/**
 * @author mrdoob / http://mrdoob.com/
 * @author WestLangley / http://github.com/WestLangley
*/

THREE.FaceNormalsHelper = function ( object, size, hex, linewidth ) {

	this.object = object;

	this.size = ( size !== undefined ) ? size : 1;

	var color = ( hex !== undefined ) ? hex : 0xffff00;

	var width = ( linewidth !== undefined ) ? linewidth : 1;

	var geometry = new THREE.Geometry();

	var faces = this.object.geometry.faces;

	for ( var i = 0, l = faces.length; i < l; i ++ ) {

		geometry.vertices.push( new THREE.Vector3(), new THREE.Vector3() );

	}

	THREE.Line.call( this, geometry, new THREE.LineBasicMaterial( { color: color, linewidth: width } ), THREE.LinePieces );

	this.matrixAutoUpdate = false;

	this.normalMatrix = new THREE.Matrix3();

	this.update();

};

THREE.FaceNormalsHelper.prototype = Object.create( THREE.Line.prototype );
THREE.FaceNormalsHelper.prototype.constructor = THREE.FaceNormalsHelper;

THREE.FaceNormalsHelper.prototype.update = function () {

	var vertices = this.geometry.vertices;

	var object = this.object;
	var objectVertices = object.geometry.vertices;
	var objectFaces = object.geometry.faces;
	var objectWorldMatrix = object.matrixWorld;

	object.updateMatrixWorld( true );

	this.normalMatrix.getNormalMatrix( objectWorldMatrix );

	for ( var i = 0, i2 = 0, l = objectFaces.length; i < l; i ++, i2 += 2 ) {

		var face = objectFaces[ i ];

		vertices[ i2 ].copy( objectVertices[ face.a ] )
			.add( objectVertices[ face.b ] )
			.add( objectVertices[ face.c ] )
			.divideScalar( 3 )
			.applyMatrix4( objectWorldMatrix );

		vertices[ i2 + 1 ].copy( face.normal )
			.applyMatrix3( this.normalMatrix )
			.normalize()
			.multiplyScalar( this.size )
			.add( vertices[ i2 ] );

	}

	this.geometry.verticesNeedUpdate = true;

	return this;

};