Hitscan

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In first-person shooter games, a hitscan weapon is one that, when fired, instantly hits whatever the weapon is pointing at. This is in contrast to projectile weapons, which fire projectiles that take time to travel.

[edit] Examples

One of the most well-known examples is the railgun in the Quake series. The advantage of hitscan weapons is that because they hit instantly, there is no need to lead the target (to aim slightly ahead of a moving target in order to compensate for the time it takes for the projectile to reach it).

Some popular examples of hitscan include Unreal Tournament's shock rifle (primary fire), sniper rifle, minigun, and lightning gun (which was introduced in UT2003 as a replacement to the sniper rifle, and then featured again in UT2004 alongside a newly invented sniper rifle) and the machinegun, shotguns, and railgun in the Quake series. In the original Unreal Tournament, the shock rifle uses both the hitscan and projectile methods. The weapon hits the target immediately, but a laser travels towards the target even after the bullet has hit something. This can be seen easily in slower gameplay, and when firing at objects farther away. This was fixed in Unreal Tournament 2003 and Unreal Tournament 2004, where the visual tracer and hit detection are synced, making it much easier to determine that the player had hit an enemy.

[edit] Real world analogies

Hitscan weapons are purely abstractions; instantaneous travel is impossible in the real world. There are, however, a few real world analogues to hitscan. At close ranges, guns appear to act like hitscan weapons because the bullets they fire move so quickly that they appear to hit their target instantly. However, at longer ranges, targets must be led with guns. This is not true hitscan, but nonetheless many older games model guns as hitscan weapons for performance reasons, since hitscan is a reasonable approximation at short ranges seen in most shooter games. The timespan, however, between perceiving and reacting, makes even real instant reactions impossible.

A closer analogy is a lasertag weapon, which fires a harmless laser beam. The laser beam travels at the speed of light, which is the fastest way that information can be transmitted. This is actually faster than a hitscan shot in computer games, since a computer can not process all necessary commands as fast as light travels from one point to another. The time which a packet takes to travel from one computer (called latency, but informally referred to as 'lag') to another also makes a real instant hit in computer games impossible.

A similar analogy is how light photons appear when they travel from their source. Human beings perceive a room to be lit as soon as a bulb is bright because the photons travel at the speed of light. In a similar way, the effects of hitscan weapons are practically instant and hit or miss as soon as the computer has calculated their path.

[edit] Games entirely without hitscan weapons

With advances in netcode and graphics processing, it became possible to simulate the ballistic nature of real-world firearms using "projectile" models with extremely fast velocities, rather than relying on "hitscan" models. This adds elements of long-range deviation to what used to be "on-the-dot" targeting in many FPSs.

In Operation Flashpoint: Cold War Crisis, all the rifles and submachine guns are projectile weapons; as a result, the player must lead the target when firing from a very long distance. The same is true in the Delta Force series of games, as well as Red Faction, although in the latter case the effect is only perceptible on very large maps. The recent games Battlefield 2 and Battlefield 2142 by EA Digital Illusions CE do not include hitscan weapons, compared to its predecessors Battlefield 1942 and Battlefield Vietnam. Absolutely all the weapons, handheld or mounted on a vehicle, in both Red Orchestra and PlanetSide are projectile weapons. In Killzone: Liberation all weapon projectiles travel significantly slower than their real world counterparts; this allows the player to dodge many attacks, making game play more feasible under the limited range of the isometric third person view.

In the arcade game Silent Scope, the rifle is a projectile weapon, with external ballistics grossly exaggerated for gameplay. In some Third-Person Shooters, like the Max Payne and Hitman series, the firearms are also projectile weapons; the former (and games resembling it) takes advantage of this mechanic with its "bullet time" gameplay, where time is nominally slowed-down (revealing bullet trails and shockwaves) but the player can aim at normal speed.