This is a high-tech solution for the traditionally low-tech table top gaming—whose death knell has been sounded again and again, falsely, since the rise of computer RPGs in the '90s. For projector based D&D, the Dungeon Master scans in adventure maps and separate what the players should see and what the DM should see onto different layers in Photoshop before the game starts. The Photoshop image is then displayed on a table through a suspended digital projector during the game, allowing the game tokens to be placed directly onto the map.
When certain events happen, such as players advancing in the map or meeting an event, the DM erases part of the mask or reveals a new layer to show the appropriate map info—very cool. The downside is of course, the equipment cost and the time to set up all the maps and photoshop the appropriate portions.
Great idea nonetheless, that makes table top gaming a little bit more automated. A tip of the wizard hat to you, Jans.
Digital Map Projection [The Hypertext d20 SRD]