function resetPosition () {

		scope.position.set( scope.position.x, scope.position.y );

	}
@author arya-s / https://github.com/arya-s

This is a helper for visualising a given light's shadow map.
It works for shadow casting lights: THREE.DirectionalLight and THREE.SpotLight.
It renders out the shadow map and displays it on a HUD.

Example usage:
	1) Include <script src='examples/js/utils/ShadowMapViewer.js'><script> in your html file

	2) Create a shadow casting light and name it optionally:
		var light = new THREE.DirectionalLight( 0xffffff, 1 );
		light.castShadow = true;
		light.name = 'Sun';

	3) Create a shadow map viewer for that light and set its size and position optionally:
		var shadowMapViewer = new THREE.ShadowMapViewer( light );
		shadowMapViewer.size.set( 128, 128 );	//width, height  default: 256, 256
		shadowMapViewer.position.set( 10, 10 );	//x, y in pixel	 default: 0, 0 (top left corner)

	4) Render the shadow map viewer in your render loop:
		shadowMapViewer.render( renderer );

	5) Optionally: Update the shadow map viewer on window resize:
		shadowMapViewer.updateForWindowResize();

	6) If you set the position or size members directly, you need to call shadowMapViewer.update();