A pared-down version of this:
https://technology.riotgames.com/news/demolishing-wallhacks-valorants-fog-war
Blue is controlled by the user.
Their client is connected to an omniscient server (hosted by myself!), which feeds back the position of
Red ONLY if Red is at least adjacent
to Blue's "fog of war" (area obscured by terrain). This fog of war visibility
map is pre-compiled, where each square algorithmically determines the other squares it should be able to see.
Rudimentary wallhacks are provided to demonstrate side-stepping
Blue-client's knowledge of Red. Whenever the hacked-client
has Red's position, it will attempt to display it,
regardless of the fog of war. However, because the server only sends Red's
position when Red is on a
Blue-visible square, the damage of the wallhacks is limited to slightly beyond the fog of war.
Repo here