VATS (Fallout 4)



V.A.T.S. or the Vault-Tec Assisted Targeting System is a statistic-based combat system

Characteristics
Using V.A.T.S. slows down time, creating a "bullet time" effect. V.A.T.S. reduces incoming damage received by the player. Actions queued in V.A.T.S. can be canceled, and being in V.A.T.S. is required in order for the player to make a Critical Hit. Random critical hits are possibly only via certain perks and chems.

The V.A.T.S. display shows the predicted hit probability of the attack. The V.A.T.S. display also shows the predicted damage if a hit is scored, by shading the portion of the target's health bar that would be reduced. (This prediction is not always accurate however). The V.A.T.S. controls allow the player to move between targets and (for ranged attacks) between body parts. Attacks can be queued on multiple targets or on the same target.

The V.A.T.S. display shows an action point bar (see below) which gives feedback on the maximum number of attacks that can be queued with the currently selected weapons. This includes time/action points required to load or reload the weapon. Each action - attacking or loading/reloading - is shown as a continuous colorful section in the action point bar.

Critical hits
Attacks in V.A.T.S. charge up a critical hit bar, the rate of which is primarily influenced by Luck. Once the critical meter bar is full, the player can elect to upgrade an attack to a critical hit. Critical Hits are guaranteed to hit, regardless of the actual V.A.T.S. percentage hit chance, provided that chance is above zero. Critical hits also bypass Damage Resistance and Energy Resistance. Once used, a critical hit must be replenished by recharging.

Ranged
Ranged attacks in V.A.T.S. can select a specific body part of the target. The V.A.T.S. display shows the predicted accuracy for each individual body area. The body areas available vary depending on the type of creature being attacked. Attacks can be queued on the same body part on the same target, or different body parts on the same target, as well as on multiple targets. Effects of hitting a specific body part vary depending on the creature being attacked. For example, there may be different multipliers for damage, for crippling effects, etc.

These effects are not shown in the V.A.T.S. display. The current health of each body part is shown in the display, as a smaller health bar. That body part is fully crippled when its health bar reaches zero. V.A.T.S. can then be activated to manually target and shoot throwable weapons, detonating it at the desired point of its trajectory, if a hit is scored.

Melee
Melee attacks in V.A.T.S. do not target a specific body part, but the entire target creature only. They may only be queued up against targets that are currently within melee range, with the Blitz perk increasing the range significantly. 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.meter. The Critical Banker perk allows storage of more than one Critical Hit.

Cost per attack
The amount of Action Point consumption per attack is based on the base weapon type and the mods fitted to it. For automatic weapons, the action point cost is for one burst (usually 3 rounds), while for most other ranged and melee weapons, it is for single shots or single attacks. There is a dramatic difference in the amount of V.A.T.S. points used per attack depending on the stock, barrel and sighting devices attached to the same weapon. For example, scopes greatly increase the number of points consumed per attack, while reflex sights decrease the amount. V.A.T.S. will only allow up to 16 attacks to be queued.

Weapon modifications

 * Receivers – Receivers greatly impact the rate of attacks in V.A.T.S. A non-automatic receiver that increases the rate of attacks in V.A.T.S adds a "Light," "Hair Trigger" or "Advanced" prefix to the weapon name when fitted. Automatic receivers consume significantly more AP per attack, but will fire in bursts at a cost of reduced accuracy and range.
 * Barrels – "Short" and "Light" prefixed barrels lower AP cost in V.A.T.S. while reducing recoil. "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 reduce AP cost; "Large" and "Drum" prefix magazines increase AP cost.
 * Sights – "Standard" prefixed sights slightly increase 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 (crouching), their body will block V.A.T.S shots on their head, despite it being closer.
 * If an environmental effect causes the player character to move horizontally while in V.A.T.S. (e.g. by 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.
 * 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.