What is "hitscan"

Hitscan is a term that is used mainly in computer games, most commonly in first person shooters. A hitscan is a calculation performed by a game to find the point at which a given line intersects a game object, and is commonly used to determine whether a bullet or projectile hit a target after being fired from a weapon.

A projectile weapon which uses unmodified hitscan information to dictate whether or not it has hit its target is often called a hitscan weapon. Deploying the weapon calls the hitscan function, and if an object is detected in the path of the projectile, a hit is registered. Since the effect is immediate, the projectiles effectively travel at infinite speed and have a linear or otherwise simple trajectory — a practical approximation of a bullet's speed and accuracy over short distances. To improve the realism, programmers may use hitscan functions in slightly different ways - for example, applying a random perturbation to the calculated path to simulate inaccuracy. As another example, the assault rifle in Half-Life 2 calls a hitscan function in the middle of a 'blazing gun' animation, creating a small amount of lag between weapon deployment and the hitting of the target to better approximate real-life ballistics.