@sugar_in_your_tea Your response about wall-hacks is my "don't tell the game anything" comment. It's really really damn slow. You typically don't want to do frame-by-frame determination of if an opponent is just in view or not (because that's a full render), so you send the info to the client once it's possible... at which point the client knows.
Even if the game isn't hacked, the video pipeline "knows", and hacks have moved to be outside of the game space (thus the move to kernel-based)