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 ''WarGames'' is a 1983 American Cold War science fiction techno-thriller film written by Lawrence Lasker and Walter F. Parkes and directed by John Badham. The film, which stars Matthew Broderick, Dabney Coleman, John Wood, and Ally Sheedy, follo ...
and some
role-playing game A role-playing game (sometimes spelled roleplaying game; abbreviated RPG) is a game in which players assume the roles of characters in a fictional setting. Players take responsibility for acting out these roles within a narrative, either through ...
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 A PC game, also known as a computer game or personal computer game, is a type of video game played on a personal computer rather than a video game console or arcade machine. Its defining characteristics include: more diverse and user-determined g ...
to implement line of sight graphics was ''
Dungeon , Ireland A dungeon is a room or Prison cell, cell in which prisoners are held, especially underground. Dungeons are generally associated with medieval castles, though their association with torture probably belongs more to the Renaissance period ...
'', which was played on a PDP-10 mainframe computer (1975).


A tank 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 crawl, dungeon. Line of sight is crucial to many types of video games, including, but not limited to, first-person shooters, strategy games, stealth games, and role-playing video games. 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 k-d tree, 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.


{{video game gameplay Video game terminology