Hi! its way to make a GLSL filter like in other “AAA” games, called “god rays” or volumetic lights? i know, here in forum someone make a resource with mountains and this filter, but this not working propetly in 2.5+ … its that hard make something like this? can anybody do this? 
Search for ‘HDR 2.0’ on those forums,there you can find light scattering.
But atm its very resource expensive and not quite usable.