VATS



V.A.T.S. (Vault-Tec Assisted Targeting System) is a visually dynamic, stat-based combat system in Fallout 3, Fallout: New Vegas, Fallout 4 and Fallout 76.

Background
Although known to be a product of the Vault-Tec Corporation, the developmental origins of this advanced combat technology have been lost to time. However, it was available to the Pioneer Scouts and their parents, in the event their parents became inebriated and could not aim correctly.

By 2287, the Robotics branch of the Institute had managed to receive permission from Father to enhance the capability of a Generation 3 synth brain, creating an emulation of V.A.T.S. accessible to Gen-3 synths. 

Fallout 3
While using V.A.T.S., the otherwise real-time combat is paused. Various actions cost Action Points, and the user can target specific body areas for attacks, inflicting specific injuries.

When using V.A.T.S. against a humanoid enemy, seven different areas can be targeted: the head, torso, left arm, right arm, currently held weapon, left leg, and right leg. However, there may be other points available when facing off non-humanoid creatures (e.g. robot combat inhibitors, ant antennae).

When targeting a part, the screen displays a percentage of how likely the attack will hit the targeted area based on distance from the target, visibility of the targeted body part, and combat skill. The percentage of a hit cannot be any higher than 95%, so there is a small 5% chance to actually miss. A higher percentage does not equate to more damage done; for example, an 95% hit to the head will not do more damage than an 80% hit to the head. The readout also displays the overall condition of the body parts on the target. The bar will be empty when the limb has been crippled.

V.A.T.S. also displays a health meter indicating the target's overall health, as well as an indicator showing the amount of damage a V.A.T.S. attack round using the character's current weapon will inflict. Note that the indicator shows the weapon's maximum non-critical potential damage that the weapon would do if the character's relevant combat skill (e.g. Small Guns) were at 100. If the character's combat skill is less than 100, they will do less real damage with each attack than what the V.A.T.S. indicator shows. On the other hand, achieving a critical hit (such as a Sneak Attack Critical) can potentially produce more real damage than the indicator shows.

There is a 15% boost in the chance for a critical hit in V.A.T.S. mode, but weapons degrade at 4 times the regular rate.

Unlike previous Fallout games, it is not possible to target the eyes or groin, nor target any individual body parts in melee and unarmed combat. However, one can still strike specific limbs without aiming for them, and still cripple and dismember enemies. Also, unlike in previous games, children cannot be targeted.

Effects
Although body part damage can be achieved through manual aiming, V.A.T.S. allows more effective targeting of particular body parts. Crippling any body part will result in the target momentarily pausing to clutch the now crippled body part or reel from the injury. When using explosive and melee weapons specific body parts cannot be targeted while in V.A.T.S. The enemy is simply targeted as a whole. The effects of crippling specific body parts are listed below.
 * Crippling the head will reduce overall accuracy and Perception (-4) of the target. If inflicted upon the player character, the screen will intermittently get fuzzy and a ring will be heard through the speakers, loosely simulating the effects of a concussion.
 * Crippling the torso will result in the target flinching far more often from shots than normal. This can also affect the player character, throwing off aim and interrupting attacks.
 * Weapon accuracy is reduced in V.A.T.S. by a crippled arm, but still, allow using weapons. In the first-person mode, the held weapon will sway, and while this may not seem to affect the accuracy with regular non-V.A.T.S. shots, it does make the crosshairs sway significantly while using the scopes on weapons like a sniper rifle or scoped .44 Magnum, making it much harder to aim. A crippled right arm also reduces base melee damage done by 10% if wielding a one-handed weapon. If wielding a two-handed weapon (or unarmed), one crippled arm reduces base damage done by 5%, two crippled arms reduce base damage done by 10%.
 * If it is an explosive ordnance (like a frag grenade), it will explode, dealing its damage to the target holding it (and any others nearby). Grenades can be targeted by V.A.T.S. while in the air after being thrown as well. If successfully hit on the fly, they will explode prematurely.

Bugs

 * On rare occasions, the black-and-white effect of V.A.T.S. will carry over to the normal game, rendering everything except the HUD in a permanent grayscale filter.
 * If the player falls from a great height, he/she can pull out a melee weapon and target someone below. The effect of being teleported into range loses all velocity from the fall and negates the damage. This is most easily seen at Tenpenny Tower, from one of the balconies onto citizens below.
 * Firing weapons that require two shells, such as the Double-barrel shotgun, while possessing only one can lead to a bug in which the character does not actually fire a shot in V.A.T.S. It will just result in a drawn-out cinematic view of the player aiming at his/her target.
 * Occasionally, the game will freeze during a V.A.T.S. attack. On consoles, this will cause the screen to become stuck and the console will need to be reset. On PC, the game will automatically close (sometimes after a short period of time). There is no fix, so it is recommended that players save often to avoid loss of progress.
 * Occasionally a bug can occur with most V.A.T.S attacks in which V.A.T.S. will jump out of slow motion and fire each shot extremely rapidly. This usually winds up with a live enemy and no AP.

Bugs

 * On occasion, a target in V.A.T.S. will show 0% to hit or not show any percentages to hit at all, despite being perfectly valid (which can be verified by selecting attacks, which ordinarily should not be possible). Leaving and re-entering V.A.T.S. or switching targets can help fix this.
 * Upon tapping the V.A.T.S. button, the player may only hear a click and no change in gameplay, as V.A.T.S. does not activate. This problem can last for up to several minutes (easily enough to hinder any player reliant on the V.A.T.S. system), at which point V.A.T.S. once again becomes available. This issue appears to be a problem with the L2 & R2 button mapping. Remapping V.A.T.S. to a different button can resolve the issue. If this doesn't work, you can turn off the controller and turn it on again or even quit the game and get back in.
 * V.A.T.S. targeting is bugged for certain guns - most lever-action rifles and a few pistols: it consistently shoots high, making headshots improbable or impossible. Consistently replicable by starting a new game, adding a brush gun (id: 00121148) and .45-70 ammo (id: 0013e43e), forcing Guns to 100, and shooting at Easy Pete's head from the nearby road. Bullet impacts will appear on the windowpane behind him - and, shot after shot, will consistently be high. Modifying the gun to have perfect accuracy and/or setting fVATSSpreadMult to 0.01 will reveal that the V.A.T.S. point of aim is roughly a foot high. No known fix yet. This bug also seems to occur with the Hunting Revolver.
 * A reloading glitch can rarely occur where the player is granted a 100% boost in reload speed after a target is killed in V.A.T.S. and the cinematic death animation plays simultaneously as the player is reloading (namely the single shotgun) the effect lasts until the player enters another cell, switches weapons, dies, or reloads a previous save.
 * When using Melee/Unarmed, it is possible to get stuck in a wall, You will have to reload a previous save, use fast travel, or use a console command.
 * By tapping the V.A.T.S. button (regardless of whether an enemy is around), the game freezes to the point in which a manual restart is necessary. Restarting (from the same save point) has not fixed the glitch, but loading an earlier save might. Try deleting the system cache.
 * After choosing where you want to attack at your enemy and pressing the button to attack them, your character may do nothing and stay still during the slow-motion for an unconfirmed amount of time. On most occasions, you will either die or lose a large portion of your health. It is largely related to attacking in V.A.T.S. while you were reloading, so make sure ALL reloading animations and sounds are totally complete before you attempt a V.A.T.S. attack. This can also occur with the mysterious stranger if his target is killed prematurely by you, or another NPC. He will not fire his 6 rounds and V.A.T.S. will not end until 15 seconds or more.
 * On very rare occasions, your character may not fire after queuing up the attacks, forcing you to reload a previous save.
 * At close to medium range, V.A.T.S. may simply refuse to register attacks but will go into cinematic view. The Player Character will simply stand still while being attacked. Note: The enemies will go back to normal speed which means if you are in a difficult fight, you just might die. After several seconds, however, the screen may revert to the normal view. This may happen repeatedly on PS3 while using the Brush gun.
 * After entering V.A.T.S., and skipping the kill camera, your game may be in slow motion for about ten seconds. This won't prove any difficulties, everything will be in slow motion. This may also occur if you have the cinematic kills on and usually occurs around areas with cliffs, apparently.
 * A similar bug may occur on PC, but under different circumstances. This seems to happen if your companion kills an enemy you're about to kill in V.A.T.S. In this case, the kill will happen at normal speed, but the slow-motion effect will persist. This may only happen when Veronica is the player's companion.
 * While attacking in V.A.T.S., only the target and player will be in slow motion. Any other enemies in the area will move and attack at normal speed, making you a prime target for the duration of your attack.
 * Sometimes the camera may zoom on the enemy and all your shots may fire in quick succession as if you're using an automatic weapon, but no shots will register on the target and will cause zero damage.
 * When attacking an enemy in/underwater with a melee weapon, if you're in close range, the game will most likely freeze and you will have to load an earlier save.
 * Rarely, after exiting V.A.T.S., if "true iron sights" is turned on, the player's default weapon position may be locked in iron sights. This can easily be fixed by zooming in.
 * When using the recharger pistol, recharger rifle or MF Hyperbreeder Alpha in V.A.T.S., if the number of attacks exceeds the amount of ammunition in the rifle's magazine, it will fully recharge the rifle minus every attack selected after the recharge.
 * Sometimes in V.A.T.S., if queuing up attacks with a firearm and attacking, the player will not do anything and can still be attacked. However, AP is not lost when going out of V.A.T.S. after a few seconds.
 * V.A.T.S. targeting can sometimes cause the screen to move and limit the options available to the player. This is most common when enemies are too close. A similar but possibly related issue can occur at range when body parts are shown in V.A.T.S. but cannot be targeted because the limb selection option won't appear for certain limbs (most common when targeting small objects like antennae).

Fallout 4
While largely similar in Fallout 4, V.A.T.S. went through some changes. Instead of freezing time as in previous games, V.A.T.S. significantly slows time.

Actions queued in V.A.T.S. can now be canceled before they are taken.

Melee and V.A.T.S.
Melee player characters only benefit from critical hits while in V.A.T.S. They can queue up attacks on multiple opponents with the slowed time benefit, so long as targets are in range. With the Blitz perk, this becomes less of an issue; with Blitz, that base damage gets multiplied by the distance, then sneak attack and critical bonuses for massive damage. Sneak build player characters can score a critical hit on a sneak attack along with the Blitz perk, which will let one deal even more damage. An enemy may use a melee attack during the V.A.T.S. sequence and stagger the player character, causing them to drop out of V.A.T.S.

Explosives and V.A.T.S.
As opposed to its predecessors, thrown explosives like the Fragmentation grenade cannot be directly used in V.A.T.S., since grenades are not equipped as primary weapons anymore. Grenades can be used in conjunction with V.A.T.S. by throwing them outside of V.A.T.S (one can use the Demolition Expert perk at rank 2 to get the throwing arc for precision attacks), then entering V.A.T.S. and shooting the grenade by targeting it in its flight path.

Critical hits
Critical hits are no longer randomized; instead, attacks in V.A.T.S. charge up a critical hit bar, the rate of which is in part influenced by Luck. At 10 luck, one can expect it to take about 5 hits to build the critical meter to full. The Critical Banker perk allows storage of more than one Critical Hit. Once full, a player character can choose which of their shots will be upgraded to a critical. Critical Hits are also guaranteed to hit, regardless of the actual V.A.T.S. percentage hit chance. Once used, the critical hit drains the bar and it must be recharged before another critical hit can be made.

Cost per shot
The amount of Action Point consumption and critical damage a weapon will do is based on the weapon type and ammunition type; .50 caliber sniper rifles deal more critical damage, and 10mm pistols are capable of achieving 8.4 Action Points per shot. All mod AP costs stack by direct addition. Rate of Fire is the biggest indicator of how many shots one can queue in V.A.T.S.

For automatic weapons, the rate of fire will increase the amount of bullets/lasers/bolts/etc. and AP cost per burst, while on a semi-automatic or bolt-action weapon, it is for single shots. There is a dramatic difference in the amount of V.A.T.S. points used per shot between various types of stocks and aiming devices attached to the same weapon. Scopes increase the number of points consumed while reflex sights decrease the amount.

V.A.T.S. will only allow up to 16 shots to be queued.

Weapon modifications

 * Receivers – Receivers greatly impact the rate of fire. A non-automatic receiver that "increases the rate of fire," has a "Light", "Hair Trigger" or "Advanced" prefix, will reduce AP cost in V.A.T.S. Automatic receivers consume more AP but will fire in bursts at a cost of reduced accuracy and range. "Armor-Piercing," "Calibrated " or "Heavy" prefix, and any receiver that increases range, damage, and accuracy, will raise AP cost. Gun Nut and Science! perks are needed to produce a mod for a weapon that both conserves AP cost and deals high damage.
 * Barrels – "Short" and "Light" prefixed barrels lower AP cost in V.A.T.S. while reducing recoil, making them useful for close-quarters combat. "Long" and "Heavy" prefix barrels increase AP cost in V.A.T.S. and the effective range of a weapon.
 * Stocks – For rifles, a "Short" prefix stock reduces AP cost in V.A.T.S. at the expense of increased recoil. For handguns, a marksman's grip slightly lowers AP cost.
 * Magazines – "Quick Reload" prefixed magazines reduces AP cost; "Large" and "Drum" prefix magazines increases AP cost.
 * Sights – "Standard" prefixed sights slightly increases the AP cost. "Reflex" prefixed sights reduce the AP cost to fire the weapon in V.A.T.S. All scopes double AP cost.
 * Muzzles – Muzzles do not impact the AP cost of shots in V.A.T.S.

Bugs

 * When targeting an enemy in V.A.T.S., if they are attacking the player in close quarters while the player is sneaking, their body will block V.A.T.S shots on their head, despite it being closer.
 * If the player character moves horizontally while in V.A.T.S. (like when standing on a moving platform), the camera will remain in the same location despite the character moving. The camera will return to the player when they exit V.A.T.S.
 * V.A.T.S. attacks will often be skipped over when used against any variant of radscorpion.
 * Melee attacks on V.A.T.S. on a big creature, namely Deathclaws, under a tree (or similar environments), may rarely shoot the creature up in the air.
 * Sometimes when engaging V.A.T.S., it will actually cause the game to black screen or V.A.T.S. and the game to freeze. It can be closed by pressing the Windows key, hovering to the taskbar, and closing the Fallout 4 task.
 * When pressing the V.A.T.S. button while no valid target is near the V.A.T.S. sequence may sometimes activate anyway yielding no targets.
 * The time slowdown effect of V.A.T.S. does not affect the player's reload speed. The sounds may become distorted but the reloading sequence itself will progress normally.

Fallout 76
V.A.T.S. appears in Fallout 76. Due to the online multiplayer nature of the game, V.A.T.S. does not slow or stop time when activated, instead functioning as an aim assistant. The new real-time V.A.T.S. system provides the unique advantage of being able to move around while using it; enemies will keep moving in real time too, though, making the player character more vulnerable to attacks than in previous iterations. Another consequence of the real-time combat is that it is possible for opponents to dodge the attack (as if the player character were aiming manually), making V.A.T.S. more effective at close-range. It also leaves player characters more vulnerable to attacks than in previous games.

Actions cannot be queued and are instead taken immediately after selecting a target's body part and attacking it. V.A.T.S. actions use up Action Points like in previous iterations and cannot be used very frequently at early levels since all player characters start with 1 Agility.

The critical meter from Fallout 4 returns, allowing one to make a critical strike on an opponent by pressing the button shown in the V.A.T.S. screen if the bar is full. However, unlike Fallout 4, attempting to activate V.A.T.S. multiple times in a row will also drain available AP. This hinders using V.A.T.S. to "scan" for enemies.

Bethesda Pinball
V.A.T.S. appears in the Fallout pinball table of Bethesda Pinball. Because it is based heavily on Fallout 4, use of V.A.T.S. slows down time instead of temporarily pausing the game. Its use is governed by a red meter shown next to the main right flipper that slowly fills as the player attacks enemies, but can instantly be refilled when VATS is spelled on the table's four upper rollovers. V.A.T.S. is used in combat to deal exceptional damage to one particular enemy and is activated by holding down the launch button when the V.A.T.S. meter is full, choosing an enemy to use it on with the flipper buttons and then pressing both buttons simultaneously to use V.A.T.S. on the targeted enemy. There are two perks that enhance the V.A.T.S., obtained from successfully completing certain Vault missions: a Perception bobblehead that fills the V.A.T.S. meter faster and an Agility bobblehead that grants more points every time V.A.T.S. is used. Using it twenty times in a single session grants an extra ball.

Behind the scenes

 * V.A.T.S. was partially inspired by the ability to target specific limbs in the turn-based combat system of Fallout and Fallout 2.