docs: public void addChildObjectToCamera(final GVRSceneObject child, int camera) {
          switch (camera) {
              case LEFT_CAMERA:
                  mLeftCameraRootObject.addChildObject(child);
                  break;
              case RIGHT_CAMERA:
                  mRightCameraRootObject.addChildObject(child);
                  break;
              default:
                  mMainCameraRootObject.addChildObject(child);
                  break;
          }
      }