View Full Version : A new take on Armor Class

2007-08-21, 09:50 AM
So I was thinking, does it make sense that dexterity-born armor class is the same as that granted by actual armor? I mean, it makes sense that they both serve the same purpose: dexterity and armor both help a character to avoid harm, but a very dextrous character dodges out of the way from potentially harmful blows, and a heavily armored one simply allows them to glance off.

I realize that this is the reason Wizards of the Coast came up with touch AC, because a ray of Disintegrate isn't going to stop when it hits a thin sheet of steel. But it seems to me that a dextrous character who is also magically warded, and is wearing armor, has three different levels of protection that an incoming attack must overcome in order.


Borun Ironhand, first-level dwarf fighter, is wearing steel scale mail and wielding a heavy wooden shield, and has a dexterity score of 12. Goblin A attacks him with a shortsword. Using my method, Borun has a touch armor class of 11 (due to his dexterity bonus), and a base armor class of 16 (+4 from the armor, +2 for the shield). The goblin rolls two attack rolls; if the first is less than 12, Borun dodges out of the way, or the goblin misses the dwarf completely, so the shield and armor never come into play. But it the first attack hits, and the second is unsuccessfull, the blade bounces off Borun's armor or shield (maybe even performing a no-AoO sunder in the process). Only if both attacks are successful does the blade cut into dwarf flesh. It also seems that the first attack should be determined by dexterity, as it's an accuracy issue, and the second by strength, as it's a matter of pushing past or cutting through the foe's defenses.

The third and outmost layer of protection (likely with the shield included) would also include magical shields and wards, deflection bonuses and other things, like divine bonuses.


Everything here is completely brainstorm. None of this is tested, analyzed or expected to ever be used in actual gameplay. I'm simply letting out some thoughts and encouraging the rest of you to mind-stirring discussion.

So, what I've got so far is something along the lines of:

Deflective AC:
Deflection bonuses, magical shields, miscellaneous bonuses.
Anything the character doesn't actually have to think about to make function.
Perhaps shields, but my thought of this AC is that it comes into effect without any work by the character, so I'm loathe to add them at present.

Dodge/touch AC:
Dexterity bonus, dodge bonuses, insight bonuses.
When the deflective AC fails, a character has to actually make an effort to protect themselves. They dodge out of the way of a blow or parry it aside.
Shields might also go here, as they are effort-reliant. As you would parry a blow aside with a weapon (which I would call a dexterity bonus), you could also parry with a shield.

Base/core/armor AC:
Armor bonuses and their enhancement bonuses, natural armor.
This is the last armor class. If a blow actually does land on the character, there's still a chance that it's deflected or absorbed by armor, or the natural toughness of the character's skin.
Shields could, of course, also go here. But I'm thinking of this one also as a more unconscious armor. Like deflective AC, it would be present when the character is flatfooted, and wouldn't require effort on the part of the character.


Anyways, that's what I've found so far in my head. I now hand the quill to everyone else. What do you think? Do you like it? Not so much? Would it have any merit at all in an actual game?

Personally, I'm not sure. I don't think I'll likely use it, but it makes for a good discussion.

Another thing: this set of rules makes high-leveled characters even more powerful when compared to low-level characters. When a thenth-level fighter swings a sword at a 1-HD goblin, he has a very good chance of overcoming three ACs of no more than eleven each. But when the goblin attacks the fighter, there is very little chance that it succeeds in three consecutive attacks against fairly high ACs.


2007-08-21, 10:36 AM
Armour Class is an abstraction. If you try to analyse it too closely it will cease to make sense. The categories you have come up with are fairly usual for this sort of thing. Of course, you are not taking into account 'coverage', by which I mean Body Armour does not apply equally to every location, which is why a Mail Shirt in 3e provides less AC than a Mail Hauberk. I don't think it is worth rolling multiple dice to model hit and penetration, nor do I think it would be a better method.

That said, this is how I look at it when seeking to rationalise this abstract concept:

Base Armour Class.
A Prone and Immobilised Character has an Armour Class of 1 (10 - 5 - 4) versus Melee Attacks. Any failure to strike him would not be on account of the target's Skill. 10 + Dexterity Bonus = ability to dodge incoming blows. Any Attack that fails to make contact is a miss.

Shield Bonus
3e D&D tends to treat the Shield as a static defence; the bonus it provides is unrelated to the skill of the combatant. Really, then, it's just a form of cover, granting between +1 and +4 AC. Any blow that misses on account of a shield has been foiled by it.

Armour Bonus
This is the last line of defence. The Character has failed to evade or intercept the incoming attack and now must rely on his Body Armour to save him. A failed attack on account of Body Armour means deflection, absorption, or a combination thereof. A successful (and wounding) attack means the Armour was successfully bypassed, penetrated or failed to absorb the full force of the blow or otherwise negate damage.

This has often led people to seek to introduce a Parrying Mechanic.

2007-08-21, 11:02 AM
That's a lot of rolling. And average BAB will soon exceed these individual, lower sub-AC's, thus making them less effective (unless BAB is adjusted downward).

As the system works now, why not just assume that any attack missing full AC but beating touch AC bounced off one's armor/shield? Does your system improve something, or fix some fatal flaw?

2007-08-21, 11:44 AM
That's a lot of rolling. And average BAB will soon exceed these individual, lower sub-AC's, thus making them less effective (unless BAB is adjusted downward).

As the system works now, why not just assume that any attack missing full AC but beating touch AC bounced off one's armor/shield? Does your system improve something, or fix some fatal flaw?

I agree. the mechanic you showed just means a lot of rolling against lower ACs. In the long run, unless you modified other stuff with it it would probably result in a lot of attacks hitting.

If you want to differentiate between AC granted by armor and dex AC, try the armor as DR (http://www.d20srd.org/srd/variant/adventuring/armorAsDamageReduction.htm) or damage conversion (http://www.d20srd.org/srd/variant/adventuring/damageConversion.htm) variants (I use armor as DR)

Also, a little analysis of your "ACs operate independently" theory. Do you think full plate is more effective if you hold still, or if you try to dodge but you opponent still manages to get a glancing blow?

Let's take that same example character you used and put him in a suit of full plate with no other equipment...

Using normal AC rules...
Under normal circumstances he has AC 19 (10+8 armor +1 dex)
While flat-footed he has AC 18 (10+8 armor)
While holding perfectly still for whatever reason he has AC 13 (10+8 armor -5 dex)

Using the AC rules you showed...
Under normal circumstances he has ACs 11 and 18
While flat-footed he has ACs 10 and 18
While holding perfectly still his ACs are still 5 and 18

Using your rules, his highest AC is 18 regardless. I think it should be easier to shove a dagger in the crack of someone's armor better if they're holding still. the current AC abstraction works pretty well to model this I think. My only complaint is that shields are underrated.

2007-08-21, 01:23 PM
Well...this actually may be salvageable. The issue that seems to be strongly presented is the obscene amount of rolling that this would require; but that is easily fixed. The goblin is only making one attack: therefore there is only one attack roll. If that one attack roll is less than 12, the attack misses completely. If it is greater than 12 but less than 16, the attack hit armor (effects to be determined later) if it is greater than 16, the spear hits soft, tasty dwarven flesh.

I think that may work well with your system.

Maybe if the attack hits armor or shield; said piece of equipment is damaged instead of a character? That could lead to interesting (and possibly frustrating) situations in relation to armor repair.

2007-08-21, 01:56 PM
I much prefer Armour as DR to an AC increase. Afterall, weapons like Greataxes are there for hacking through guys in full plate, they shouldn't have the same effect on armour as a sling bullet or quarterstaff.

2007-08-21, 02:07 PM
Why shouldn't they? Just because a Weapon penetrates Armour (and to be honest a Great Axe doesn't stand that much of a chance versus Plate or a hugely better a chance than a Spear or Sword against Mail) doesn't make it more effective at injuring the wearer than an impact weapon. Armour should probably be a combination of AC and DR, but the implementation will remain abstract regardless.

2007-08-22, 12:44 AM
Interestingly enough, glancing blows and armor repair rarely ever come into play while playing a normal game of DnD... it's a wonder how any armor or weaponsmith makes any money in the game... but yeah, if you did it that way, one attack roll, and have various outcomes depending on the roll, then armor and it's actual use would be something to consider. After all, if you try to sunder an item, such as armor, there's a whole different roll and rules, but you basically don't attack the person, but instead their item... which in the case of Armor is going to get hit either way. Armor as DR is okay, but that means most classes have nothing for AC and natural armor is pretty hefty.