[page:Line] →

# [name]

Renders [page:ArrowHelper arrows] to visualize an object's [page:Face3 face] normals. Requires that the object's geometry be an instance of [page:Geometry] (does not work with [page:BufferGeometry]), and that face normals have been specified on all [page:Face3 faces] or calculated with [page:Geometry.computeFaceNormals computeFaceNormals].

## Example

`geometry = new THREE.BoxGeometry( 10, 10, 10, 2, 2, 2 ); material = new THREE.MeshBasicMaterial( { color: 0xff0000 } ); object = new THREE.Mesh( geometry, material ); edges = new THREE.FaceNormalsHelper( object, 2, 0x00ff00, 1 ); scene.add( object ); scene.add( edges );` [example:webgl_helpers Example using various helpers]

## Constructor

### [name]( [page:Object3D object], [page:Number size], [page:Color color], [page:Number linewidth] )

object -- object for which to render face normals
size -- size (length) of the arrows
color -- color of the arrows
linewidth -- width of the arrow lines

## Properties

### [property:Object3D object]

The attached object

## Methods

### [method:null update]()

Updates the face normal preview based on movement of the object.

## Source

[link:https://github.com/mrdoob/three.js/blob/master/src/[path].js src/[path].js]