Penetration (PV)

PV or Penetration Value or is a value assigned to all weapons and plays a key part in damage calculation during attacking.

A penetration is a single application of a weapon's damage dice against the target. One attack might result in multiple penetrations, multiplying the weapon's damage dice accordingly. In game, penetrations are noted in the message log as a parenthetical multiplier after the damage, such as or.

Background
There are two components to an attack.
 * The first component is the hit. If an attacker's to-hit roll (heavily influenced by Agility) succeeds, the attack hits and applies on-hit effects.
 * The second component is penetration. If an attacker's penetration roll (heavily influenced by Strength) succeeds, the attack penetrates and deals damage.

For more general information about attacking, refer to the relevant combat mechanics page:
 * Melee combat
 * Missile weapon combat
 * Thrown weapon combat

How PV Is Displayed
A weapon's PV is displayed in game in one of the following ways.

Note that the descriptions above apply only to the value that is displayed in the game UI. For the purposes of actual PV calculations, as described in the sections below, the game subtracts 4 from the values that are shown in the UI. So, for example, the fullerite maul pictured above has a penetration value of 2 for the purposes of all in-game calculations. (vibro weapons are an exception to this rule.)

Melee Weapon PV Calculation
The PV of melee weapons is calculated as the follows:
 * Base penetration bonus,
 * For non-vibro weapons, the base penetration bonus is equal to the weapon penetration value shown on the equipment screen in-game, minus 4. For example, if the weapon shows 7, your base penetration bonus is 3. Typically this bonus is the same as your strength modifier (or your strength modifier + 1 for two-handed weapons), but it can be capped to a lower value depending on the weapon.
 * For vibro weapons, the base penetration bonus is always equal to the defender's AV.
 * +1 bonus penetration if the weapon has the Sharp modification,
 * +4 bonus penetration if the enemy is asleep,
 * +1 bonus penetration to swarmer attackers for each additional swarmer enemy that surrounds their opponent,
 * and additional bonus penetration from the Charge, Lunge, Long Blade Proficiency, Improved Aggressive Stance, Shank, or Slam skills as applicable.

A critical hit is guaranteed one penetration regardless of PV if the source of the critical hit is the player character.

Ranged Weapon PV Calculation (Non-Bows)
Ranged weapon PV is determined by the PV of the gun itself. The PV of the bullet does not matter and remains static no matter what ammo is loaded into the gun.

Critical hits on ranged weapons add a flat +2 PV to the shot, increased to +4 if the weapon is a pistol and the user has Dead Shot.

Ranged Weapon PV Calculation (Bows)
A bow's base PV is determined by the PV of the arrow loaded into the bow. The also has the effect of adding the wielder's strength modifier to the penetration value. The adds +4 PV to the shot and then adds the wielder's strength modifier to the penetration value.

Whether or not these PV modifications are shown in game currently seems to be somewhat inconsistent. For example, the always show 4, but the compound bow's PV will update accurately based on the ammo loaded into it and the wielder's strength.

Thrown Weapon PV Calculation
Thrown weapon PV is calculated as follows:
 * 1) Start with a base penetration of 5.
 * 2) Add the thrower's Strength Modifier, up to but not exceeding the PV () value shown on the thrown item in game.
 * 3) * A negative strength modifier cannot reduce this value below 5 for thrown weapons.
 * 4) * Objects that aren't explicitly thrown weapons have a maximum PV value of 6.
 * 5) Minus 4 from the calculated total
 * 6) * Similar to melee weapons, the thrown weapon PV used for internal calculations is always 4 lower than what is displayed in game.

Penetration Formula
- Roll the attacker's PV value against the defender's AV value 3 times (let's call this a triplet).
 * - Each individual roll within the triplet works as follows (let's call each roll a singlet):
 * - Roll . Each time that the maximum result of   is rolled, perform the   roll again and continue adding the results together.
 * - Add the attacker's PV value to the total roll calculated in.
 * - Note whether the total PV roll from is greater than the target's AV.
 * - If at least one singlet roll was greater than the target's AV, the attack penetrates one time (or one more time if this is a subsequent triplet). If all three singlet rolls were greater than the target's AV, reduce the PV value by 2, return to, and perform another triplet of rolls to determine if the attack penetrates an additional time. (Continue this loop, reducing PV by 2 each time, until at least one singlet fails to roll higher than the target's AV.)

In summary, the attack penetrates and deals damage equal to its damage dice once for each triplet of rolls where at least one singlet was higher than the target's AV.

If all three rolls in the first triplet are equal to or lower than the target's AV, the attack fails to penetrate at all.

Penetration vs. AV Chart
The following chart shows the chances to penetrate against a creature depending on the relative value of attacker's PV versus the target's AV. Keep in mind that this chart corresponds to the internal PV value of a weapon. For example, the internal PV of a 7 weapon is 3, so a 7 weapon versus a creature with 2 would correspond to the +1 PV column of this chart. Similarly, the internal PV of a 4 weapon is 0, so a 4 weapon versus a creature with 4 would correspond to the -4 PV column of this chart.

Once your PV equals or exceeds the target's AV, each +2 extra PV will ensure one additional penetration against the target.