code: public void setScene(GVRScene scene)
      {
          mPicker.setScene(scene);
          if (scene != null)
          {
              synchronized (mCursorLock)
              {
                  if (mDragRoot.getParent() != null)
                  {
                      mDragRoot.getParent().removeChildObject(mDragRoot);
                  }
                  scene.getMainCameraRig().addChildObject(mDragRoot);
              }
          }
          this.scene = scene;
      }
docs: Change the scene associated with this controller (and
  its associated picker). The picker is not enabled
  and will not automatically pick. The controller
  explicity calls GVRPicker.processPick each tima a
  controller event is received.
  @param scene The scene from which to pick colliders