Call of Duty game engine mechanics

As with every video game, there is extensive math behind Call of Duty, which decides the outcome of gameplay. This article focuses on the game's mechanics.

Movement and stance
The player's maximum movement speed is dictated by the weapon they spawn with/are holding (depends on game). In all games except Call of Duty, Call of Duty 2 and Call of Duty: Black Ops, movement speed is determined by the weapon the player spawns with. In the aforementioned three exceptions, as well as single player campaign, the weapon currently equipped by the player determines speed.

In addition, there are other factors that affect movement speed.
 * Pistols, SMGs, Shotguns and Sniper Rifles (Modern Warfare 2 only) have a speed of 100%.
 * Assault Rifles, Bolt-Action Rifles and Sniper Rifles have a speed of 95%
 * LMGs have a speed of 87.5%.
 * Riot Shield has a speed of 80%
 * M9A1 Bazooka has a speed of 70%
 * Moving forwards will cause the player to move at 100% their maximum speed.
 * Moving sideways will cause the player to move at 80% their maximum speed.
 * Moving backwards will cause the player to move at 70% their maximum speed.
 * Sprinting will cause the player to move at 150% their maximum speed.
 * Crouching will cause the player to move at 60% their maximum speed.
 * Going prone will cause the player to move at 15% their maximum speed.
 * The Lightweight perk increases all speed by 7%.
 * Aiming down the sights reduces maximum movement speed by 50%. Pistols and SMGs do not suffer this decrease in the Modern Warfare series or in Black Ops.

Stances
Stances are a position that the player's character assumes that has the capacity to affect their movement speed, accuracy, and fire exposure. The three stances have been common to the series since the first game.
 * Standing: The player is fully standing and capable of moving at 100% of their mobility (defined as the base speed multiplied by the movement speed multiplier of the weapon). This stance is also the only stance in which the player can sprint. As a result, this stance is best when on the move or when it is necessary to move from cover to cover. However, while standing bullet spread is increased, and a larger target to the enemy. In addition, standing players make noise when they run, which allows them to be heard by enemies.
 * Crouching: The player is crouched to about half their height, and moves at 60% mobility. While the player moves slower, they are capable of taking advantage of cover that is about waist-height, and their accuracy is increased. Crouching players do not make noise as they walk around, making it the best stance for sneaking up behind an enemy unheard.
 * Prone: The player is prone on the ground, and moves at 15% mobility. The player moves extremely slow, but they present a very small target to the enemy at longer ranges. Accuracy is also best when prone. Prone is best utilized to take full advantage of cover, when taking shots at targets farther away, or in the tactic known as "dropshotting," where a sudden switch to prone in closer combat minimizes damage taken.

Movement

 * Sprint: The player sprints, moving at 150% movement speed for a limited duration. The Marathon and Extreme Conditioning perks increase sprint duration. While sprinting, players are in the stand stance and are unable to perform any action; doing so will stop the sprint. After sprinting for a set duration, players are unable to sprint again until they regain energy. The volume of the player's footsteps is also increased.

In the PC version of all Call of Duty games (With the exception of Call of Duty: Modern Warfare 2), the player is also able to lean left and right to fire from behind cover while presenting a smaller target. Leaning can be done from any stance, but decreases movement speed down to a crawl regardless of the stance. It is not available in console versions due to a lack of mappable buttons, with the exception of the Wii, where the player can lean by twisting the Nunchuk left or right.

Call of Duty: Black Ops introduced the Dive to Prone mechanic, where the player is capable of diving from a sprint to a prone position.

Health
A player's health is determined by the game mode being played.


 * Normal (or Core in World at War and Black ops) mode health: 100
 * Hardcore mode health (or Minuscule in Private Matches): 30
 * Double health (or Oldschool in Call of Duty 4): 200
 * Health regenerates after being hit and not killed, except in Hardcore and Old School, which do not feature health regeneration. The exception to this is in Call of Duty: Modern Warfare 2, which includes health regeneration in Hardcore modes.
 * Five seconds after surviving the most recent damage, ALL health is restored when normal health regeneration is on. When health is restored, the player's character will exhale.

Weapon and Explosive damage
Every weapon in the game deals a set amount of damage. As the range between the player and the target increases, damage is reduced until it reaches a set minimum amount. These charts show each weapons' damages, ranges and reload times, among other things.

Call of Duty: World At War






Modern Warfare 2
Interactive Modern Warfare 2 Flash Chart

Weapon Behavior
There are many more in depth statistics which determine weapon behavior. One of the most important things to take note of is that guns in Call of Duty do not shoot bullets. Instead, they shoot hitscans, which are perfectly straight, infinitely thin lines that travel at an infinite velocity. All hitscans travel forever except for those fired from shotguns, which disappear at a set distance. This means that all weapons in Call of Duty, excluding things that obviously do not use hitscans such as the RPG-7, are perfectly accurate at an infinite range while aiming down the sights. Misses are caused by idle sway, recoil, and lag. Idle sway is the movement of the weapons sights without any input from the player. Recoil is the movement of the sights while firing. Idle sway is simply determined by two numbers; idle amount and idle speed. Recoil is slightly more complex. It is determined by five numbers; maximum horizontal, minimum horizontal, maximum vertical, minimum vertical, and center speed. Each gun has its own set of numbers. Every time a shot is fired, the game randomly chooses two numbers, one for vertical recoil and one for horizontal recoil. These numbers will be in between the weapon's maximum and minimum values for each shot. If a number is positive, it is right or up, and if it is negative, it is left or down. Thus, if a weapon has a positive minimum value or a negative maximum value, it will always kick in that direction. Center speed is how fast the sights reset after firing. It takes effect immediately upon firing, but during fully automatic fire there is usually too much recoil for the sights to completely re-center after each shot. Low recoil is a result of a high center speed, minimum and maximum numbers having low absolute values and balanced values on all sides, and the weapon's rate of fire. Recoil values do not stack, meaning that the next shot fired will kick however much it will kick regardless of whether or not the previous shot has finished kicking. However, because it kicks from wherever the sights were, rate of fire plays an important role. Some weapons, such as the P90, fire fast enough that the high rate of fire actually reduces recoil because multiple shots come out before the gun starts to kick noticeably, while others, such as the MP5, fire slow enough that the next shot will end up coming out at the peak of its recoil, which greatly increases recoil. This was done on purpose to balance weapons so that some could have low recoil and a high rate of fire while others could have high recoil and a low rate of fire. However, this only applies to a weapon's base rate of fire, as that is how the game was balanced. Because of this, using Double Tap will almost always lead to a considerable increase in recoil.

Time to Kill
Time to Kill, usually abbreviated as TTK, is how long a gun takes to kill an enemy from the time the trigger is pulled until the target is dead. In many role-playing games, players use damage per second, or DPS, to determine a weapon's effectiveness. However, in a shooter such as Call of Duty, where everyone has equal health and firefights are very fast, it is far more beneficial to determine TTK than DPS. To calculate a weapon's TTK, all that is needed are damage values and the delay between shots. For example, a gun that fires at 750 RPM has a delay between shots of .08 seconds. If that gun does 30 damage, it takes four shots to kill. The first shot comes out the instant the trigger is pulled, so the formula for determining a weapon's TTK is d(s-1), where d is the delay between shots and s is the number of shots needed to kill. This means that any weapon that kills in one shot will technically kill in zero seconds flat. Because most weapons lose damage over range, it can be necessary to perform multiple TTK calculations for a single gun. Beware that even a few missed shots will greatly increase a weapon's TTK, so it can be beneficial to plug in different amounts of misses using the formula d(s-1+m), where m is the number of misses. Weapons with low recoil are the most likely to actually reflect TTK with no misses.