Merge remote-tracking branch 'Wilt/patch-2' into dev

src/core/Vector3.js

@@ -249,6 +249,10 @@ THREE.Vector3.prototype = {
 
 	},
 
+	angleTo: function ( v ) {
+		return Math.acos( this.dot( v ) / this.length() / v.length() );
+	};
+
 	distanceTo: function ( v ) {
 
 		return Math.sqrt( this.distanceToSquared( v ) );