code: public void addChildObjectToCamera(final Widget child, int camera) {
          switch (camera) {
              case LEFT_CAMERA:
                  mLeftCameraRootWidget.addChild(child);
                  break;
              case RIGHT_CAMERA:
                  mRightCameraRootWidget.addChild(child);
                  break;
              default:
                  mMainCameraRootWidget.addChild(child);
                  break;
          }
      }
docs: Adds a scene object to one or both of the left and right cameras.
  
  @param child  The {@link Widget} to add.
  @param camera {@link #LEFT_CAMERA} or {@link #RIGHT_CAMERA}; these can be
  or'd together to add {@code child} to both cameras.