Fog of war in video games limits what a player knows about the world, especially enemy positions outside their unitsâ vision. In a strategy game it often appears as unexplored black terrain or a dimmed area you remember but cannot currently observe. The broader idea of making decisions with incomplete information is much older than computers, and games use it in many different ways.
The reason it has survived is simple. Limited information makes decisions interesting. When you cannot see the whole board, you have to guess, scout, commit, regret, adapt. That loop is the engine of strategy, horror, exploration, and multiplayer tension. This guide walks through where fog of war came from, the different flavors designers actually ship, a simple model of how it works under the hood, and why the technique keeps mutating to fit new genres.
Table of Contents
- Origins: Kriegsspiel and the Prussian Wargame
- The Three Types of Fog of War
- RTS Fog of War: Dune II, Warcraft, StarCraft
- How Fog of War Works Under the Hood
- Fog of War in Horror and Exploration
- Fog of War in Modern Multiplayer
- Why Designers Keep Coming Back to It
- FAQ
Origins: Kriegsspiel and the Prussian Wargame
Military writers used uncertainty as a central problem long before video games. Clausewitz discussed it in On War, but attributing the exact phrase âfog of warâ to him oversimplifies the history. Historian Eugenia Kiesling examines that distinction in her essay on fog and friction. The useful connection here is the commander who must act without a complete, reliable picture.
Nineteenth-century Prussian Kriegsspiel brought limited information into military training games. The International Kriegsspiel Society preserves several rules traditions, including Reisswitzâs 1824 system. Umpires could manage what opposing players learned about movements and encounters. The details varied between versions, but the design problem is familiar: the referee knows more than either commander.
Tabletop wargames continued exploring hidden movement, separate maps, and delayed information. Computers made it possible to manage such restrictions without a human referee constantly deciding what to reveal. It is a useful family resemblance, without assuming every later game directly copied one Prussian rulebook.
The Three Types of Fog of War
Three related ideas help explain the design. The first two describe map information; the third describes how a game can decide what is visible.
Unexplored Black
An unexplored area may start black, hiding terrain and anything on it until a unit scouts it. Dune II used progressive map revelation in 1992. Its exploration shroud is different from the returning fog associated with later RTS games: revealing a place and keeping it under observation are two separate design choices.
Explored But Dimmed (True Fog)
Once explored, terrain can remain known while enemy movements become hidden again when friendly vision leaves. Blizzardâs Warcraft II guide explains this distinction between unexplored blackness, a dimmed explored region, and the currently visible area around friendly units or buildings. Roads stay where they are; the enemy army does not.
Line of Sight and Sensor Cones
Line of sight concerns what a unit can observe right now. Range, walls, terrain, and sometimes facing direction can affect it. A guardâs sight cone in a stealth game is a detection rule; an RTS can combine visibility with a remembered map. Both restrict information, but a wall blocking your view is not automatically the same system as a strategy gameâs map fog.
RTS Fog of War: Dune II, Warcraft, StarCraft
Real-time strategy made the difference between exploration and observation especially important. Dune II and the original Warcraft used exploration shrouds; Warcraft II added the familiar returning fog over previously explored ground. StarCraft carried information management into another influential competitive setting. These were different implementations, not one finished system passed unchanged between games.
In StarCraft, scouting can feel like a tax you pay throughout the match. Seeing an opponentâs buildings or army composition gives you a chance to respond before the surprise reaches your base. In Brood War, dealing with burrowed Lurkers also involves detection: ordinary vision and the ability to reveal a concealed unit are not identical. The map can feel like a chessboard where half the pieces have quietly gone for a walk.
Scouting decisions also interact with terrain, detection abilities, and changing maps. In games with procedurally generated maps, progressive reveal can make learning the layout part of play. A designer may instead reveal the geography immediately and hide only enemy activity. Randomness and visibility are separate tools that can work together.
How Fog of War Works Under the Hood
A simple way to model strategy-game fog is a grid of visibility states for each player or team. Each cell can be unknown, explored but not currently observed, or currently visible. This is an explanatory model, not a requirement that every engine uses the same grid, update frequency, or rendering method.
During a visibility update, units and other vision sources reveal nearby areas according to the gameâs rules. When a source moves away, those areas can lose current visibility while keeping their explored status. Several sources may overlap, so removing one scout should not hide ground still watched by another.
The display can then use darkness or shading to communicate those states. Moving enemies usually disappear when no longer observable; a game may preserve a last-seen building or marker as stale information. Remembering that something was there is different from receiving live updates about it.
For a concrete implementation, Riotâs 2017 League of Legends graphics breakdown describes a CPU-maintained 128-by-128 fog grid converted into a larger, blurred texture to shade the scene and minimap. That is one way to draw the result. Deciding what a player knows, deciding what geometry to render, and deciding what data to send over a network remain separate questions.
That separation matters for cheats. Riotâs 2020 explanation of VALORANTâs Fog of War describes withholding irrelevant enemy positions from clients to reduce wallhack opportunities. Its visibility checks are deliberately generous enough to avoid enemies suddenly popping into view. Hiding data can help, but it is not an exact promise to send nothing outside a playerâs current pixels. Nor does every competitive game use this architecture: some clients receive information they are instructed not to display.
Fog of War in Horror and Exploration
Horror games exploit a related feeling: you know something could be nearby but cannot get a clear look. Literal mist, darkness, and restricted camera angles can all create it. These atmospheric techniques are cousins of strategic fog of war, rather than proof that every horror game maintains an RTS-style hidden-information map.
Call it uncertainty as dread. A fixed camera can withhold the view around a corner; a narrow beam can make the next room feel enormous. The player still controls the character, but the picture needed to feel comfortable is missing. Comfort was apparently not in the level designerâs budget.
Exploration games also make discovery valuable. The tile-by-tile visibility found in many classic roguelikes can preserve explored geography while concealing activity outside the characterâs view. A missing map, a limited view, and an undiscovered story clue create different kinds of uncertainty; they need not share an implementation.
The claustrophobic horror game Iron Lung makes restricted perception the experience. Its developerâs description specifies an incomplete map, proximity sensors, and an external still camera for navigation. You are not simply looking through a window or drawing a complete picture from sonar. Each grainy photograph gives you information you may regret requesting.
Fog of War in Modern Multiplayer
Battle royale games likewise ask you to act without knowing where everyone is. Sight, sound, and communication supply clues. A shrinking playable area pressures people to move and can produce encounters, but it is a separate mechanic from fog of war: changing the safe zone does not itself reveal every opponent.
MOBAs such as League of Legends and Dota 2 make team vision and ward placement strategic resources. A ward can tell you whether a route is being used, while an unwatched route leaves room for an unpleasant guess. The details of acquiring and using wards differ between games; the central decision is where information is worth spending resources to obtain.
Asymmetric horror games can give the two sides different clues. In Dead by Daylight, the terror-radius heartbeat warns Survivors about a nearby Killer, rather than serving as the Killerâs universal survivor detector. Behaviourâs March 2023 developer update explains the visual version of that warning. This is information asymmetry, not a rule making the Killer invisible beyond a fixed radius.
Why Designers Keep Coming Back to It
Fog of war invites the imagination to fill gaps. A black tile could contain a useful resource, an ambush, or absolutely nothing. After one disastrous scouting trip, absolutely nothing can start looking suspicious. The unknown becomes part of the drama without needing an elaborate cutscene.
It also changes the decisions available. Chess shows both players the position and remains enormously difficult. Add hidden positions and you introduce uncertainty about what is on the board, alongside the challenge of choosing good moves. Scouting, bluffing, and judging risk can then matter in ways they do not in ordinary chess. Full information never meant automatic or easy victory.
The broad idea travels well, although the mechanics differ. An umpire hiding orders, an RTS concealing enemy units, and a horror game restricting the camera can all make uncertainty interesting. Even Metroidvania map systems can make the choice of where to explore meaningful. Naming the particular kind of missing information helps explain why each design works.
FAQ
What is fog of war in video games?
Fog of war restricts information about the game world, commonly hiding enemy activity outside friendly vision. Strategy games often distinguish unexplored terrain from known ground that is not currently observed.
What was the first video game with fog of war?
There is no need to award one universal first place: hiding terrain, concealing opponents, and limiting sight are different features with different histories. Tabletop precedents long predate computers, and early RTS exploration shrouds differ from the returning fog seen in Warcraft II.
Why do RTS games use fog of war?
It makes scouting and information management valuable. You may need to spend time or resources learning what an opponent is doing, and you can try to conceal your own plans. Games with full information can still be strategically rich; fog changes the kind of decisions they offer.
Is fog of war just a graphical effect?
No. The overlay communicates a visibility rule. A networked game may additionally withhold hidden data from clients, which can reduce cheating opportunities, but that is a separate implementation choice rather than a property of every fog effect.
What is the difference between fog of war and line of sight?
Line of sight describes what can be observed from a position. Fog of war can combine observation with exploration history, team vision, and rules about what remains known afterward. Their relationship depends on the game.
Conclusion
Fog of war turns missing information into something worth playing with. It can make a scout valuable, an empty corridor tense, and a familiar map surprising. It does not need one universal algorithm or a claim to explain every multiplayer game. Sometimes all a designer needs is a hill you cannot see behind. Naturally, that is where the trouble lives.
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