Fallout 2 Ranged Combat

Fallout 2 Ranged Combat involves many complicated formulas. The goal of this article is to list them in an understandable way for the average player.

Chance to Hit
The equation below is a general equation for a Chance to Hit. The game takes into account many other factors, like blindness or if the target is laying on the ground. It also applies different bonuses to Perception for all characters. Chance to Hit = (Weapon Skill + 8*(Perception - 2) + Weapon Perk - (4*Distance to Target) - (Target AC + Ammo AC modifier) + Lighting Penalty + STR requirement penalty + Aimed Shot Penalty) * ((100 + Combat difficulty modifier) / 100)

Please note that:
 * Penalties and Ammo AC modifier are negative numbers and need to be subtracted.
 * Apart from the Weapon Long Range perk discussed below, there is also the Weapon Accurate perk that gives +20% chance to hit.
 * Not fulfilling a weapon's Strength requirement results in -20% Chance to Hit for each point of Strength that is missing.
 * Aimed Shots have a penalty depending on the targeted body part; the penalty's amount is added to Critical Chance.
 * Combat difficulty modifier depends on the game's difficulty level, it is +20 on Wimpy and -20 on Rough and affects only enemies.
 * Chance to Hit is capped at 95%.

Weapon Long Range perk
For any weapon with Weapon Long Range perk, the bonus from perception and the distance penalty is :

If Range < (PE-4)*2, only available when PE >= 5: ToHit = PE*8 ''Notice that being within a certain range results in no distance penalty. The Chance to Hit remains the same.'' If Range >= (PE-4)*2: ToHit = (PE-2)*16 - Range*4

Lighting penalty
Lighting penalty is defined by how well the target is illuminated. Different light sources give light of different intensity, but only four light levels exist $$ Check image to the right for comparison between a flare and the player character.

The four light levels are:
 * 0% penalty - fully illuminated, just like during the day
 * 10% penalty
 * 25 % penalty
 * 40% penalty - total darkness

With the Night Vision perk, lighting penalties change to:
 * 0% penalty
 * 10% penalty
 * 25 % penalty - for total darkness

In caves, the maximum light penalty is only 10%, even during nighttime.

Damage calculation
Below is an equation that tries to generalize the steps that the engine does to calculate damage. A = int((weap_dmg + bonus_dmg) * (ammo_dmg_1 / ammo_dmg_2) * crit_multi * (combat_diff / 100)) - int(DT_armor / weap_pen or armor_pierc)

B = int(A * (min((DR_armor + DR_ammo) / armor_pierc, 90) / 100)

Damage = A - B Please note: Variables:
 * function int is the same as trunc, it means to round down, for example int(4.7) = 4
 * min(x, y) means picking a smaller value; max(x, y) means picking a bigger value
 * "min((DR_armor + DR_ammo), 90)" means that DR is capped at 90%
 * weap_dmg - random damage value produced from weapon's damage range
 * bonus_dmg - bonus damage from perks
 * ammo_dmg_1 - dividend of the ammo damage multiplier
 * ammo_dmg_2 - divisor of the ammo damage multiplier
 * crit_multi - critical hit damage multiplier from critical hit table
 * combat_diff - combat difficulty multiplier; Wimpy=75, Normal=100, Rough=125; does not influence player damage, only damage against the player
 * DT_armor - armor Damage Threshold
 * weap_pen - 5 - if weapon has Weapon Penetrate perk, 1 - otherwise
 * armor_pierc - armor piercing critical hit; 5 if it happens, 1 - otherwise; does not apply to Damage Threshold if the weapon already has the Weapon Penetrate perk
 * DR_armor - armor Damage Resistance
 * DR_ammo - ammo Damage Resistance modifier

Critical hit armor-piercing effect
An armor-piercing critical hit effect divides both DT and DR by 5 and (where applicable) rounding the result down. Weapons that already have the Weapon Penetrate perk do not gain an additional DT-reducing effect.

A weapon's ammunition DR modifier is factored in after the armor-piercing critical effect. This means that if the ammunition has a sufficiently negative DR modifier, an armor-piercing critical will negate 100% of the target's DR. Conversely, if the ammunition's DR modifier is poor (a large positive number), then DR will reduce a considerable percentage of even an "armor-piercing" critical hit's damage.

The positive DR modifier caused by the trait Finesse is nullified by the armor-piercing critical effect.