traverseAncestors( callback ) {

		const parent = this.parent;

		if ( parent !== null ) {

			callback( parent );

			parent.traverseAncestors( callback );

		}

	}
Like {@link Object3D#traverse}, but the callback will only be executed for all ancestors.

Note: Modifying the scene graph inside the callback is discouraged.

@param {Function} callback - A callback function that allows to process the current 3D object.