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Armour class: The nitty-gritty

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  • mf2112mf2112 Member, Moderator Posts: 1,919
    I started up a new character with the same class and stats as your charname and I didn't have it. Do you have any mods installed?
    Alonso
  • AlonsoAlonso Member Posts: 806
    Nope. None at all. I also started a new game and didn't see the -2 vs. missiles either. Just in case, I used the same class, race, stats and proficiencies, and still no -2 anywhere. I guess this might be a minor bug that was present with the version I had when I started the game (v2.0, I think), but has been fixed since then. It's probably better to just leave it. I just used my newly acquired eekeepering ability to correct the game.

    Thank you for helping :)
    mf2112
  • The user and all related content has been deleted.
    jackjack
  • AlonsoAlonso Member Posts: 806
    edited July 2016

    Why do you want things like the Ring to be shown separately??

    I don't. I was just using it as an example of what is a modifier. I just wrote a couple of examples off the top of my head of the correct use of the words "modifier" and "bonus". But they're just examples, I don't really know if they would fit the game. It's a complex issue, and it would require some detailed analysis.

    "AC: 2"

    is a much much more efficient way of communicating what needs to be communicated (your effective base AC is 2 against all damage types) [...]

    I don't know what "effective base AC" means. I've searched "effective base" in the three manuals of the game, but they don't include that expression. Thus, the effective base AC can't really communicate much. You can read the 400 pages of the manuals and still not know what it means.

    Anyway just install my armor mod and you won't have to worry about differences vs. damage types (which are arbitrary and unintuitive).

    Since this is effectively my first playthrough (I played the game some 13 years ago, but I don't remember much), I'm reluctant to installing mods, but, just in case, what does your mod do?
  • semiticgoddesssemiticgoddess Member Posts: 14,903
    @Alonso: "Base AC" is a character's AC without any modifiers at all. Normally, it's 10.

    Wearing armor, or using magical bracers or casting certain spells, sets your base AC to something lower. Wearing chain mail sets your base AC to 5, so it's basically a bonus 5 to AC.

    However, unlike most AC modifiers, base AC doesn't stack with itself. Plate Mail, the Barkskin Spell, the Ghost Armor spell, and the Bracers of Defense AC 8 will all improve your AC. But if you use all of them on the same character, only the strongest one will have any impact, which in this case is Ghost Armor. So you don't need to put magical bracers on the guy in full plate mail.

    Base AC is just a kind of AC bonus that doesn't stack.
    jackjack
  • AlonsoAlonso Member Posts: 806
    The term "base AC" (which I guess means something different than "effective base AC") does appear in the manual in a few occasions, but it is never explained. Again, if it is as basic as its name suggests, I would expect the concept to be explained somewhere in the 400 pages of manuals.

    "Base AC" is a character's AC without any modifiers at all.
    [...]
    Base AC is just a kind of AC bonus that doesn't stack.

    If both things are correct, it means that a character's AC without any modifiers at all is just a kind of AC bonus that doesn't stack. Doesn't make much sense to me.
  • semiticgoddesssemiticgoddess Member Posts: 14,903
    @Alonso: I'm not following you. Base AC just means normal AC, the number you start out with.
  • FinneousPJFinneousPJ Member Posts: 6,455
    This guy... :D
    jackjack
  • [Deleted User][Deleted User] Posts: 0
    edited July 2016
    The user and all related content has been deleted.
    Post edited by [Deleted User] on
    FinneousPJ
  • AlonsoAlonso Member Posts: 806
    edited July 2016
    Thank you, Julius. The mischieves of the dynamic duo have been reported again. I hope they take your advice and this is the last time I report anybody.

    @Alonso: I'm not following you. Base AC just means normal AC, the number you start out with.

    I'm trying to understand the meaning of "base AC", in part because it looks like it could clarify the issue with the Modifiers section. In order to do so, I was trying to highlight the problem I saw in your explanation. Let's approach it in a different way. I'll give you my educated guess of the meaning of "base AC" and you tell me if I got it right:

    Base AC: The AC a character has when he's not wearing any items or affected by any magical effects which provide AC bonuses that stack.

    Alternative version: The AC a character has when any items he's wearing or magical effects that affect him which alter AC do so by setting the AC to a certain value, as opposed to altering it by a certain amount.

    Longer version:
    The AC a character has when he meets one or more of these conditions:
    • He's naked.
    • He's wearing an armour, or AC enhancing bracelets, or an AC enhancing tunic.
    • He's under a magic effect which sets his AC to a certain value, like the spell Ghost Armor.
    AND he meets all of these conditions:
    • He's NOT wearing a shield
    • He's NOT wearing an AC enhancing ring, necklace, cloak, belt or helmet.
    • He's NOT under a magic effect which alters the AC by a certain amount, like Enhanced Harmony.
    Is any of these (or hopefully all of them) correct?

    I've been racking my brains for quite a while to figure out these definitions, and I am not even sure they are correct... So it's not a simple concept at all. It deserves a full thread (or several) on its own.
  • JarrakulJarrakul Member Posts: 2,029
    Not really, no. The base AC is the character's armor class before conditional bonuses and penalties are applied. Most things that adjust AC adjust base AC. For example, if you put on a Ring of Protection +1, your base AC improves (lessens) by 1 point. This is the value that the game displays as your armor class.

    However, when you're actually attacked, the game doesn't (generally) check against your base AC. It checks against your base AC plus conditional bonuses and penalties, depending on the attack. These are the modifiers listed on the character sheet. To return to our earlier example, if a character in plate mail has a base AC of 3, they may also have a conditional bonus of -3 vs. slashing. That means that if the character is attacked by a slashing weapon, the attack will check against an AC of 0, rather than the base value of 3. If there are no relevant conditional modifiers, the attack will check against the character's base AC.

    In general, it looks like this:
    Base AC + appropriate conditional bonuses/penalties = AC actually used in the attack

    And for what it's worth, the conditional bonuses and penalties are collectively known as "modifiers" because that's the only relevant term that doesn't imply that the change is either good or bad for the character.

    Does that help?
    mf2112
  • kjeronkjeron Member Posts: 2,367
    edited July 2016
    Base AC:
    The default, unmodified value is 10 (for Player Characters, at least).
    It is the only Armor Class that can be "set" to a specific value, and is the only type of Armor Class that does not stack, you receive the best(lowest) value among all sources.
    Armor, Bracer's of Defense, Archmage Robes, Barkskin, and the Armor Spells modify your Base AC.
    Depending on the game/version, it may also represents the Monks level-based Armor Class.
    This information is location in the Red Box as:
    Name of Source (if available)
    Armor Class: Value
    Generic AC Modifiers:
    This includes any Armor Class modifier that affects Armor Class against all weapon types.
    Such sources include: Dexterity, Shields, Rings/Amulets/Cloaks of Protection, Magical Helmets/Boots, Weapons of Defense, etc...
    Depending on the game/version, it may also represents the Monks level-based Armor Class.
    All these modifiers are cumulative.
    All these modifiers get listed separately, and include their source name if possible, or just "Bonus" otherwise. This information is presented in the Blue Boxes as:
    Name of Source: Value of Modifier(-Bonus, +Penalty)
    Total AC:
    This is the cumulative total of Base AC and Generic AC Modifiers.
    This is what the "Armor Class Modifiers" section modifies.
    It is presented in the White Box. The "Modifiers" section next to it is a redundant reposting of the following section (I honestly do not know why they added it, but it was just added in v2.2 I think.)

    Specific AC Modifiers: (Crushing, Slashing, Piercing, and Missile)
    These are what are labeled as "Armor Class Modifiers" in the Inventory/Record Screen breakdown.
    There are 2 main types of sources:
    - Belts and Adventurer's/Traveler's/Knave's Robes, these provide a simple bonus to one of the four types.
    - Shields and Armor, these use specific Armor Class bonus's and penalties to "match" the Armor Class values in their description. Examples:

    A buckler reads:
    Armor Class +1
    No protection against Missile or Piercing attacks.
    So it has 3 Armor Class Effects:
    +1(bonus) Generic Armor Class
    -1(penalty) Piercing Armor Class
    -1(penalty) Missile Armor Class

    A Plate Mail reads:
    Armor Class: 3 (0 vs. Slashing)
    So it has 2 Armor Class Effects:
    Set Base Armor Class: 3
    +3(bonus) Slashing Armor Class

    A Chain Mail reads:
    Armor Class: 5 (3 vs Slashing, 7 vs Crushing)
    So it has 3 Armor Class Effects:
    Set Base Armor Class: 5
    +2(bonus) Slashing Armor Class
    -2(penalty) Crushing Armor Class
    These are displayed cumulatively by Armor Class Subtype, they are not separated by source. This information is presented in the Green Boxes as:
     Armor Subtype: Value of Modifier(-Bonus, +Penalty)

    mf2112semiticgoddessAlonsoGrond0
  • jackjackjackjack Member Posts: 3,251
    Ugh, we're reporting people for explaining things now? I knew that button was a mistake. This stuff has always been pretty straightforward to me. Sorry it's so confusing, but others have explained it better than I can.
    FinneousPJ
  • JarrakulJarrakul Member Posts: 2,029
    I don't think anyone's been reported for explaining things. I think people have been reported for making fun of the person asking the question. Whether you think that's reasonable or not, it seems like an important distinction.
    Alonso
  • Mr2150Mr2150 Member Posts: 1,170
    edited July 2016
    It does modify your AC but it is a conditional modification.

    Having two sections, one called modifiers and one called bonuses would make no sense unless you had a third section called penalties, and I'd argue that all bonuses/penalties (whether conditional or otherwise) were modifiers.

    Your AC is modified by 3 under certain conditions. Your AC receives a bonus of 3 under certain conditions. Your AC receives a penalty of 3 under certain conditions. All work perfectly fine. HOWEVER, as seen... not all modifiers are bonuses, some are penalties. Modifier is an acceptable umbrella term.

    What's lacking is consistency of +/- on the modifier ...
    Post edited by Mr2150 on
    Jarrakul
  • jackjackjackjack Member Posts: 3,251
    Jarrakul said:

    I don't think anyone's been reported for explaining things. I think people have been reported for making fun of the person asking the question. Whether you think that's reasonable or not, it seems like an important distinction.

    Fair enough, though I still think that feature is a terrible idea.
  • semiticgoddesssemiticgoddess Member Posts: 14,903
    @Alonso: You've got it. Mechanically, it's just a form of AC that doesn't stack.
  • AlonsoAlonso Member Posts: 806
    Thank you for the answers. Looks like we have two opinions here:
    Jarrakul said:

    if you put on a Ring of Protection +1, your base AC improves (lessens) by 1 point.

    The bonuses of rings stack, so according to @Jarrakul, the base AC includes bonuses and penalties that stack.

    it's just a form of AC that doesn't stack.

    kjeron said:

    Base AC: [...] is the only type of Armor Class that does not stack

    According to @semiticgod and @kjeron, the base AC doesn't include bonuses and penalties that stack.

    Do you think we can clarify this?
  • semiticgoddesssemiticgoddess Member Posts: 14,903
    @Alonso: Base AC doesn't stack with itself; it still stacks with other bonuses. Example:

    Bracers of Defense AC 8 and Leather Armor both grant base AC 8. Equip them both, and they don't stack.

    Blur and Defensive Harmony both grant normal AC bonuses. Cast them both, and they stack.

    A Potion of Crushing and the Girdle of Bluntness both grant AC bonuses vs. crushing. They stack with each other.

    Put all of them on a character with no other bonuses and its AC will go from 10 to:
    8 (leather armor)
    to
    8 (the bracers don't do anything)
    to
    5 (Blur)
    to
    3 (Defensive Harmony)
    ...for most weapons. But for crushing damage, the AC will be:
    -1 (girdle)
    to
    -11 (potion)

    The important thing to know is that the following things don't stack with each other (though they will stack with anything else):
    1. Polymorph base AC
    2. All forms of armor, plus robes of the archmagi and Vecna
    3. Potions of Defense and Potions of Invulnerability
    4. The following spells: Barkskin, Shield, Armor, Ghost Armor, Spirit Armor
    5. All bracers of defense
    6. The Shield Amulet

    Everything stacks except for those things.
    mf2112Alonso
  • JarrakulJarrakul Member Posts: 2,029
    I fear I may have accidentally added to the confusion. Let me try and clarify.

    AC comes from three types of sources: things that set AC to a certain value (what semiticgod is referring to), things that add to or subtract from AC (rings of protection, very high or very low Dexterity scores, etc.), and things that add to or subtract from AC only against specific damage types (some magical items, side effects from most types of armor). We'll call these types 1, 2, and 3 respectively.

    What semiticgod is referring to as base AC is the best type 1 value the character has (they don't stack, so only the best one applies). What I was referring to as base AC is the sum of your best type 1 value and all applicable type 2 modifiers. I'm not actually sure which is the correct definition, but it doesn't really matter as long as you understand how AC is computed, which is the following:

    [best type 1 value that the character has] + [all type 2 modifiers that the character has] + [all type 3 modifiers that the character has against that this particular type of attack] = [final AC used for the attack]

    So yeah, sorry if I confused things. Hopefully that clears things up a bit?
    Grond0Alonso
  • DeeDee Member Posts: 10,447
    Your Base AC is the number to which all modifiers are applied.

    Your AC is calculated as the following formula:

    Base AC + Modifiers

    An item like Plate Mail, which sets your AC to a specific value, is setting your character's Base AC.

    An item like a Small Shield, which applies a bonus to your AC, is applying a modifier. Dexterity also applies a modifier.

    In the case of the Small Shield, it's also applying a conditional modifier if the attack against you is dealing missile damage.

    When a mechanic in the game is referring to your Base AC, it's only talking about the number that is set by a suit of armor. Otherwise, it's referring to your AC, which is to say the total of your Base AC plus all applicable modifiers.

    An armor's description in the Adventurer's Guide lists, for each damage type, the aggregate total of the armor's Base AC and the conditional modifier for that damage type. It's not strictly accurate to the game's internal mechanics, but it's close enough to give a player the information they need to understand their character's abilities. The nuance of difference isn't significant enough to alter your strategies, in any case.

    I hope that helps.
    Mr2150semiticgoddessjackjackAlonso
  • semiticgoddesssemiticgoddess Member Posts: 14,903
    @Dee: A Small Shield technically doesn't add a conditional modifier that excludes missile damage. It adds a normal AC bonus, but then imposes an AC penalty vs. missile damage.
  • DeeDee Member Posts: 10,447

    @Dee: A Small Shield technically doesn't add a conditional modifier that excludes missile damage. It adds a normal AC bonus, but then imposes an AC penalty vs. missile damage.

    Right. But that's the internal mechanic, not the concept (a small shield provides no benefit against missile attacks).
    semiticgoddessAlonso
  • AlonsoAlonso Member Posts: 806
    edited July 2016
    Note: For the sake of the discussion, I will skip the issue of the correct use of the word "modifier" for now.
    Dee said:

    When a mechanic in the game is referring to your Base AC, it's only talking about the number that is set by a suit of armor.

    I guess you mean it's talking about the number that is set by one of the items listed by semiticgod:

    the following things don't stack with each other (though they will stack with anything else):
    1. Polymorph base AC
    2. All forms of armor, plus robes of the archmagi and Vecna
    3. Potions of Defense and Potions of Invulnerability
    4. The following spells: Barkskin, Shield, Armor, Ghost Armor, Spirit Armor
    5. All bracers of defense
    6. The Shield Amulet

    Edited (mistaken): In this list, by the way. the Shield amulet does stack with the others, at least a few of them.
    Dee said:

    An item like a Small Shield, which applies a bonus to your AC, is applying a modifier. Dexterity also applies a modifier.

    This means that the Modifiers section only lists conditional modifiers and leaves out the rest, which is quite misleading (I think that has caused a significant part of the confusion in this thread).
    Post edited by Alonso on
  • joluvjoluv Member Posts: 2,137
    Alonso said:

    In this list, by the way. the Shield amulet does stack with the others, at least a few of them.

    Really? Which ones?
    Alonso
  • AlonsoAlonso Member Posts: 806
    edited July 2016
    Edited (mistaken): I have seen it stack with The Robe of Vecna, bracers of defence and Ghost Armor. I'm almost sure it stacks with the others as well.
    Post edited by Alonso on
  • semiticgoddesssemiticgoddess Member Posts: 14,903
    @Alonso: I assume you saw your AC decrease upon casting Ghost Armor, but it did not stack; it merely overrode the others, due to being the lower value, at AC 2. Or wearing Bracers of Defense AC 3, which would override the Robe of Vecna but not Ghost Armor. Unless you have some mod that tweaks them.
    jackjackjoluvJuliusBorisovAlonso
  • AlonsoAlonso Member Posts: 806
    Ooops, sorry, my bad. For whatever reason I mixed up the Shield amulet with the Protector +1.
    semiticgoddess
  • DeeDee Member Posts: 10,447
    edited July 2016
    Alonso said:

    Note: For the sake of the discussion, I will skip the issue of the correct use of the word "modifier" for now.

    Dee said:

    When a mechanic in the game is referring to your Base AC, it's only talking about the number that is set by a suit of armor.

    I guess you mean it's talking about the number that is set by one of the items listed by semiticgod
    Yes, that's correct.
    Alonso said:

    Dee said:

    An item like a Small Shield, which applies a bonus to your AC, is applying a modifier. Dexterity also applies a modifier.

    This means that the Modifiers section only lists conditional modifiers and leaves out the rest, which is quite misleading (I think that has caused a significant part of the confusion in this thread).
    That's also correct. Your AC score is the total of your Base AC and any modifiers that do not have conditions (like a Small Shield's +1 AC bonus). The modifiers section lists the modifiers for specific damage types. It doesn't list other modifiers because those are a part of your total AC score.
    Alonso
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