If you want to use this effect on your site, please feel free but PLEASE DO NOT HOTLINK TO MY FILES! Copy the files on github to your own server!
I adapted one of the Mr.doob‘s three.js Particle examples. I’ve extended the particle class and added velocity to update it’s position. Anyone that knows me knows that I’ve been making snow for a while now! Most people’s first approach is to make the snow move left and right but actually you don’t need to do that. If there are lots of flakes all moving in different directions it pretty much has the same effect, and it gives much simpler and more uniform effect.
As ever, the code is fully commented and available on github.
[UPDATE: code has been updated now to work in Three.js revision 46]