I believe, i saw a post related to this(Volumetric Cloud) topic.So, i posted it anyway.It might come out handy. - Esenthel

http://software.intel.com/en-us/articles...platforms/

They are already implemented in the Esenthel engine.
Perhaps he can use it to optimize a bit, I wouldn't know.
Chances are he has seen it already ^^

I wonder why people don't use volumetric billboards for these kinds of things. You just need a couple of them and a good particle distribution system to make it seem random/natural and pleasant.

I mean, if it's good for trees it should be good for clouds.
http://www.antisphere.com/Research/Volum...boards.php