So I will be DMing a new campaign, and we are going to be starting with the module for The Sunless Citadel. I have a very large .jpeg file for all of the dungeon maps, and plan on using my little projector, mounted above the table, to project the map onto the table to use as the battle mat.

Here is the problem, how would I keep from revealing the entire dungeon level to the players all at once, while still being able show the areas they are in/have already been too?

Initially, I was thinking of using a thick card stock (flash cards) and some tape to block portions of the projected image before it got to the table, but that seems like a lot of additional work every time they enter a new room.

Does anyone here have any experience using digital copies of maps and projectors, or even tables with a built-in screen?

  • 1
    \$\begingroup\$ If you are projecting your screen you could use photoshop/paint/other to create multiple layers to block out individual rooms/areas. As they move through you could hide/show each layer again to reveal/hide areas. \$\endgroup\$
    – mullac
    Commented Nov 15, 2019 at 4:43
  • 1
    \$\begingroup\$ @mullac your comment looks like an answer to me. \$\endgroup\$
    – Dale M
    Commented Nov 15, 2019 at 5:27
  • 1
    \$\begingroup\$ Possibly related: rpg.stackexchange.com/a/51602/43778 \$\endgroup\$
    – Kadin
    Commented Nov 15, 2019 at 5:56
  • \$\begingroup\$ @Kadin Thank you for the related answer link, other answers here have covered basically the same as the linked answer. Much appreciated. \$\endgroup\$ Commented Nov 15, 2019 at 20:14

4 Answers 4


Basic set up

Use the projector as an extension of the screen. Do not copy the main screen! So you have your own workspace (notebook or PC monitor) and the projected view.

Roll20 way

Make 2 account and use one account as a game master and the other as a player in one game, where you uploads all of your map. Than you can use the built in fog of war. You can open two browser one you can pull to the projector's view, and make it full-screen (in Google Chrome with the F11). Be aware that the whole map is shown on the view. The game master stay on your notebook where you can take control.

GIMP way

You can use the GIMP as "not docked" mode. So the toolbars will be free from the picture view. You can simply pull the picture to the projector view, and the windows with the layers can stay on your notebook's view. Be aware that you created all of the layers which hides the map.

  • \$\begingroup\$ Thank you for the detailed explanation for each of the options you provided. I had completely forgotten about Roll20. \$\endgroup\$ Commented Nov 15, 2019 at 20:15


I run a similar setup in my campaigns. For showing my maps, I use maptool by rptools. They have some quite advanced support for managing vision and line of sight.

  • You have the basic options of revealing shapes, such as rectangles or freely drawn regions. This is similar to using paint to block regions.
  • Additionally, it can use line-of-sight to automatically reveal regions based on the position of player tokens. I find that this gives an extra level of immersion to the gameplay and can actually reduce the burden on the GM during playtime. For example, placing a token in front of a window can automatically show some contents of the room, whilst keeping some unseen corners hidden.
  • Support for soft fog: after leaving a room, you will still see the map, but any other tokens in the room will become invisible. I.e. PC's remember what a room looks like, but are no longer aware of the contents. This is ideal for cases where reinforcements have entered a room.
  • It has some extra more advanced features such as light sources, vision blocking by objects/npcs, player-based viewing distances, ...

Personally I only use it for the management of vision, but since it is designed for online play, it has a lot of extra helpful tools and macros, which you might find useful as well.

Due to this reason, it has a somewhat harder learning curve than some of the other options mentioned here, but once you get the hang of it, everything works quite smoothly.

  • 2
    \$\begingroup\$ I've used maptool myself and would call this answer the 'hard' answer, but also the best. A tool like photoshop/gimp is certainly easier but provides less flexibility. Maptool auto calculates sight ranges, move speed and can even place soft fog (can see structure but not monsters) in areas the characters have left. It adds an excellent level of immersion while reducing DM effort in-game. \$\endgroup\$
    – Spartacus
    Commented Nov 15, 2019 at 18:13
  • \$\begingroup\$ I am now trying Lost Mines of Phandelver; bought with the Starter set. You need to get used to MapTool, but after you do, it's a most excellent tool -- automatic sight, distance and fog of war calculations and showing. You add player tokens on separate layer and can move them, and see their LoS and reveal fog. I photographed the maps from the adventure and use them as background of MapTool map. Doing live sessions, and a laptop connected to TV makes you all set for the adventure. \$\endgroup\$
    – Gnudiff
    Commented Feb 11 at 15:16

Using Photoshop/Paint/Other photo editing software

You can use Photoshop (or other photo editing software), set the map as the background, and create multiple layers that cover each area. For example, I would create a black square over each room in a map as an individual layer. From there you can show/hide each layer as they move through each room.

enter image description here enter image description here

This method may not work as well for large open spaces, and the shapes can be slightly tricky to create for unnatural areas like caves. It just depends on how precise you want it to be. One good benefit of this technique is that you can also have monster tokens and other things like hidden doors ready to go. Simply just hide them before projecting the map, then show them if/when they are revealed.

  • 1
    \$\begingroup\$ Layer masks would be ideal for open areas since you can paint the mask where ever you want \$\endgroup\$ Commented Nov 15, 2019 at 8:52
  • 2
    \$\begingroup\$ Depending on the map, you might want to instead cut the rooms into their own layers and add them back in when they're revealed as to not reveal what is left to be revealed, in the example above a play knows right away that there are two rooms either side of the central area as well a show big they are, so if they enter one and the whole blanked area isn't removed they'll know if there is a secret area etc. \$\endgroup\$
    – JDM7
    Commented Nov 15, 2019 at 9:31

Their are many ways to hide your map.

The easiest way in my opinion is to use Roll20, with a gm account and a player account (or just make your player all have an account and play by using Roll20), then put the file on Roll20, and use their system of fog of war.

Another is to use an image editor (e.g. gimp, photoshop), and put some black layers on rooms that you will remove when your players comes (or just one big layer that you edit to make it more dynamic). Then you show it to your player (still in the image editor, because you will edit the image in live).


You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .