text: ml.module('three.core.Vector4')
  .requires('three.Three')
  .defines(function(){
  
  /**
   * @author supereggbert / http://www.paulbrunt.co.uk/
   * @author philogb / http://blog.thejit.org/
   * @author mikael emtinger / http://gomo.se/
   * @author egraether / http://egraether.com/
   * @author WestLangley / http://github.com/WestLangley
   */
  
  THREE.Vector4 = function ( x, y, z, w ) {
  
  	this.x = x || 0;
  	this.y = y || 0;
  	this.z = z || 0;
  	this.w = ( w !== undefined ) ? w : 1;
  
  };
  
  THREE.Vector4.prototype = {
  
  	constructor: THREE.Vector4,
  
  	set: function ( x, y, z, w ) {
  
  		this.x = x;
  		this.y = y;
  		this.z = z;
  		this.w = w;
  
  		return this;
  
  	},
  
  	copy: function ( v ) {
  
  		this.x = v.x;
  		this.y = v.y;
  		this.z = v.z;
  		this.w = ( v.w !== undefined ) ? v.w : 1;
  
  		return this;
  
  	},
  
  	add: function ( a, b ) {
  
  		this.x = a.x + b.x;
  		this.y = a.y + b.y;
  		this.z = a.z + b.z;
  		this.w = a.w + b.w;
  
  		return this;
  
  	},
  
  	addSelf: function ( v ) {
  
  		this.x += v.x;
  		this.y += v.y;
  		this.z += v.z;
  		this.w += v.w;
  
  		return this;
  
  	},
  
  	sub: function ( a, b ) {
  
  		this.x = a.x - b.x;
  		this.y = a.y - b.y;
  		this.z = a.z - b.z;
  		this.w = a.w - b.w;
  
  		return this;
  
  	},
  
  	subSelf: function ( v ) {
  
  		this.x -= v.x;
  		this.y -= v.y;
  		this.z -= v.z;
  		this.w -= v.w;
  
  		return this;
  
  	},
  
  	multiplyScalar: function ( s ) {
  
  		this.x *= s;
  		this.y *= s;
  		this.z *= s;
  		this.w *= s;
  
  		return this;
  
  	},
  
  	divideScalar: function ( s ) {
  
  		if ( s ) {
  
  			this.x /= s;
  			this.y /= s;
  			this.z /= s;
  			this.w /= s;
  
  		} else {
  
  			this.x = 0;
  			this.y = 0;
  			this.z = 0;
  			this.w = 1;
  
  		}
  
  		return this;
  
  	},
  
  
  	negate: function() {
  
  		return this.multiplyScalar( -1 );
  
  	},
  
  	dot: function ( v ) {
  
  		return this.x * v.x + this.y * v.y + this.z * v.z + this.w * v.w;
  
  	},
  
  	lengthSq: function () {
  
  		return this.dot( this );
  
  	},
  
  	length: function () {
  
  		return Math.sqrt( this.lengthSq() );
  
  	},
  
  	lengthManhattan: function () {
  
  		return Math.abs( this.x ) + Math.abs( this.y ) + Math.abs( this.z ) + Math.abs( this.w );
  
  	},
  
  	normalize: function () {
  
  		return this.divideScalar( this.length() );
  
  	},
  
  	setLength: function ( l ) {
  
  		return this.normalize().multiplyScalar( l );
  
  	},
  
  	lerpSelf: function ( v, alpha ) {
  
  		this.x += ( v.x - this.x ) * alpha;
  		this.y += ( v.y - this.y ) * alpha;
  		this.z += ( v.z - this.z ) * alpha;
  		this.w += ( v.w - this.w ) * alpha;
  
  		return this;
  
  	},
  
  	clone: function () {
  
  		return new THREE.Vector4( this.x, this.y, this.z, this.w );
  
  	},
  
  	setAxisAngleFromQuaternion: function ( q ) {
  
  		// http://www.euclideanspace.com/maths/geometry/rotations/conversions/quaternionToAngle/index.htm
  
  		// q is assumed to be normalized
  
  		this.w = 2 * Math.acos( q.w );
  
  		var s = Math.sqrt( 1 - q.w * q.w );
  
  		if ( s < 0.0001 ) {
  
  			 this.x = 1;
  			 this.y = 0;
  			 this.z = 0;
  
  		} else {
  
  			 this.x = q.x / s;
  			 this.y = q.y / s;
  			 this.z = q.z / s;
  
  		}
  
  		return this;
  
  	},
  
  	setAxisAngleFromRotationMatrix: function ( m ) {
  
  		// http://www.euclideanspace.com/maths/geometry/rotations/conversions/matrixToAngle/index.htm
  
  		// assumes the upper 3x3 of m is a pure rotation matrix (i.e, unscaled)
  
  		var angle, x, y, z,		// variables for result
  			epsilon = 0.01,		// margin to allow for rounding errors
  			epsilon2 = 0.1,		// margin to distinguish between 0 and 180 degrees
  
  			te = m.elements,
  
  			m11 = te[0], m12 = te[4], m13 = te[8],
  			m21 = te[1], m22 = te[5], m23 = te[9],
  			m31 = te[2], m32 = te[6], m33 = te[10];
  
  		if ( ( Math.abs( m12 - m21 ) < epsilon )
  		  && ( Math.abs( m13 - m31 ) < epsilon )
  		  && ( Math.abs( m23 - m32 ) < epsilon ) ) {
  
  			// singularity found
  			// first check for identity matrix which must have +1 for all terms
  			// in leading diagonal and zero in other terms
  
  			if ( ( Math.abs( m12 + m21 ) < epsilon2 )
  			  && ( Math.abs( m13 + m31 ) < epsilon2 )
  			  && ( Math.abs( m23 + m32 ) < epsilon2 )
  			  && ( Math.abs( m11 + m22 + m33 - 3 ) < epsilon2 ) ) {
  
  				// this singularity is identity matrix so angle = 0
  
  				this.set( 1, 0, 0, 0 );
  
  				return this; // zero angle, arbitrary axis
  
  			}
  
  			// otherwise this singularity is angle = 180
  
  			angle = Math.PI;
  
  			var xx = ( m11 + 1 ) / 2;
  			var yy = ( m22 + 1 ) / 2;
  			var zz = ( m33 + 1 ) / 2;
  			var xy = ( m12 + m21 ) / 4;
  			var xz = ( m13 + m31 ) / 4;
  			var yz = ( m23 + m32 ) / 4;
  
  			if ( ( xx > yy ) && ( xx > zz ) ) { // m11 is the largest diagonal term
  
  				if ( xx < epsilon ) {
  
  					x = 0;
  					y = 0.707106781;
  					z = 0.707106781;
  
  				} else {
  
  					x = Math.sqrt( xx );
  					y = xy / x;
  					z = xz / x;
  
  				}
  
  			} else if ( yy > zz ) { // m22 is the largest diagonal term
  
  				if ( yy < epsilon ) {
  
  					x = 0.707106781;
  					y = 0;
  					z = 0.707106781;
  
  				} else {
  
  					y = Math.sqrt( yy );
  					x = xy / y;
  					z = yz / y;
  
  				}
  
  			} else { // m33 is the largest diagonal term so base result on this
  
  				if ( zz < epsilon ) {
  
  					x = 0.707106781;
  					y = 0.707106781;
  					z = 0;
  
  				} else {
  
  					z = Math.sqrt( zz );
  					x = xz / z;
  					y = yz / z;
  
  				}
  
  			}
  
  			this.set( x, y, z, angle );
  
  			return this; // return 180 deg rotation
  
  		}
  
  		// as we have reached here there are no singularities so we can handle normally
  
  		var s = Math.sqrt( ( m32 - m23 ) * ( m32 - m23 )
  						 + ( m13 - m31 ) * ( m13 - m31 )
  						 + ( m21 - m12 ) * ( m21 - m12 ) ); // used to normalize
  
  		if ( Math.abs( s ) < 0.001 ) s = 1; 
  
  		// prevent divide by zero, should not happen if matrix is orthogonal and should be
  		// caught by singularity test above, but I've left it in just in case
  
  		this.x = ( m32 - m23 ) / s;
  		this.y = ( m13 - m31 ) / s;
  		this.z = ( m21 - m12 ) / s;
  		this.w = Math.acos( ( m11 + m22 + m33 - 1 ) / 2 );
  
  		return this;
  
  	}
  
  };
  
  
  });