the controller
body: <p>I have a problem when i want to add a 3D subview to my controller view. I can't see the 3D subview. Is the code of GameControllerView class :</p>
  
  <pre><code>override func viewDidLoad() {
      super.viewDidLoad()
  
      println("Start the game")
  
      // Model
      cubeData = CubeData()
      /*
      let viewTest = UIView(frame: self.view.frame)
      self.view = viewTest
      */
  
      // 3D view position
      let sizeScnView = CGSize(width: 350.0, height: 350.0)
      let centerView = CGPoint(x: CGRectGetMidX(self.view.frame) - sizeScnView.width/2, y: CGRectGetMidY(self.view.frame) - sizeScnView.height/2)
      scnView = GameSceneView(frame: CGRect(origin: centerView, size: sizeScnView))
  
      // add 3D view
      self.view.addSubview(scnView)
  
      // don't allows the user to manipulate the camera
      scnView.allowsCameraControl = true
  
      // show statistics such as fps and timing information
      scnView.showsStatistics = false
  
      // Start Accelerometer
      self.motionManager = CMMotionManager()
      self.startAccelerometer()
  
      timer = NSTimer.scheduledTimerWithTimeInterval(0.4, target: self, selector: Selector("updateTimer"), userInfo: nil, repeats: true)
  }
  </code></pre>
  
  <p>With this code i can't see my GameSceneView which is a subclass of SCNView (3D view). But if I delete comments of the viewTest variable (just below cubeData) my GameSceneView is displayed but without the content of my controller view.</p>
  
  <p>Question : Why 3D subview can't appear on the controller view ?</p>
  
  <p>EDIT : I just noticed that the 3D view is behind the controller view background. How can I add my 3D view over the background contained in view controller ?</p>