Line of sight, sometimes written line-of-sight or abbreviated to LoS, is the visibility (that is, who can see what) on the playing field in wargames and some

role-playing game A role-playing game (sometimes spelled roleplaying game, or abbreviated as RPG) is a game in which players assume the roles of player character, characters in a fictional Setting (narrative), setting. Players take responsibility for acting out ...

s (RPGs). Many abilities can only be used on entities within a character's line of sight. In some games, miniature figures are used to determine line of sight. Many wargames use counters to represent units and determine line of sight. A common technique is to hold a length of thread between two counters. If the thread, held straight, doesn't encounter any obstacles, the line of sight is valid. The first computer game to implement line of sight graphics was '' Dungeon'', which was played on a

PDP-10 Digital Equipment Corporation (DEC)'s PDP-10, later marketed as the DECsystem-10, is a mainframe computer family manufactured beginning in 1966 and discontinued in 1983. 1970s models and beyond were marketed under the DECsystem-10 name, especi ...

mainframe computer A mainframe computer, informally called a mainframe or big iron, is a computer used primarily by large organizations for critical applications like bulk data processing for tasks such as censuses, industry and consumer statistics, enterprise ...

(1975).

Examples

tank A tank is an armoured fighting vehicle intended as a primary offensive weapon in front-line ground combat. Tank designs are a balance of heavy firepower, strong armour, and battlefield mobility provided by tracks and a powerful engine; ...

behind a tall hill would not be able to see an enemy tank on the other side of the hill. Therefore, the first tank does not have a line of sight to the enemy tank. Conversely, a squad of soldiers atop the hill may be able to see both tanks, though the tanks may not be able to see them (since the tank's upward line of sight is limited). In an RPG, players may not see doors, objects or monsters located around the corner in a dungeon. Line of sight is crucial to many types of

video game A video game or computer game is an electronic game that involves interaction with a user interface or input device (such as a joystick, game controller, controller, computer keyboard, keyboard, or motion sensing device) to generate visual fe ...

s, including, but not limited to,

first-person shooter A first-person shooter (FPS) is a video game genre, video game centered on gun fighting and other weapon-based combat seen from a First person (video games), first-person perspective, with the player experiencing the action directly through t ...

s, strategy games,

stealth game A stealth game is a type of video game in which the player primarily uses ''stealth'' to avoid or overcome opponents. Games in the video game genre, genre typically allow the player to remain undetected by hiding, sneaking, or using disguises. S ...

s, and

role-playing video game Role-playing video games, also known as CRPG (computer/console role-playing games), comprise a broad video game genre generally defined by a detailed story and character advancement (often through increasing characters' levels or other skills) ...

s. In simplistic games with a top-down perspective, such as roguelikes, Bresenham's line algorithm can be used to determine line of sight. In first person games such as battlefield and flight simulators an implicit min/max kd-tree may be used to efficiently evaluate terrain line of sight queries. In some live action role-playing games, such as NERO International, the line of sight is used as the duration for some spells and abilities. For example, a ''paralyze'' spell only lasts as long as the target remains within line of sight of the spell's caster. On the other hand, line of sight can be used offensively, like luring a player behind a pillar in order to set a trap - his teammate, being out of line of sight, won't be able to help out until he gets in LoS, which in turn takes time. This time is usually the key moment to strike and go for a kill, if said player falls in said trap. One algorithm for calculating 2-dimensional line of sight is given in the StraightEdge project.

References

{{video game gameplay Video game terminology