This small set of scripts are ideal for anyone making grid-based games that wants a light and easy to use fog of war system. The basis for the scripts are tiles, which are layered over the room then cleared away around a given point when required. You can add multiple instances which clear the fog to the room.
As a bonus, the scripts also permit a VERY basic grid-based lighting system, which only permits one light source, but that source will convincingly illuminate a given area, and cast tile "shadows" behind any blocker instances.
Please note that the scripts use a rounding method to convert room coordinates to grid coordinates, meaning that you may have to offset the origin (x,y) by about half the tile size +1 when calling the update script. So for a 16x16 tile size, the arguments would be (x + 9, y + 9). The actual values you use will depend greatly on the tile size you have and the origin of the instance calling the script.
UPDATE: There is now a new script included with this to calculate the correct grid squares between two points. This is called "Bresenham's Line Algorithm" and is VERY handy in a number of situations. It is a stand-alone script so that you can use it in other games or situations.