Renders [page:ArrowHelper arrows] to visualize an object's [page:Face3 face] normals.
			Requires  that face normals have been specified on all 	[page:Face3 faces] or calculated
			with [page:Geometry.computeFaceNormals computeFaceNormals]. 
			Note that this only works with the objects whose geometry is an instance of [page:Geometry].
			For [page:BufferGeometry] use a [page:VertexNormalsHelper] instead.
		
		geometry = new THREE.BoxGeometry( 10, 10, 10, 2, 2, 2 );
		material = new THREE.MeshBasicMaterial( { color: 0xff0000 } );
		box = new THREE.Mesh( geometry, material );
		helper = new THREE.FaceNormalsHelper( box, 2, 0x00ff00, 1 );
		scene.add( box );
		scene.add( helper );
		
		
		[page:Object3D object] -- object for which to render face normals.
		[page:Number size] -- (optional) length of the arrows. Default is *1*.
		[page:Hex color] -- (optional) hex color of the arrows. Default is *0xffff00*.
		[page:Number linewidth] -- (optional) width of the arrow lines.  Default is *1*.
		
See the base [page:LineSegments] class for common properties.
See [page:Object3D.matrixAutoUpdate]. Set to *false* here as the helper is using the objects's [page:Object3D.matrixWorld matrixWorld].
The object for which the face normals are being visualized.
Length of the arrows. Default is *1*.
See the base [page:LineSegments] class for common methods.
Updates the face normal preview based on movement of the object.
[link:https://github.com/mrdoob/three.js/blob/master/src/[path].js src/[path].js]