function gauss( x, sigma ) {

			return Math.exp( - ( x * x ) / ( 2.0 * sigma * sigma ) );

		}
@author alteredq / http://alteredqualia.com/
@author zz85 / http://www.lab4games.net/zz85/blog
@author davidedc / http://www.sketchpatch.net/

ShaderExtras currently contains:

	screen
	convolution
	film
	bokeh
 sepia
	dotscreen
	vignette
 bleachbypass
	basic
 dofmipmap
 focus
 triangleBlur
 horizontalBlur + verticalBlur
 horizontalTiltShift + verticalTiltShift
 blend
 fxaa
 luminosity
 colorCorrection
 normalmap
 ssao
 colorify
 unpackDepthRGBA