three.js/src/core/Face3.js

/**
 * @author mrdoob / http://mrdoob.com/
 * @author alteredq / http://alteredqualia.com/
 */

THREE.Face3 = function ( a, b, c, normal, color, materialIndex ) {

	this.a = a;
	this.b = b;
	this.c = c;

	this.normal = normal instanceof THREE.Vector3 ? normal : new THREE.Vector3();
	this.vertexNormals = Array.isArray( normal ) ? normal : [];

	this.color = color instanceof THREE.Color ? color : new THREE.Color();
	this.vertexColors = Array.isArray( color ) ? color : [];

	this.materialIndex = materialIndex !== undefined ? materialIndex : 0;

};

THREE.Face3.prototype = {

	constructor: THREE.Face3,

	clone: function () {

		return new this.constructor().copy( this );

	},

	copy: function ( source ) {

		this.a = source.a;
		this.b = source.b;
		this.c = source.c;

		this.normal.copy( source.normal );
		this.color.copy( source.color );

		this.materialIndex = source.materialIndex;

		for ( var i = 0, il = source.vertexNormals.length; i < il; i ++ ) {

			this.vertexNormals[ i ] = source.vertexNormals[ i ].clone();

		}

		for ( var i = 0, il = source.vertexColors.length; i < il; i ++ ) {

			this.vertexColors[ i ] = source.vertexColors[ i ].clone();

		}

		return this;

	}

};