[mattdesl]

I quite like the look of the blue noise dithering on this. Are you using just a texture as a mask, or something else?

[rikroots]

It's an array of pre-calculated values that I extracted from an image donated to the Public Domain by Christoph Peters (the link is an interesting read about bluenoise - recommend!) - http://momentsingraphics.de/BlueNoise.html

No textures or masks, just brute computing on the CPU.