MAngband

While to-damage is very easy to understand (+5 does 5 more damage.  That's it.)  I've not found an explanation of to-hit.  I searched RGRA w/ google groups, but I found several conflicting articles about what influences critical hits, and how.  I really don't have much idea how much to-hit helps my hitting.. or my critical hits.  Any of you skilled code-readers have any info?

Sure thing, I'll get back to you later.

Critical hits are mainly a function of weapon weight.

This is specific to MAngband 0.7.2a, and may be different for some variants. It should be 100% accurate for vanilla MAngband 0.7.2 unless Crimson changed it since he released the source. This is especially invalid for OAngband or any other combat-altered variant! You'll need basic algebra skills to figure this sorta-spoiler out... that having been said, on to the document.

(this information can be found by a search for to_h in cmd1.c and cmd2.c)

Melee Weapon To-Hit:
Variable 'bonus' = player to-hit + weapon to-hit.
Variable 'chance' = player fighting skill + (bonus * 3)
(3 is the base to-hit addition. The game defines this as BTH_PLUS_ADJ in defines.h.)

5% chance to automatically hit,
5% chance to automatically miss,
if variable 'chance' is < 0, miss,
if target is invisible, chance = chance / 2
if chance < (target AC + target to-A if target is a player) * 3/4, miss,
otherwise hit and apply weapon critical hit code.

Melee Weapon Critical Hits:

Variable I: (weight*10) + ((player to-hit + weapon to-hit) * 5) + (player level * 3)

If a random integer 0-5000 is <= I then:
Variable K: (weight*10) + random integer 0-650
if K < 400, "good" hit ((2x dmg) + 5), done.
if K < 700, "great" hit ((2x dmg) + 10), done.
if K < 900, "superb" hit ((3x dmg) + 15), done.
if K < 1300, "*GREAT*" hit ((3x dmg) + 20), done.
otherwise '*SUPERB*' hit (( (7/2)x dmg) + 25), done.

To get a superb hit, you need a weapon that weighs at least 5.0 lbs.
To get a *GREAT* hit, you need a weapon that weighs at least 25.0 lbs.
To get a *SUPERB* hit, you need a weapon that weighs at least 65.0 lbs.

Ammo to-hit:
Variable 'bonus': Player to-hit + ammo to-hit + launcher to-hit
Variable 'chance': (Player ranged skill + (bonus * 3)) - distance travelled
(3 is the base to-hit addition. The game defines this as BTH_PLUS_ADJ in defines.h.)

5% chance to automatically hit,
5% chance to automatically miss,
if variable 'chance' is < 0, miss,
if target is invisible, chance = chance / 2
if chance < (target AC + target to-A if target is a player) * 3/4, miss,
otherwise hit and apply ammo critical hit code.

Ammo Critical Hits:

Variable I: (weight*10) + ((player to-hit + launcher to-hit + item to-hit) * 4) + (player level * 2)

If a random integer 0-5000 is <= I then:
Variable K: (weight*10) + random integer 0-500
if K < 500, "good" hit ((2x dmg) + 5), done.
if K < 1000, "great" hit ((2x dmg) + 10), done.
otherwise, "superb" hit ((3x dmg) + 15), done.

By the sources, you need 50 lb units of ammo to get a great hit, and 100 lb ammos to get a superb hit. That's really weird, until you consider that this is used for thrown items as well.

Thrown item to-hit:
This is pretty much the same as ammo to-hit, except no launcher bonuses are applied, and instead of ranged skill, it applies throwing skill - which is hidden from the player, but it's basically the same as your base race/class/level shooting skill. See that part.

[hr]

Currently the heaviest artifact weapon in the game is Grond, at 100 lbs, and the heaviest non-artifact weapon is a Mace of Disruption, at 40 lbs.

The weapons capable of *GREAT* hits out of the box are: Lochaber Axe (25.0 lbs), Scythe (25.0 lbs), Scythe of Slicing (25.0 lbs) Executioner's Sword (26.0 lbs), Two-Handed Flail (28.0 lbs), Lance (30.0 lbs), and Mace of Disruption (40.0 lbs). That is the entire list.

Items capable of great hits: Large wooden chest, Small steel chest, Large iron chest, Large steel chest. The large steel chest is the only thing you can throw that will get a superb hit. That is the entire list.

Artifact melee weapons capable of *GREAT* hits: Zarcuthra, Mormegil, Crisdurian, Eorlingas, Mundwine, Trident of Wrath, Avavir, Grond, Thunderfist, Deathwreaker. That is the entire list.

Grond is the only weapon in the game capable of *SUPERB* hits, which it should get just about every time.

Artifact armor cabable of great hits when thrown: Razorback, Bladeturner.

As far as I know, this is the only complete documentation on weapon, ammo, and thrown to-hit. Enjoy!
- Berendol -

Ok.. the critical hit part makes absolute sense.  However..
Assuming player to-hit of 40 and weapon to-hit of 10

Legendary + (50*3) = Chance

That doesn't make much sense....
I did a search through the codefiles for the word Heroic, a weapon skill level, and got this.

/*
* Returns a "rating" of x depending on y
*/
static cptr likert(int x, int y)
{
     /* Paranoia */
     if (y <= 0) y = 1;

     /* Negative values */
     if (x < 0)
     {
           likert_color = TERM_RED;
           return ("Very Bad");
     }

     /* Analyze the value */
     switch ((x / y))
     {
           case 0:
           case 1:
           {
                 likert_color = TERM_RED;
                 return ("Bad");
           }
           case 2:
           {
                 likert_color = TERM_RED;
                 return ("Poor");
           }
           case 3:
           case 4:
           {
                 likert_color = TERM_YELLOW;
                 return ("Fair");
           }
           case 5:
           {
                 likert_color = TERM_YELLOW;
                 return ("Good");
           }
           case 6:
           {
                 likert_color = TERM_YELLOW;
                 return ("Very Good");
           }
           case 7:
           case 8:
           {
                 likert_color = TERM_L_GREEN;
                 return ("Excellent");
           }
           case 9:
           case 10:
           case 11:
           case 12:
           case 13:
           {
                 likert_color = TERM_L_GREEN;
                 return ("Superb");
           }
           case 14:
           case 15:
           case 16:
           case 17:
           {
                 likert_color = TERM_L_GREEN;
                 return ("Heroic");
           }
           default:
           {
                 likert_color = TERM_L_GREEN;
                 return ("Legendary");
           }
     }
}

Can't quite figure out how to get a number for each skill level from that..

(Edit)  Reviewing this.. I just got an idea.. does say
Case:7 and 8 under very good mean that very good = 7-8?  But there's no "case" under heroic and legendary..
would that mean 17 is the maximum player skill bonus?

You're very close. It's a standard C switch block. The 'case' statements precede what happens if those cases are met - so 7 and 8 return Excellent. You'll notice the 'default' one. That executes if none of the cases are met, which happens when (x/y) > 17.

Here's the short of it:

0, 1: Bad
2: Poor
3, 4: Fair
5: Good
6: Very Good
7, 8: Excellent
9, 10, 11, 12, 13: Superb
14, 15, 16, 17: Heroic
18+: Legendary

Note that no values less than 0 are used. That returns "Very Bad."

Ok.. this confuses me
There's nothing random here besides a flat 5% chance of a direct hit or miss, as I see it.  If you have more (Tohit*3 + fighting skill) then enemy ac (enemy ac * .75)
then you hit.  Otherwise, you miss.. but I don't see that in gameplay...  against something with alot of ac, when I have a low to-hit value i'll have maybe half my hits score.  Wouldn't it either be 19/20 score or 19/20 miss on average?

It's not all that random, really. This is *all* of the math behind it, and you might just get an unusual sequence of random numbers once in awhile.

This has some interesting gameplay implications...
So once you get past a certain to-hit + skill value, you'll be able to hit morgoth 19/20 of the time.  Before that, you'll hit him about 1/20 of the time?
Thanks a lot for all the info!