Basics of Combat, Volume 3, Parry

So yesterday we took a quick look at the math behind the To Hit chance for melee combat. Now we are going to take a look at how the target's chance at parry chance is calculated.

Both dodge and parry allow the target to completely avoid the damage from an incoming attack, even though that attack counts as a hit. Both parry and dodge used the same formula, but some of the numbers are different. In the case of the parry skill, Strength is more important, and in the case of the dodge skill, Dexterity is the key attribute. Keep in mind that both of these skills do make use of both attributes and both of these skills are directly opposed by you opponents offense skill. We will touch on the target's Dodge chance next posting.

Let's start with the Parry skill, since it comes first on the To Hit roll tree. Like all skills, parry gains a bonus from the Strength attribute equal to 1.75 times the value. Now you also get a bonus to your parry skill equal to your Dexterity skill divided by 12. Then all of the various bonuses for items and abilities are then added. Let's take another look at our first level warrior.

Remember that he hasn't had a chance to increase any of his skills and he has an 18 in his Strength attribute. Unfortunately, the cost for having a high Strength is a lower figure in most other attributes and our little warrior friend only has a 14 Dexterity score. This means this stats are as follows:

Parry Skill - 1
Parry Bonus - 0
Strength Bonus - 31.5
Dexterity Bonus - 1.2

So to figure out the Warriors total parry skill, it would be as follows:

(1 / 5) + 31.5

Or, in other words, the total parry skill would be 31.7. The Dexterity bonus will come in later.

In order to determine our warrior's parry chance we now need to determine how is opposed by the attacker's offense skill. Queue the Goblin!

Ok, so the goblin is, as previously mentioned, a MOB (Monster OBject) and therefore has a skill value equal to its effective level (1) times ten, so this Offense skill is 10. Offense is equally dependent on two attributes, both Dexterity and Strength. So it gains a bonus equal to the average of these two scores. Now our little goblin isn't the strongest nor the most agile of the species, as such, his Strength is a 16 and his Dexterity is 14. Goblins also don't gain any racial bonuses to Offense (aside from their smell) nor is he lucky enough to have any magical items. So his stats are as follows:

Offense Skill - 10
Offense Bonus - 0
Strength and Dexterity bonus - 26.25

So the goblin's total Offense score would be:

(10 / 5) + 26.25

Or, in the end, the total of 28.25.

Now let's throw these numbers into the following formula to determine the warriors chance to parry an attack from the Scar-Eyed Goblin:

Parry Chance = 5 + Target's Dexterity Bonus + (Target's Parry Skill - Attacker's Offense Skill)

So the values would be:

5 + 1.2 + (31.7 - 28.25)

5 + 1.2 + 3.45

So the final parry chance would be 9.65, since the NWN2 engine truncates all fractions, the final parry chance would be 9%. Since value is over the minimum parry chance of 3%, we keep it instead. :D

So even if the goblin hit the warrior, it would still have 9% chance to avoid any damage.

Again, for those of you who enjoy the quick numbers:

1) For every 5 skill points in your chance to parry is modified either up or down by 1%.
2) For every Strength point your chance to parry is modified either up or down by 1.75%.
3) For every Dexterity point your chance to parry is modified either up or down by 0.08%.

Next time we will take a look at a target's dodge chance. Until then, see you in the game!