Armor Class
About
- Armor Class (AC) is displayed in 'score' as well as served by MSDP.
- AC is a negative value. The more negative the better.
- AC is primarily consulted in relation to melee attacks
Historical Basis in D&D
- Armor Class in SMAUG 1.8 is based on older D&D editions that used the "To Hit Armor Class 0" (THAC0) approach.
- Realms source code has variables for "thac_00" and "thac_32" specially, so while I am sure the exact implementation differs, the premise of the system is likely similar.
- See: https://dungeonsdragons.fandom.com/wiki/THAC0
- I'm not going to reverse engineer how this works mechanically, the point is it's like D&D so make some assumptions.
Item AC vs. Player AC vs. Affects AC vs. Mob AC
- Item AC:
- Each item has it's own AC, displayed in 'identify' output as: "Armor class is ## of ##."
- This number defines how many hits the item can take before it scraps.
- Repairing the item resets this back to its max.
- Acid attacks may 'etch' the equipment, reducing its max AC. Not repairable.
- Each item has it's own AC, displayed in 'identify' output as: "Armor class is ## of ##."
- Player AC:
- The sum of all your Item AC's. Except not really, there's one caveat:
- The calculation depends on the wearable location of the item. Some are summed, some are negated, some receive a multiplier. (see below)
- The sum of all your Item AC's. Except not really, there's one caveat:
- Affects AC:
- Some items also have "Affects AC by -##" as one of their attributes
- This number is added to your Player AC
- Mob AC:
- A mob has its own inherent 'naked' AC (think of this as their skin)
- A mob may be wearing equipment that increases AC (just like players wearing equipment)
Mechanics
- Melee attacks compare Hitroll against AC to determine if a melee attack hits/misses.
- It is believed that 1 HR of attack equals 10AC of defense. (10 hr vs. 100 ac would be a tie)
I'm not reallllllly going to dig into this. But, let's just make up a super simple example that miiiiiight be how it works?
Let's just call HR 'hit' and AC 'defend', and ignore the negative value of ac, and divide AC by 10 since 1 hr = 10ac:
Player: 100 hit, 100 defend (-1000 ac) Mob: 99 hit, 50 defend (-500 ac)
So, if we hit for "100", we're going to succeed, because the mob can only defend "50" really.
If the mob hits for "99", they're going to miss, because we can defend "100" (we have "1" or actually 10ac to spare)
I think in short that's the spirit of things, and it's probably sufficient to leave it there for a rudimentary understanding of how AC/HR work together.
Dodge/Parry Factors
Just for clarity, wanted to also mention that Dodge/Parry type stuff can also obfuscate HR/AC outcomes:
- The Hitroll happens first and if it doesn't beat AC then the damage value is set to 0.
- Buttttttt Parry/Dodge/etc are still processed. If they succeed, the text changes to that relevant 'you parry' messaging, etc.
- If Parry/Dodge fail, then the text "your attack misses" is displayed
Thus, a HR/AC "miss" can end up being displayed as a Parry/Dodge
Old Code vs. Current Code
One major caveat here is that it is known that historically, Mob AC was limited to a max -300 (So 30 HR would always 'hit')
Newer SMAUG code however can set Mob AC to -1000, things are different now. (So 100 HR to always 'hit')
Due to the old limitation however many 'old mobs' still use those low values, so player HR had/has to be kept toward low values, or we would nearly always hit. This is why 'old gear' (especially old clan eq) tends to have equal values of DR and HR on it, whereas newer gear typically has DR, but little, no, or negative HR. They're combating HR creep to deal with this old/new ac values issue.
Additionally, many mobs simply have other 'workarounds' coded to ensure melee damage misses most of the time (immunities, progs, probably other programmatic solutions)
Lowbie Display
Until level 25, a player does not know their exact AC, instead only seeing a brief description based on the value as seen in the table below:
| AC | Description |
|---|---|
| -201 and lower | that of an avatar |
| -101 to -200 | the envy of emperors |
| -81 to -100 | the envy of dukes |
| -61 to -80 | the envy of barons |
| -41 to -60 | the envy of knights |
| -21 to -40 | excellently crafted |
| -11 to -20 | the envy of squires |
| -1 to -10 | well crafted |
| +9 to 0 | moderately crafted |
| +19 to +10 | that of a knave |
| +39 to +20 | scant protection |
| +54 to +40 | of poor quality |
| +79 to +55 | shabby and threadbare |
| +100 to +80 | improper for adventure |
| +101 and higher | the rags of a beggar |
Slot Multiplier
From 'help ac' we are told that where a piece of equipment is worn also impacts its functional Armor Class:
"Items worn on extremities or wielded will not have any effect on the wearer's AC" "Key locations (Body, Legs, Head) will multiply the item's AC by 2 or 3"
| Worn Location | Multiplier | Example Item AC | Example Applied AC |
|---|---|---|---|
| Finger | - | 10 | 10 |
| Neck | - | 10 | 10 |
| Body | x 3 | 10 | 30 |
| Head | x 2 | 10 | 20 |
| Legs | x 2 | 10 | 20 |
| About | x 2 | 10 | 20 |
| Waist | 10 | 10 | |
| Wrist | 10 | 10 | |
| Shield | 10 | 10 | |
| Hold | 10 | 10 | |
| Weapon | x 0 | 10 | 0 |
| Ear | x 0 | 10 | 0 |
| Eye | 10 | 10 | |
| Back | 10 | 10 | |
| Face | 10 | 10 | |
| Ankle | 10 | 10 |