three.js - split a (loaded) model into mesh parts by material index

gistfile1.js

	/**
	 * split a (loaded) model into mesh parts by material index
	 * @param {THREE.Geometry} geometry
	 * @param {Array<THREE.Material>} materials
	 * @returns {Array<THREE.Mesh>}
	 */
	var splitByMaterial = function(geometry,materials) {
		var parts = [],
			geo, vMap, iMat,
			addPart = function() {
				var mat = materials[iMat];
				mat.side = THREE.DoubleSide;
				parts.push(new THREE.Mesh(geo,mat));
			};
		geometry.faces.forEach(function(face) {
			if( face.materialIndex != iMat ) {
				if( iMat !== undefined )
					addPart();
				geo = new THREE.Geometry();
				vMap = {};
				iMat = face.materialIndex;
			}
			var f = face.clone();
			['a','b','c'].forEach(function(p) {
				var iv = face[p];
				if( !vMap.hasOwnProperty(iv) )
					vMap[iv] = geo.vertices.push(geometry.vertices[iv]) - 1;
				f[p] = vMap[iv];
			});
			geo.faces.push(f);
		});
		addPart();
		return parts;
	};