Multiple mobs can contribute to a client's sight so this is all set to include in an RTS game.
To use the library, here's all you have to do:
// initialize fog of war for the client
client.fog = new(client)
client.fog.init()
// define the mob's sight range and tell the library that this
// mob's sight contributes towards its client's visibility
fog_sight = new(src, client, 2)