Both CS2 and Valorant use fog of war, and so does LoL and Dota 2. It works because they have simple geometry in their maps, mostly straight corridors, 90 degree turns so it has blocking walls in all directions. They still have to start sending player information before they get to the corner to avoid pop in effects, so they'll use the map geometry and then adjust the fog of war mesh.
Open world games or if you have complex geometry like buildings with windows and such it's not really worth the effort to implement its useless in most areas of the map.
Sending all to all clients is the simplest and easiest implementation, all other options are much harder to implement and adds a lot of load on the server, especially if you have more players than 10.
Open world games or if you have complex geometry like buildings with windows and such it's not really worth the effort to implement its useless in most areas of the map.
Sending all to all clients is the simplest and easiest implementation, all other options are much harder to implement and adds a lot of load on the server, especially if you have more players than 10.