Fog of War

Hiding information about parts of game worlds that are not being observed or have not yet been explored by players.

While many games give players views of game worlds that could not be achieved by any diegetic entity, it in many cases makes sense to limit players information to that which his or her units could perceive. This juxtaposition between a non-diegetic player's view and the perception possible by diegetic entities is called Fog of War, from the awareness from military leaders that they have to act without full information about the situation.

Examples

Fog of War originated in Wargames and is here typically limited to the presence of identity of enemy units. Examples of such games include Advanced Squad Leader, Rommel in the Desert, and Stratego. A futuristic example is Space Hulk.

Computer-based Strategy Games can introduce a second level, hiding the game world until explored, since computers can easily handle the added excise. Games that make use of this include the Advance Wars, Age of Empire, Civilization, Europa Universalis, and the Hearts of Iron series but it should be noted that Drakborgen and Zombies!!! shows that Board Games can also support this type of Fog of War. For the Civilization series, players start with just the areas around his or her starting units explored and the choice between whether to put resources into improving ones cities or exploring the environment can make the difference between success or failure in the game. In later installments of the game, some units can be given upgrades that improve their range and thereby lessen the Fog of War.

Metroid Fusion reveals most of the layout of each level and even explicitly indicates the places the player has already visited. The game further indicates the location of the power-ups on the overview map, but not the exact location on the play area. The in-game tactical maps in the Battlefield series show all terrain features, friendly units, and all enemy units spotted by any friendly units.

The GiantBomb web site has a page for Fog of War listing numerous examples.

Using the pattern

Two main design choices exist for Fog of War: is the Fog of War shared by all players and does the Fog of War return after players have explored an area? The second design choice can be modulated further by differentiating between a Fog of War that hides the Game World and a Fog of War that does not hide the Game World but does hide game elements in it.

Fog of War relies on the movement and observation ranges of Avatars or Units to explore unknown areas. This provides the game designer with opportunities to provide different levels of proficiency for different Units, giving them Privileged Abilities or Asymmetric Abilities and creating Orthogonal Unit Differentiation. For example, in the real-time strategy game WarCraft II players can choose to build very strong attack units which have limited capabilities for gaining information about the enemy units they encounter. This is an example of applying the Trade-Offs pattern between making Gain Information or Eliminate goals easier, although the actual balance is not easy to judge. One way of creating Fog of War is to use Tile-Laying and having the Tiles upside down until they have been explored. However, this makes the Fog of War common to all players.

Games with Game State Overview typically apply the use of Fog of War at the same level as for the game world. The most common exception can be found in games using Third-Person View. Such games may let players have full view of the area currently visited, in essence having no Fog of War in the Game World view but having one in the Game State Overview which is updated as different parts of the Game World are explored.

- can inst.

Some type of Fog of War is a requirement for a game if the game is to have Secret Resources or Asymmetric Information.

Can Modulate

Game Worlds, Mini-maps,

Can Be Instantiated By

Avatars, Units, Line of Sight, Tile-Laying

Can Be Modulated By

Privileged Abilities

Interface Aspects

Fog of War is an Information Pattern.

Consequences

Fog of War modulates players' perception of Game Worlds. It provides means of giving Imperfect Information in games with Third-Person or God Views comparable to that which comes automatically in games with First-Person Views. It can modulate God Fingers so that one has the freedom to fully move over entire Game Worlds but without revealing all information within them. In games with Reconfigurable Game Worlds, Fog of War can require players to engage in Memorizing.

Since knowing the terrain of Game Worlds and what it contains most often gives tactical advantages, the presence of Fog of War naturally creates Gain Information and, more specifically, Game World Exploration goals. When Fog of War comes in two layers, making a difference between what has not been seen at all and that which currently is not seen, the pattern also modulates Game World Exploration since it encourages players to repeatedly explore the same areas to notice difference. When this becomes a more structure gameplay activity, it is in fact a Guard or Reconnaissance goal. Needing to consider Fog of War in these ways affect how players can and need to do Stimulated and Tactical Planning.

Fog of War can modulate many types of actions through introducing Imperfect Information, but this is probably most directly noticeable in games with Combat.

Relations

Can Instantiate

Gain Information, Game World Exploration, Guard, Imperfect Information, Reconnaissance

with Reconfigurable Game Worlds

Memorizing

Can Modulate

Combat, Game World Exploration, Game Worlds, God Fingers, God Views, Mini-maps, Stimulated Planning, Tactical Planning, Third-Person Views

Can Be Instantiated By

Avatars, Line of Sight, Tile-Laying

Can Be Modulated By

Privileged Abilities

Possible Closure Effects

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Potentially Conflicting With

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History

An updated version of the pattern Fog of War that was part of the original collection in the book Patterns in Game Design.