_updateSelectionCache() {

		for ( let i = 0; i < this.selectedObjects.length; i ++ ) {

			const selectedObject = this.selectedObjects[ i ];
			selectedObject.traverse( ( object ) => {

				if ( object.isMesh ) this._selectionCache.add( object );

			} );

		}

	}
Updates the selection cache based on the selected objects.

@private