How to Reveal Unexplored Dungeon Map Areas Without Showing the Whole Map

For an in-person game, put the full map under a sheet of paper, use removable covers, or assemble the map from room-sized tiles as the party moves. These methods are easy to run, though you need a way to prevent players from seeing through or around the cover. A screen or projector can make the map clearer, but still requires a separate way to mask unexplored areas.

For a virtual tabletop, use its manual fog or hide/reveal tools when you want to control exactly what appears. These tools let you uncover map sections by hand. A dynamic-lighting system instead uses token vision, light and wall boundaries to determine what characters can see; it can be useful when visibility changes frequently, but needs accurate wall and light setup. Foundry describes fog exploration as interacting with walls and lighting to determine visibility; Roll20 documents a separate Hide / Reveal Mask tool in its dynamic-lighting help center. Foundry Virtual Tabletop: Lighting, Roll20 Help Center: Dynamic Lighting

For a first run, prefer manual fog if your main goal is dramatic, controlled reveals rather than tracking every line of sight. Pick automatic lighting if your group regularly needs visibility to update as characters move, and you are prepared to configure the scene. Avoid switching approaches mid-session unless you have already tested how they interact.

1. Place the map at the scale and orientation you will use in play. If it has a grid, align it with the tabletop grid before covering it; misalignment can make token movement and reveal boundaries confusing.

2. Cover the entire playable area, including side rooms, secret chambers and corridors beyond the starting area. On a digital map, look for gaps at the edges and between separate fog strokes. On a physical map, check that no portion can be seen from the players’ seats.

3. Decide what the cover represents. A fully hidden map suits an unknown location. If the characters have a rough plan, show that plan separately, perhaps as a player-drawn sketch, rather than revealing the detailed map underneath. Keep GM notes, encounter markers and secret labels off the player-visible layer.

4. Test the player view. If the tool offers a preview, use it; otherwise check the display from a player account or seat. RPG Sessions’ documentation recommends covering the whole playable area before play and checking its Player Preview. The same principle applies to any platform: a GM’s view may show the underlying map through the fog. RPG Sessions: Fog of War

When characters reach a closed door, reveal up to the door and stop. Once it opens, uncover what they can see through the opening, then expand the reveal as they enter or change position. For an ordinary room with no visibility barriers, uncovering the room at once is usually quicker than tracing every square. For a twisting passage, a partly open door or a room divided by pillars, reveal a narrower shape that follows the actual sightline.

A practical rhythm is: pause movement at a threshold, describe what is visible, reveal that area, then let the players decide what to do. This keeps map handling from racing ahead of the fiction. It also gives you a chance to withhold a hidden compartment or an area concealed by a turn in the corridor, without hiding parts the characters have already seen.

Use a coarse reveal for open spaces and a fine one around doorways, corners and unusual boundaries. RPG Sessions documents this large-brush-then-small-brush approach for covering areas; the same brush-size logic helps when revealing them. Some tools let you reveal a polygon or snap a selection to the grid; use those where they make the map easier to read, but don’t spend time outlining every wall if a simple room-shaped reveal is clear. RPG Sessions: Fog of War

A revealed patch can mean “the party has been here” or “the party can see this now.” Those are different rules. With manual fog, decide whether previously uncovered rooms stay visible when the party leaves. If they do, the shared map becomes an exploration record. If not, cover the space again when it falls out of sight. Tell players which convention you use before the first reveal, especially if they use the visible map to navigate.

Automatic vision tools may track explored areas separately from current light and line of sight. Foundry’s lighting controls, for example, include recorded fog-of-war exploration that can be reset; its visibility also depends on configured walls and lighting. That means a setup error can expose too much or leave areas unexpectedly hidden. If you use automatic vision, check wall placement, token vision and light sources on a test scene before relying on it in a session. Foundry Virtual Tabletop: Lighting

Before play, inspect the player view for three common leaks: a map edge left uncovered, a reveal brush that crossed a wall, and text or tokens placed on a visible layer outside the fog. If your platform lets you select or interact with covered assets, check that too; some tools mask background art and tokens together, while others may treat layers differently.

During play, correct a stray reveal as soon as you notice it. Manual fog tools commonly provide a way to cover an area again, though the exact controls vary by platform. Roll20’s legacy wiki describes static fog as manually revealed or hidden, and the current help center lists Hide / Reveal Mask among its tools. Test the relevant controls in your own version rather than relying on old shortcuts or labels. Roll20 Help Center: Dynamic Lighting, Roll20 Wiki: Fog of War

If a player glimpses a hidden room by mistake, you can cover it again, but the table may already have seen it. A more reliable safeguard is to put secret annotations and encounter information on the GM-only layer, not merely behind fog. Treat fog as a visibility aid, not the sole protection for information you need to keep private.

Use whole-room reveals when speed and a clear shared picture matter most. Reveal corridors in segments when turns, doors or branches affect what the party can see. Use automatic lighting when character position and light sources matter often enough to justify careful setup. For a physical map, lift or place covers at thresholds and keep extra paper or tiles ready for irregular shapes.

The best method is the one you can operate consistently while running the adventure. Cover the full map, confirm the player view, agree whether revealed areas remain visible, and uncover only what the characters can currently perceive or have already explored. That routine keeps the map useful for navigation while leaving unexplored rooms unseen.

• Foundry Virtual Tabletop, “Lighting” — https://foundryvtt.com/article/lighting/

• Roll20 Help Center, “Dynamic Lighting” — https://help.roll20.net/hc/en-us/categories/360003712734-Dynamic-Lighting

• RPG Sessions, “Fog of War” — https://rpgsessions.com/docs/maps/features/fog-of-war

• Roll20 Wiki, “Fog of War” — https://wiki.roll20.net/Fog_of_War