Fog of War in material only?

I have bought a fog of war asset on the marketplace.
The problem is, that any wall needs to be an actor_bp…

So i thought about, to create a material which does all the things for the fog of war.
But i have no idea how…

It should allow to only show areas where the top-down-character can look at, if there´s a wall in it´s way, the player can´t see behind the wall.

What do you think, is this possible?

And how would you do that?