Properly orient helper in direction of light target

Author: WestLangley

src/helpers/DirectionalLightHelper.js

@@ -73,7 +73,7 @@ DirectionalLightHelper.prototype.update = function () {
 		v2.setFromMatrixPosition( this.light.target.matrixWorld );
 		v3.subVectors( v2, v1 );
 
-		this.lightPlane.lookAt( v3 );
+		this.lightPlane.lookAt( v2 );
 
 		if ( this.color !== undefined ) {
 
@@ -87,7 +87,7 @@ DirectionalLightHelper.prototype.update = function () {
 
 		}
 
-		this.targetLine.lookAt( v3 );
+		this.targetLine.lookAt( v2 );
 		this.targetLine.scale.z = v3.length();
 
 	};