help to to make pixlate shader on babylon.js

I am trying to come up the pixelated shader effect as seen on three.js 

the three.js version 

http://oos.moxiecode.com/js_webgl/c64_shader/

the three.js version shader code

https://github.com/chribbe/ThreeJS-GameboyStyleShader/blob/master/js/PixelateShader.js

and this is what I came up by using three.js , a pixlated 3d christmas scene. (I would really like to make similar one on babylon.js)

http://amoyeh.co/threejs/christmas2015/index.html

since I only understand a bit about shader, any help is appreciated

this is the version I came up so far.

http://www.babylonjs.com/cyos/acpr/#1HRCVZ

Thanks a lot~