Blunt resistance, Cut resistance, Cut resistance efficiency (previously Stun), Harpoon resistance, and Coverage are statistics on pieces of armour that affect how much Damage a unit takes from another unit's attack.
Coverage is simply the chance that armour will protect against a hit to that limb. So a 100% chest coverage will apply its resistances on every hit to the chest. While a 50% coverage will only do it half the time. Meaning that 80% coverage does not translate to covering 80% of the Damage Taken calculated for this hit, but that for 20% of hits the armour will offer no protection.
In the case of overlapping coverage areas, damage resistance is determined based on the slot the items use. It will run through them in order of: Head, Armor (Chest), Pants, Shirt, and then Boots. Environmental resistances are a sum total.
Whenever an attack successfully hits a unit, the damage is theoretically calculated as follows:
AD: Attack damage / "Raw damage"
BR/CR : Blunt/Cut resistance / "Armour effect"
DR: Damage resistance / "Toughness effect"
Damage taken = AD * (1 - CR/BR) * (1 - DR)
For example, say a 100 Blunt Damage attack is going to hit your character's chest (not blocked) while they are wearing a Standard Grade Plate Jacket, which has 14% blunt resistance. Your unit has a toughness of 70, which gives a 26% (0.26x damage resistance). So, our final number would look like this:
100 * (1 - 0.14) * (1 - 0.26) = 100 * 0.86 * 0.74 = 63.64 damage taken
Cut Resistance and Efficiency
Cutting Damage uses the same initial calculation, but triggers a Damage Conversion calculation. All resisted cut damage is then applied against the Cut Resistance efficiency (CRE) statistic to determine how much of the resisted damage is carried over as unmitigated Blunt (previously calculated as Stun) damage.
For example, lets use 75% cut resistance and 60% cut resistance efficiency with no Toughness modifier for simplicity. Your character is hit for 50 cut damage. The armour negates 37.5 damage applying the formula above, sending the remaining 12.5 to be applied to any overlapping armour. The 37.5 resisted cut damage goes through the following (Stun) calculation:
(Stun) Damage = Resisted Cut Damage * (1 - CRE) = 37.5 * (1 - 0.60) = 37.5 * 0.4 = 15 damage
This (Stun) damage will be converted to blunt and instantly applied (ignoring any other armour). This means that if you had no other armour you took a total of 27.5 damage, 12.5 cut and 15 blunt. Keep in mind though, this (Stun) damage ignores further layers of armour. So you may want to avoid armour with a low Cut resistance efficiency value in slots that get hit early on in the order.
Also, there are other factors to consider for damage calculation, as Shidan explains in this thread (outdated):
This is simply the amount of damage points negated when hit by a harpoon or crossbow on a body part this armour covers. Normal coverage rules still apply.
Penalties and Bonuses
Most armours have penalties to certain skills. These are shown a 0.67x or something similar. This means that skill will only function at that percentage of your skill level. So a 50 skill would only function at 33.5 using the previous number as an example. If you have multiple penalties across all your armour all the factors are multiplied, e.g. two equipped items with a 0.9x: 1 - (0.9*0.9) = 1-0.81 = 19% penalty. The maximum penalty is 95%. Some penalties are reduced at higher qualities.
While this stat is for weapons, it is still should be noted as this stat can make a difference. Basically, the % of Armour penetration (AP) of weapon will directly affect the current BR/CR of the armour of their enemy. Ex:
- You are wearing a 50 BR Samurai Armour, the enemy is using a +30% AP Spiked Club
- They initially done 100 blunt damage, but because of the AP bonus, your BR are decreased by 30% into 35.
- Therefore you would only resist 35 blunt damage, and received 65 blunt damage.
Likewise same can be done with penalties
- You are wearing a 90 CR Samurai Armour, the enemy is using a -20% AP Katana
- They initially done 100 cut damage, but because of the AP penalty, your CR are increased by 20% into 108.
- Practically you would receive pretty much no cut damage and resisted all of those 100 cut damage, but...
- However since it is cut damage, blunt damage from efficiency should still be considered which isn't affected by AP stat at all, if the efficiency was 90%, then you would receive 10 blunt damage.