[LVL ED] Window Lightrays

[KiraImmortal]

Particles, general lighting and bilboard making things are easy for me now, but in my upcoming custom story for my latest mod, i would like to do realistic lighting for the windows (with good-looking light rays coming from outside). i can create quite good ones, but not all of them looks so realistic, and i can't imagine how can i make them better :/ is there a tutorial for this on this forum, or can anyone give me a quick training in using these effects perfectly?