Combat Determination in 3.2

[Tregonsee]

Not being a developer, I would like to know more about how melee combat is determined in Vanilla 3.2. Is there an easy formula or series of formulas for this?

I mean I know when I am playing D&D, I know my base chances to hit vs. various monsters and what factors affect my success and to what degree, but I don't for Angband

[Derakon]

Originally Posted by Tregonsee

Not being a developer, I would like to know more about how melee combat is determined in Vanilla 3.2. Is there an easy formula or series of formulas for this?

Ha ha ha, no.

The combat mechanics are almost gleefully obscure, particularly things like critical hits and monster chance to stun you. I recommend just sticking with the numbers that you get from monster recall (after killing enough of a monster to get its AC) and 'I'nspecting your weapon.

[Tregonsee]

That is what I meant. I want to be able to determine base chance to hit against monster X if I know my plusses to hit with a given weapon and their AC.

Does level and or class come into play, or is that already calculated in my Character Description?

[Ycombinator]

Combat formulas in Angband are not something you want to calculate with pen and paper, indeed. But let me try to summarize them. I assume version 3.2.0 (I haven't familiarized myself with nightlies yet).

The following applies to player's attacks vs monsters. Monsters do things in a different way.

1) There is always a 5% chance to miss and a 5% chance to hit (like natural 1 and natural 20 in D&D). Auto-hit, however, does not mean a critical hit.

2) Attack roll is 0..(N-1) vs 3*AC/4, where N is determined as follows:

N = skill + 3 * to_hit_bonus.

N is halved if target is invisible.

For ranged attacks, distance in tiles is subtracted.

Skill is determined only by character's class, race, and level (think of base attack bonus in D&D). There are separate skills for melee fighting, shooting, and throwing things. In-game character screen gives you only vague descriptions instead of actual numbers. To give you a sense of scale, "Very Bad" is below zero, "Poor" is 24..35, and "Legendary" is 216 or more.

To-hit bonus is a sum of character's inherent to-hit bonus and equipment bonuses. Inherent bonus is determined by both STR and DEX, which contribute equally. It is universal for all attacks, melee and ranged.

Monster's AC is determined solely by monster's type. Again, to give you a sense of scale, AC of a small kobold is 16 and Morgoth has AC 150. Thick hide of Tarrasque provides it with whopping AC 185.

3) Damage is calculated as follows: weapon's base dice are rolled, the best of available slays or brands multiplier is applied, then weapon to-damage bonus is added, then critical hit modifier is applied, and finally off-weapon to-damage bonus is applied.

Note that slays and brands work best with big dice weapons.

4) Your chance to land a critical blow is determined by the weapon weight (bigger is better), total to-hit bonus and character level:

critical_chance = (weight + to_hit * 5 + level * 3) in 5000.

Weight is in 1/10 lbs.

If a critical hit is scored, the second roll is made to determine how *awesome* it was. Only weapon weight affects its results. Here is a little table for melee attacks:

it was a ... hit    damage formula  min. w. required, lbs   max. possible w., lbs

good                2 * D + 5       none                    40
great               2 * D + 10      none                    70  
superb              3 * D + 15      5                       90
*GREAT*             3 * D + 20      25                      130
*SUPERB*            7 * D / 2 + 25  65                      none

That's why heavy weapons do so much more damage on average (Grond being an extreme example) than a straightforward calculation may show. In-game description already takes that into account.

5) Calculation of blows uses complex tables, but thankfully the game provides you with detailed information about stats required for the next extra blow.

[Tregonsee]

OK, I understood some, but not all of that last post

Originally Posted by Ycombinator

2) Attack roll is 0..(N-1) vs 3*AC/4, where N is determined as follows:

I understand part of that. I assume a couple of things and please correct
me where I am wrong-

Combat is either a 1-20 or a percentile system
You compare your combat value versus the AC of the monster


But what is 0..?

Do you divide (N-1) by 3*AC/4?

Originally Posted by Ycombinator

N = skill + 3 * to_hit_bonus.

N is halved if target is invisible.

So N is my skill at Fighting or Shooting and add three times my to_hit_bonus.
Since I am Level 50 and have maxed stats, I assume this will not change, with the exception of new artifacts.
Is my to_hit_bonus the number given in Character Info under Melee (+xx,+xx)?
If you can see visible, is N still halved?

Originally Posted by Ycombinator

Note that slays and brands work best with big dice weapons.

Do slays and brands affect ability to hit those monsters affected by those slays or brands?

[Ycombinator]

Originally Posted by Tregonsee

But what is 0..?

Uniform distribution of integer values from 0 to N - 1. Like dN - 1. This roll is compared to 3*AC/4.

Originally Posted by Tregonsee

Is my to_hit_bonus the number given in Character Info under Melee (+xx,+xx)?

Yes, it's the first number.

Originally Posted by Tregonsee

If you can see visible, is N still halved?

No. I think, "not perceptible by the player" is a better expression.

Originally Posted by Tregonsee

Do slays and brands affect ability to hit those monsters affected by those slays or brands?

No.

[Tregonsee]

Originally Posted by Ycombinator

Uniform distribution of integer values from 0 to N - 1. Like dN - 1. This roll is compared to 3*AC/4.

OK, I have forgotten most of Calc II. Remind me what "Uniform distribution of integer values" is.

When you compare that to "3*AC/4", are you saying if it is greater, then you have achieved a hit? Is the same as "AC * .75"?

[camlost]

Roll an N sided dice, subtract one. If this number is greater than three-quarters of the monster AC, it is a hit.

[Tregonsee]

When you "look" at a weapon, does it follow that calculation to compute avg. points per round of damage? Does the calculation take into account if you have enchanted a weapon beyond how it was found?

[d_m]

Originally Posted by Tregonsee

When you "look" at a weapon, does it follow that calculation to compute avg. points per round of damage? Does the calculation take into account if you have enchanted a weapon beyond how it was found?

Yes it does.