mrdoob/three.js — pull request #3438 by WestLangley (2013-05-06 19:35:50+00:00)
Title: Improved VertexNormalsHelper and FaceNormalsHelper

In order to get the math right, I found it necessary to require a `helper.update()` function inside the `render` loop.

I was able to maintain the lightweight geometry, however.

fiddle: http://jsfiddle.net/7QPJU/1/

Feel free to cherry-pick.