Here I am not talking about how to render fog of war, but how to model exploring of terrain in a more sophisticated way.
In a straight-forward approach, terrain explored by a game unit is simply represented by a circle whose radius is how far this unit can see. And visible area is just union of isometric circles. But I can tell that it is not the case in popular games.
Please take a look at the following screenshot from League of Legends, for example.
The sight of view is anisotropic. The shape of surrounding terrain is also taken in to account.
Any idea how this can be done?