function createMeshesFromMultiMaterialMesh( mesh ) {

	if ( Array.isArray( mesh.material ) === false ) {

		console.warn( 'THREE.SceneUtils.createMeshesFromMultiMaterialMesh(): The given mesh has no multiple materials.' );
		return mesh;

	}

	const object = new Group();
	object.copy( mesh );

	// merge groups (which automatically sorts them)

	const geometry = mergeGroups( mesh.geometry );

	const index = geometry.index;
	const groups = geometry.groups;
	const attributeNames = Object.keys( geometry.attributes );

	// create a mesh for each group by extracting the buffer data into a new geometry

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

		const group = groups[ i ];

		const start = group.start;
		const end = start + group.count;

		const newGeometry = new BufferGeometry();
		const newMaterial = mesh.material[ group.materialIndex ];

		// process all buffer attributes

		for ( let j = 0; j < attributeNames.length; j ++ ) {

			const name = attributeNames[ j ];
			const attribute = geometry.attributes[ name ];
			const itemSize = attribute.itemSize;

			const newLength = group.count * itemSize;
			const type = attribute.array.constructor;

			const newArray = new type( newLength );
			const newAttribute = new BufferAttribute( newArray, itemSize );

			for ( let k = start, n = 0; k < end; k ++, n ++ ) {

				const ind = index.getX( k );

				if ( itemSize >= 1 ) newAttribute.setX( n, attribute.getX( ind ) );
				if ( itemSize >= 2 ) newAttribute.setY( n, attribute.getY( ind ) );
				if ( itemSize >= 3 ) newAttribute.setZ( n, attribute.getZ( ind ) );
				if ( itemSize >= 4 ) newAttribute.setW( n, attribute.getW( ind ) );

			}


			newGeometry.setAttribute( name, newAttribute );

		}

		const newMesh = new Mesh( newGeometry, newMaterial );
		object.add( newMesh );

	}

	return object;

}
This function creates a mesh for each geometry-group of the given multi-material mesh and
adds it to a group.

@param {Mesh} mesh - The multi-material mesh.
@return {Group} A group of meshes.