Kartofel, that looks very nice! BTW it reminded me of the shader pipeline that was made by txesmi, take a look at this video: Ligths in the fog
cool stuff! Pretty sure he's using the same (or a very similar) method as me. But he most likely did some good optimizations.
In my case it's kind of a bruteforce approach... the lightrays in the screenshot I've posted increase the sample count from 6-9 (light + shadow) to 206 (light + shadow + lightrays) samples per pixel ...per light ;_;
That's why a single light at a 1600x900 resolution causes the framerate to crash down to 50-60 fps. On second thought, however, it should be waaay faster with some clever optimazations like using a lower resolution for the lightrays and adding dithering (greatly decreasing the sample count at the expense of some visual noise)