Fallout: New Vegas Combat

Fallout: New Vegas has a combat system that is very similar to its' predecessor, Fallout 3.

V.A.T.S.
 The Vault-Tec Assisted Targeting System returns to Fallout: New Vegas allowing the player to freeze combat and specifically target six different limbs at the cost of action points. It is mostly unchanged in principle from Fallout 3, although arguably weaker.

Changes

 * Every melee weapon has a special attack, which can be selected using the triangle, Y button, or R key on the PS3, Xbox 360, and PC respectively.
 * Unarmed weapons gain uppercut and cross at skill levels 50 and 75. These special attacks have an AP cost of 20 regardless of the weapon used.
 * All melee/unarmed damage (except thrown melee weapons) dealt by the player is automatically doubled.
 * You take 75% damage in V.A.T.S. instead of 10%. Dying in V.A.T.S. is a very real possibility.
 * The V.A.T.S. critical chance bonus is 5% instead of 15%.
 * There is no longer any weapon durability penalty for V.A.T.S. attacks.
 * Enemies are less aggressively slown down; while all enemies move slower in V.A.T.S., those not actively targeted are not slowed nearly as dramatically.

Aim down sights
A new feature in Fallout: New Vegas allows the player to aim down the sights of their firearm, as opposed to in Fallout 3 where the "aim down sights" was simply a zoom in feature to the side of the weapon.

Combat damage
Damage calculations that follow are not to be taken as 100% accurate. There are various exceptions in how certain modifiers get included (most notably DT), so this is intended to be a general guide.

First, Dam needs to be calculated, where:
 * $$Dam=Dmg \times Skill \times Cond \times MeleeVats + Bonus$$


 * Dmg = Unmodified, base weapon damage, as seen on individual weapon pages.
 * Skill = A modifier ranging from .5 to 1, as seen for the Fallout: New Vegas skill formula.
 * Cond = A modifier ranging from .5 to 1, based on weapon condition.
 * MeleeVats = If the player is using a melee or unarmed attack, this is set to 2, otherwise, this is set to 1.
 * Bonus = The player's strength bonus (if using melee), unarmed bonus (if using unarmed), or 0.

Second, any critical damage (if a critical roll succeeded) and armor is added in, where:
 * $$Dam_{adjusted}=(Dam \times DR) + isCrit \times (Critdmg \times BC) - DT$$


 * DR = A number ranging from 1 to .15, representing the Damage resistance of the target.
 * isCrit = 0 or 1, 0 if is not a critical hit, 1 if it is.
 * Critdmg = Unmodified critical bonus damage, as seen on individual weapon pages (may be 0).
 * BC = 1.5 if having Better Criticals, 1 otherwise.
 * DT = The Damage threshold of the target. Note that this number cannot reduce Dam (net any critical or resistance modifiers) to less than 20% of its value, see the DT page for details.

Finally, any other multiplicative modifiers are included, such as:
 * $$Final\ damage=Dam_{adjusted} \times SA \times HS \times AM \times DM \times Perks ...$$


 * SA = Sneak Attack modifier adds +100% total damage
 * HS = Headshot modifier adds +100% total damage
 * AM = Ammo type multiplier (such as from hollow-point variations).
 * DM = Difficulty multiplier. 1 on normal difficulty, 0.5 on very hard.
 * Perks = Other damage multipliers from perks such as Lord of Death, Bloody Mess and Living Anatomy
 * ... = Anything else, like Chems or possibly special melee attacks.