Using billboard guis, you can make volumetric lighting, a while back it used to be a big topic but has died down since then, due to one big problem. The back face of the billboard gui is always shaded and makes the effect look ugly and straight up not work.
Heres an example of an attempt I did quite recently.
I thought it was unsolvable until I came across THIS video which blew my mind on how he did it.
Can anyone please help me find out how he did this, because 1 it fascinates me and 2 I have many optimization plans that could possibly make be for so much more than just showcase games.
NOTE: the video I linked is about 4 years old so who knows if the effect was patched in later updates but if anyone can tell me anything about that please let me know.