Armor Class – How Hard is it to Hit and Damage Something?

[Herremann the Wise]

Armor Class – How Hard is it to Hit and Damage Something?

As a theoretical exercise, I’d like to pin down some abstract armor class ideas – non-system orientated but most likely with a D&D angle as that is what I have had the most exposure to.

I’m just pondering the following comments on this thread in regards to shields and heavy armour and how hard it is to hit and damage something.

The problem is D&D's level of abstraction. If shield & armour were considered separately (shield gives cover, armour reduces damage) you'd get a much more realistic effect.

What factors make it easier or more difficult to hit and damage a sword and shield wielding, armor wearing opponent? I suppose the thing to do is to separate the process: how hard is it to effectively hit someone and how hard is it having hit effectively then damaging them? All this while still keeping things abstract to a degree– no separate hit locations.

I’m just going to ramble some things I have in my head. If anything looks or sounds silly, please say so and please feel free to add or subtract.

PART ONE - HITTING

- How quick and dextrous they are? What effect does armor have on this dextrousness? Should it provide a limit a la third edition, or should it be a standard dexterity penalty?

- Armor seems to protect in two different ways, depending upon how the armor wearer is being attacked.
o Against an attacker favouring power over precision, it seems like it should be acting as damage reduction, where a standard amount of damage is subtracted to give the damage that got through.
o Against an attacker favouring precision over power, it seems like it is acting as a “chinkability?” factor. How difficult is it to exploit the chinks in a suit of armor? Does this then allow them to ignore the DR of the armor?

- There seems to be three states for a defender:
o Inert: they are not reacting to the threat of being hit
o Mobile: they are actively trying to avoid being hit
o Dangerous: they are actively trying to avoid being hit and they are actively threatening the attacker at the same time.
How can armor class actively reflect these states? Am I ignoring any states here?

- Having a weapon thus seems to hold a dual defensive purpose:
o It can be used to deflect incoming blows (sometimes and depending)
o It is a threat in itself, making an attacker more wary of not leaving themselves open to instant and deadly retaliation.
How should threatening with a weapon affect AC? How effective is this against multiple opponents? I assume such defences would be useless against ranged weapons, making a defender easier to hit at range than in melee. Ranged weaponry really should be more deadly I think.

- What effect should wielding a shield have? Does it make you more difficult to hit effectively? Is there much difference between using a shield passively and using it actively and with skill? How can an armor class system account for this? How good are shields against ranged attacks?

- How many armor classes are required to interestingly but abstractly portrait the various issues above? Do the following make sense?
o Touch AC
o Flat-footed AC
o Ranged AC (Kind of a base AC, reflecting the mobile state above)
o Melee AC (Reflecting the danger and difficulty of getting into hand to hand with a defender in the dangerous state above)

Anyway, I’ve had lots of ideas floating around in my head, I’d love to read some additional ideas and input on the subject of armor class.

EDIT BELOW

PART TWO - DAMAGE
Just adding the second part of my question in terms of damage.

At present with 3e and 4e, the damage system seems to be fairly standardized into damage + attribute modifier. The only thing to differentiate using a dagger against a greatsword or battleaxe is the random d4, 2d6 or 1d8. Is this reflective of the situation or should an additional weapon loading be added?

For example, if an axe hits effectively should it have a larger weapon bonus to damage reflecting its damage dealing capacity compared to lets say a quarterstaff? For example, a fighter might deal 1d6+2 damage with a quarterstaff but the exact same fighter deals 1d8+5 with a battleaxe? Obviously, this assumes that armor as damage reduction is being used, so the majority of the quarterstaff damage will be soaked up by the armor of the defender whereas the battleaxe has that extra weapon loading to assist in breaching the armor's DR. Does the weapon loading of damage provide a suitable relationship between weapon used and armor attacked?

As a sidenote, I think a similar relationship should exist with the weapon used and the attack modifier to hit an opponent's AC. I find the proficiency bonus of 4e (providing a bonus on your attack modifier) very interesting but completely under-utilized. For example, a club is very easy for anyone to use effectively and so should receive a healthy bonus on the attack modifier [+3 for example]. A rapier on the other hand requires considerable skill in comparison. You might have someone unfamiliar with it cop a nasty penalty [-4], someone proficient with it might just break even [+0] whereas only a fighter specialized in its use gets the bonus [+3] for example.

Anyway just some thoughts between the relationship between the weapon used and hitting or the weapons used and the damage done versus an armor's DR.

I suppose the other related part of this is damage itself and how it relates to hit points. For every edition, D&D has combined two separate things into one:
- Physical damage
- Other factors such as the skill in turning a serious strike into a glancing blow, inner strength, divine favor or even luck.
I think it makes sense to split these two things into their respective corners:
- Hit points: representing physical damage
- Combat points: representing all the other factors but as well, the ability to perform particular maneuvers and skills.

The following was something I wrote a month ago but hey, tell me what you think as it applies to the concerns of damage in an encounter.

HIT POINTS

Hit points now represent the amount of physical damage a character can take before becoming incapacitated or worse. When a character loses hit points, this represents them taking a physical injury. When a character’s hit points reach zero or below, they have taken a serious and possibly life-threatening injury. When a character’s hit points reach their racial death limit or below (for humans it is -10), then they die.
Hit points do not change very much over the life and experience of a character. A character’s capacity for handling physical damage does not change that dramatically. Race as well as a character’s strength and constitution are the dominant factors. Character’s that must regularly handle physically damage also have more hit points than those that don’t.

If a character receives damage that takes them to zero hit points or below, then the character takes a serious injury such as a broken leg, blinding, the loss of a limb or possibly unconsciousness or death. The DM determines the injury and any resulting condition for the character.

If a character’s hit points reach their racial death limit, then the character dies. However, death is not always instantaneous. Sometimes a character can take several minutes to die, where unfortunately nothing can be done except to ease their pain; healing - magical or otherwise - does not work on a character on or below their death limit.

COMBAT POINTS
Combat points represent a variety of facets in combat. They represent how skilled a character is in avoiding serious injury, turning a life-threatening strike into a glancing blow. Sometimes, characters are just lucky or have a level of divine favor on their side. A portion of the number of combat points represents this too. Other characters have deep reserves of inner power, or have incredible physical or mental endurance to keep going, to be able to perform at one’s peak even when under pressure or injured. The greater a character’s ability to survive and succeed in combat, the more combat points they are likely to have.

However, combat points also represent a character’s ability to perform special or heroic manoeuvres, such as tumbling through a group of enemies untouched, cleaving from one foe into another or casting a difficult spell whilst surrounded by enemy swords. Players may spend a character’s combat points so that the character may perform these extraordinary actions in combat.

COMBAT AND HIT POINTS IN ACTION
When a character is struck in combat, the threat and the damage it could cause is subtracted from a character’s combat points first rather than their hit points. This represents the skill a character displays in avoiding serious damage that would normally affect their hit points. Alternatively, perhaps it was a character’s luck or even a deity watching over them assisting in avoiding the full impact of an incoming blow.
For example, imagine a character with a wildly swung axe being flung at their head. With a number of combat points up the sleeve, the character skilfully avoids the seriousness of the blow, the axe bouncing off of the character’s armor rather than severing head from neck; a certain number of combat points being subtracted in the process. The blow is still going to sting but after the battle, it is nothing a bandage and a kiss won’t fix.

Combat points act as a buffer and shield to a character’s hit points, but there are several times when a character’s hit points will be threatened instead with damage being directly applied to a character’s hit point tally.

HIT POINT LOSS
• If a character takes a critical hit, then the resulting damage is subtracted from both their combat points and their hit points. A critical hit represents physical damage being taken by the character.
• If a character is reduced to or has zero combat points, then any further blows will be subtracted directly from their hit points. Zero combat points represent a character being spent, exhausted or injured to the point where they can no longer reliably defend themselves.
• If a character takes damage that cannot reasonably be avoided by skill or luck, then this damage is directly applied. For example, an unimpeded fall from height would be directly applied – a serious hazard for both low and high level characters.

CRITICAL HITS
A critical hit represents an attack that seriously threatens a character. The damage from a critical hit is subtracted from both a character’s hit point tally and combat point tally

Determining a critical hit is similar to third edition whereby the skill of the attacker and the type of weapon used are a factor in successfully performing a critical hit. The Critical Range of a weapon represents the numbers whereby as long as a hit is successful against a target, a critical hit may have been made. A Confirmation Roll is then made. If this confirmation attack is a successful hit against the target, it means that a critical hit has been made.

HEALING HIT POINTS AND RESTORING COMBAT POINTS
The healing of hit points and the restoring of combat points happen at different rates. Hit points are slowly recovered naturally. It can take many days to many weeks to naturally heal the severest of wounds and injuries. The restoring of combat points on the other hand is relatively fast. A character might need a short rest to clear the wits or a slightly longer rest to be back to one’s best in terms of combat points.

The aim is for the system to allow continuity in a game whereby there is a lessened reliance on a character devoted to healing such as Clerics prior to fourth edition and on healing wands and potions. Characters may continue on adventuring, knowing that their combat points will be quickly restored, allowing them to fight effectively, even if carrying a minor wound (a small amount of hit point damage).

In doing so, the game neatly stratifies the health of the characters, so that players can have their character’s behave in a heroic but realistic manner. There are several points aside from unconsciousness whereby characters can react to the danger present, changing tactics to suit the level of threat.

For example, a character with almost full combat points and hit points is going to be going hard and going strong, trying their hardest to have an immediate impact upon the encounter. A player whose character is at low combat points is going to be much more wary, knowing that they are just a blow away from having their hit points totally exposed to the enemy.

A character who has taken hit point damage is also going to be cautious, knowing that another critical hit could cause serious injury or even death. It is hard to imagine characters enjoying such injuries and so players will be more inclined to take defensive action if serious hit point damage has been sustained. A player whose character is at zero or negative hit points is going to try everything possible to have their character avoid getting hit and thus sustaining either another long term injury or even death. Long term injuries can be costly in either time and/or specialized healing. Death is obviously the ultimate cost to the player and hopefully something that can be avoided if players take on board the various health cues available and suitable tactics based upon this. Combat should be more involved than the repeated whittling of hit points until unconsciousness of previous editions. Allow combat to be heroic but also somewhat realistic at the same time.

Best Regards
Herremann the Wise

 

[vagabundo]

My own custom 3.X:

- Amour is now removed from AC - the name AC is kept for BC - but is essentially touch AC
- Armour works as Damage Reduction as per rules from SRD
- HP are replaced with what I termed combat points and are an abstract resource that the player spends to avoid injury if an attack has beaten their AC, actually connected in some fashion with the PC.
- I introduced Wounds, once Combat points where exhausted or if a PC was unable to defend themselves, any damage was recorded minus the amours Damage Reduction, so amour is actually saving your life at this point. Once your number of wounds equals your con score your dead. Up until then you get a penalty on all rolls equal to the number of wounds you have received.
- I had a whole other set of rules for shields, allowing them to provide protection, intercept attacks and larger shields provided better protection from missiles.

I wanted a system that eliminated some of the oddities of AC and keep as much compatibility as possible. I haven't looked at it in a long time, 4e has taken me in other directions.

 

[GlaziusF]

Really, if you're looking for sim, Armor Class is not the place to go for it.

I think of Armor Class as a conversion: an underlying simulation of attack types versus armor types with tons of chained and situational modifiers that spits out a damage "spectrum", into a binary-hit-and-miss model with a fixed damage expression.

For what it's worth, the most exhaustive model I've encountered used a weapon-vs-armor matrix and a shield bonus depending on size, then added a variable bonus from weapon and shield depending on stance, called everything below a certain threshhold "misses", fed the result through a penetration matrix to determine damage and critical rank, then tacked on a critical if appropriate. Armor and shields could be enchanted for straight defense bonuses (common) or "padded" to reduce the damage and critical rank of incoming blows.

 

[Switchblade]

Your first pt.
Armour on dex. It does make a difference but not neccesarily dirrectly. Most "dodging" is just stepping back out of a swing or a sidestep around a thrust so as long as the legs are mobile armour wouldn't
make too much difference. I found the first time I fought in mail down to below my knees weighing 1/3 my body weight it didn't impede my footwork as I was just as agile as before. However... I tired a LOT quicker and that slowed me down in the long run. Someone with a bit more strenght and stamina than me (practically everyone) would suffer less. I've never fought in full harness though I guess that would make someone a little less agile.
TBH though while fatigue rules may be more realistic an abstract dex cap is a lot more game friendly. Prehapse cap dex at lower of strenght or stamina with heavy armours instead of a fixed dex cap might be an easy compromise.

Your second point
A mail hauberk with coif covers you head to knees and elbows. With some mail mittens, gauntlets and so on and a great helm you can get near total coverage. (Kiss good bye to peripheral vision though). The heavier armours (harness) tended to be rather comprehensive, go to a musium and look at the plate and just try and find an unarmoured spot. Good luck. They have weaker spots but even they are well armoured and asking someone to hold their arm above their head so you can go for the armpit in a fight is going be tricky. I wouldn't allow an attack to avoid more than 1/2 the DR unless they are able to slip a dirk through the eyeslot of a prone foe. Something like allow coup de grace to ignore DR from armour if using a piercing weapon.

Re states of defender, hitting someone who isn't parrying or stepping back away from your weapon is pathetically easy, you practically have to try to miss.
Inert should be an auto hit, mobile would help but is still very easy to hit. Only when they are fighting back or have something to parry with does landing a blow get tricky and require skill. I think these 3 states cover all eventualities though.

Weapons and AC: I'd say having a weapon and the skill to use it would make up the lions share of the total AC. If you are up against someone who can't strike back and can concentrate entirely on offence hitting
them becomes trivial. Against someone who is weilding a quaterstaff, knows how to use it and is making you keep your guard up they are very difficult. A good example is Ars magica, it has (had? I'm behind editions) the deffense score based on:Weaon skill (where 4 is a good skill and 6 is outstandling)+weapon defense bonus (0 for a dagger up to 6 for a stave)+dex - weight penalties.
Some AC based on your total attack bonus of the weapon you are wielding, with some weapons having defence bonuses/penalties.

Shields: Yup, they make you MASSIVELY harder to hit. Yup, skill does make a difference. Knowing how to brace a shield, when to keep it in against your body or with arm at full extension (the advantage of a centre boss grip over arm straps) and how to keep your guard up while attacking helps get the most out of it. Against range attacks, pretty good, should give same bonus to ranged as melee.

AC types:
Yup, this should cover it.

 

[mmadsen]

If shield & armour were considered separately (shield gives cover, armour reduces damage) you'd get a much more realistic effect.​

I agree with S'mon's point, but a good deal of it comes down to the subtle math of rolling d20 + modifiers against a target number. Stacked bonuses are unusually effective. You might think that each +1 to AC means you get hit 5% less often, but that's simply not true. Going from getting hit on a 19 or 20 to getting hit only on a 20, for instance, halves the number of hits you take; it doubles your expected lifespan in combat.

It turns out that a spear man with little armor gains little from a shield, while a dismounted knight with heavy armor gains a tremendous amount from a shield, which is the opposite of what we'd expect.

- How quick and dextrous they are? What effect does armor have on this dextrousness? Should it provide a limit a la third edition, or should it be a standard dexterity penalty?

Armor has little to no effect on a warrior's ability to block with his shield or parry with his weapon. Its effect on his overall agility is also fairly mild -- but wearing armor is exhausting, as the weight adds up and the heat becomes unbearable. (It's like cutting weight in a sweat suit. Not fun.)

An upper limit on agility bonuses makes much more sense than a simple penalty, because an immobile warrior should suffer no penalty for encumbrance, but an extremely light-on-his-feet warrior should have difficulty staying light on his feet.

- Armor seems to protect in two different ways, depending upon how the armor wearer is being attacked.
o Against an attacker favouring power over precision, it seems like it should be acting as damage reduction, where a standard amount of damage is subtracted to give the damage that got through.
o Against an attacker favouring precision over power, it seems like it is acting as a “chinkability?” factor. How difficult is it to exploit the chinks in a suit of armor? Does this then allow them to ignore the DR of the armor?

Once armor advanced to high-quality plates, it became futile to attack fully armored body parts with an ordinary sword. D&D's armor class mechanics model this fairly well; the challenge is hitting an unarmored (or less-armored) spot.

Heavy thrusting swords (tucks or estocs) were developed for just this purpose; you could jam them into the chinks in the armor and thrust home. Narrow daggers were developed for the same purpose -- but you had to knock the other knight to the ground and pounce on him to use such a small weapon effectively.

The other tactic was to switch to a heavy mace -- which is a surprisingly small weapon, by the way -- to concuss foes, or to an axe, which can overcome armor better than a sword.

So, yes, you can either avoid armor or overcome it.

- There seems to be three states for a defender:
o Inert: they are not reacting to the threat of being hit
o Mobile: they are actively trying to avoid being hit
o Dangerous: they are actively trying to avoid being hit and they are actively threatening the attacker at the same time.
How can armor class actively reflect these states? Am I ignoring any states here?

If every attacker could allocate part of his attack bonus to defense, that would model your combat states fairly well -- except that fully rational players (and GMs) don't freeze up and neglect to fight back, the way demoralized fighters do in real life.

- What effect should wielding a shield have? Does it make you more difficult to hit effectively? Is there much difference between using a shield passively and using it actively and with skill? How can an armor class system account for this? How good are shields against ranged attacks?

Shields are tremendously useful, especially against ranged attacks, which follow a set trajectory from a ways off. Shields are also especially useful in formation, where there's little room to dodge, but each soldier can "borrow" the shield to his right.

 

[xechnao]

o Dangerous: they are actively trying to avoid being hit and they are actively threatening the attacker at the same time.
How can armor class actively reflect these states? Am I ignoring any states here?

This seems to be the most common situation in combat and conventionally our combat system should be developed from this point. D&D's AC is strange to this situation but since D&D is not necessarily perfect we better restructure the combat system starting from the point above.
So lets take this situation for granted: this means that one combatant's efforts are directly in relation with the other combatant. This relation means that we can compare the two combatants and see who is more efficient than the other. The more efficient one will be in advantage and the less efficient one will be at a disadvantage. We can model this in a game by allowing both to roll a dice versus Target Numbers that reflect success levels, one combatant rolling with a bonus the other with a penalty and decide what happens based on the difference of their successes and how these are equipped and how they fight (for example if one equipped with a shield wins with a small difference of success levels this could mean that he can only maintain his shield utility versus another attacker that could threaten him in this round if he wishes so or attack his adversary with some small advantage in the next round).

So instead of the AC and BAB I go you go we have a direct advantage-disadvantage system by comparison that I think seems more realistic.

 

[Altamont Ravenard]

I think the Conan RPG adresses this issue in a way you'll find satisfactory (or at least interesting / inspiring).

Going from memory:
Armors give DR, shields give cover
When defending, you can decide to dodge (using dex, avoiding blows) or parry (using str?, blocking blows)
A Str fighter needs to punch through DR to hurt his opponent
A Dex fighter needs to beat the target's AC (modified by the DR value of the armor) to bypass armor DR completely (so you're basically finding the hole in the armor where to stick your knife in).

AR

 

[Stalker0]

This is the reason you shouldn't have DR with armor.

Dnd tries to model a variety of weapon styles and allow playability, from the dagger wielding guy to the guy wielding the huge plank of metal.

DR hurts the dagger guy more then the plank guy, always has. Armor as AC hinders them both equally.

The game encourages more fantasy archetypes that way, so I'm never too keen on DR ideas for armor in dnd.

 

[mmadsen]

DR hurts the dagger guy more then the plank guy, always has. Armor as AC hinders them both equally.

I think the concept of armor reducing damage makes good sense, but, as you point out, the implementation leaves much to be desired.

Rolling a small damage die for a small weapon -- even before we start subtracting damage because of armor -- already has its problems. After all, a single dagger wound can kill someone, even if multiple dagger wounds still won't guarantee a kill.

Really, you want a system where each attack can disable or kill, but some attacks are much more likely to finish someone, and armor reduces the chance that an attack will be crippling.

 

[Mustrum_Ridcully]

I tend to see 3 "defense options" in combat:
- Parry
- Dodge (or is this just a different narration for a parry, or vice versa?)
- Soak

D&D combines all of them in one number, AC.

I've played a little of Warhammer. It uses Dodge and Parry as defensive options. They only work against one attack. This makes Warhammer very deadly against multiple enemies, and you really want to rely on the Armor and its damage reduction to avoid the worst.

I think how the "don't take any damage at all options" work defines a lot on the deadliness of a system. If you can bring them to bear against every enemy, dodging/parrying/armordeflection is very powerful and enemy numbers matter a lot less.

This creates an interesting dynamical change - if, for example, you can parry only once per round, a 3.x like Combat Expertise effect becomes less interesting the more enemies you fight. If it works against everyone, it gets more desirable the more enemies you fight.

I find this very interesting and I wonder how to balance such a system "fairly" - or if it's even possible (or needed - maybe it's okay if you get extra benefits / less benefit against different number of foes...)