[RMXP] Creating 'Fog of War' for a world map?

Hi,

I have a world map that the player is transferred to when they select it from their menu and then when they hit escape they are transferred back to the exact location they were before.  So it's a proper 'map' as far as the game is concerned, it's not just a picture or anything.

What I need to do though is put fog/clouds over the parts of the map the player has not been yet.  I can't think of a good way to do this, does anybody have any experience with this?

I believe wachunga made a fog of war script for RMXP. Try googling "wachunga fog of war"