So I'm working on this D&D-ish game (link here in case you wanna check it out but it's not necessary), and we've been playtesting it for awhile now using armor as damage resistance, but seeing as it's a D&Dish game I want to see what D&D fans prefer for whatever reason: armor as damage reduction/resistance or traditional Armor Class (or a kind of hybrid, like in 3E's Unearthed Arcana which had armor give small amounts of DR and AC bonuses).

If you prefer armor-as-DR, what systems do it right for you? How complicated is too complicated? We've only tried using static values with armor piercing, but someone brought up Stormbringer which I guess uses random rolls for DR.

My convoluted thoughts.

Damage reduction has a risk of making weak attacks weaker. DR 4 against a dagger that does 1d4 damage, for example. Minimum damage mitigates this somewhat.
Random DR makes this less of a problem, but makes armor somewhat unreliable. I've used this a bit in Dungeon Crawl Classics for some monsters.
Ablative armor turns armor into another pool of "hit points". More stuff to keep track of, and makes it necessary for characters to make more frequent pit stops for armor repairs.
Staged armor gives armor more staying power than plain ablation, but is even more stuff to keep track of. This is the armor system I use for my homebrew Transformers RPG.
(This is the Stopping Power armor system of Cyberpunk 2020.)

For D&D, I tend to get fed up and just use the traditional armor as damage avoidance, with a smattering of DR for especially tough foes, or as a feature of some magical armors versus specific damage types.

Armor as DR every time but also armor as HP.  Really, the core Palladium system is pretty good.

Both have advantages and disadvantages, so a mix might well be best.

Your game is very close to Dragon Age/Fantasy Age. They use Armor as reduction, shields add to Defense. What happens is your hit points go and up and down like a yo-yo. Character parties use magic, talents, and the heal action to keep hit points totals up. If it crashes down too far that when things start to fall apart. Effective combat means dealing damage faster than than the other side can heal the target. In this respect Fantasy Age is similar to how D&D 4e works. D&D 5e has a little of this but it not as pronounced.

In contrast in a system like GURPS or Harnmaster it about putting up an active defense. About denying the hits. Once you are hit "bad things" start happening very quickly. These games are noted for death spirals that start after the first good hit. The character gets hit and less effective at defending and unless his party covers for it, he will be at a permanent disadvantage unless he got lucky.

Both general concepts produces systems with quick combats and both produces systems with long combat. What you need to do is start playing, note the stuff that doesn't fit your vison, revise, and playtest again. Do this over and over again as often you can with as many people as you can. Goto local conventions, use Roll20 or Fantasy Grounds and recruit on the internet. Goodman Games did this with the DCC RPG and it is a enduring hit for them. Likewise Paizo took a while with Pathfinder in beta before they started publishing final rulebooks.

AC (what a weird term for defense) is the very reason I dislike everything d20.

Armor as DR, with heavier versions reducing defense. Slower and tougher versus faster and squishy.

I love armor as DR as AC made no sense to me.

Quote from: cranebump;933795Armor as DR, with heavier versions reducing defense. Slower and tougher versus faster and squishy.

I'd disagree with the "reducing defence" part, because not having to care about glancing blows is a very good boost to your defence even if the armour made you less mobile. Which it generally doesn't, what it makes you is easier to tire out;).


Thing is, there's two ways to imagine armour. Keep in mind that historical plate armour (and contemporary fencing helmets:p) don't usually let any force reaching your body, because there's a distance between your body and the armour.

You can imagine armour as "allowing me to absorb some blows that would kill me if I took them unarmoured". That's what it looks like for you, in defence. I've long preferred this method strongly. Today, I still prefer it, but have learned to live with the other far more easily:D!

Or you can think of armour as cover that moves about with your body, and only allows hits in that pass around the armour, via very small, mobile openings, which you have to target while the guy in armour is trying to kill you. The plate cannot be overcome by most cuts, and even with "armour-piercing" weapons, you have to deliver a high-power attack on a moving opponent, on an area where the plate is weak or weakened. Even a small misjudgement might mean your strike was wasted and slides off instead of tearing through, as the enemy "rolls with the blade", despite the blow being by a blade (which generally doesn't allow "rolling with it").
That's how it looks when you're thinking about your offence against the enemy's armour.

As I said above, I still prefer the DR option, but I can at least imagine how both approaches would translate to;). And I find that "armour as reduction and cover at once" probably works best.

The only Armor as DR that worked for me was Stormbringer where armor stopped a random amount of damage as per an armor die roll. For me, if you are going to slow down the game, you might as well add in the concern that the blade may slip past the less tough part of the armor. AKA, sometimes your battle axe chunks into the toughest part of the breastplate (low axe damage vs. high armor roll) and sometimes your dagger slips into a weak groove (high dagger damage vs. low armor roll).

Warhammer is a weird one where your body's Toughness is way more important than your armor.

Otherwise, I don't see what I am getting with DR vs. AC. AC gives me speed of play which TO ME is absolutely key to whether I will enjoy running the game.

I've used DR in OD&D with mixed results. Your shield added to your AC, and half your Armor bonus was your DR. So Leather became +1 AC and 1 DR and Plate was +3 AC and 3 DR. The end result? We played OD&D and it took a longer to resolve combat, even though we were hitting more often. AC 17 (Plate and Shield) became AC 14 with 3 DR so you got hit 15% more often, but 50% of hits did no damage.

But clearly DR is popular with many players.

If you want some sort of quasi-realism, the answer should be 'both'. The only game that does this as a core part of its armor rules is GURPS. You could argue AD&D does it too, because full plate provides damage reduction as well as a good AC (original DMG). But, that's more of an exception that proves the rule. Rolemaster also combines concepts of probability you are hit and amount of damage in its armor treatment, though the mechanics are not very much like AC or DR, and actually armor is sort of an 'anti-AC' in that system (increasing the chance you are struck for modest damage). Anyone who has worked with medieval armors and weapons and done one of the related unrealistic-but-better-than-total-ignorance combat sports can tell you that AC is not at all crazy. Someone wearing plate armor can certainly be hit with an edged weapon, but only in a few spots, along a few specific lines of attack. Most blows from most weapons cannot possibly penetrate plate armor.

Quote from: Snowman0147;933804I love armor as DR as AC made no sense to me.

In Chainmail man to man combat 1 hit = 1 kill. You cross indexed the weapon you were using versus the armor the target was wearing. If you were a Hero you got to roll four times on the table versus normal men. A super hero got to roll eight times.

1 hit = 1 kill was found to be boring so it was expanded to 1 hit doing 1d6 damage and 1 hit to kill was expanded to 1d6 hit points.

Also the original chainmail cross index all the fantasy creatures with each other to generate the to hit number including heroes and super heroes. This was found cumbersome so instead of weapon vs. armor, Gygax decided it was better to have character level versus armor. Later weapon vs. armor was worked back into the game via the Greyhawk supplement as modifiers to the to hit roll. If you play that chart beside the original Chainmail chart you could see the correlations between them.

So what does Armor Class mean? It represents how resistant to damage the target is modified by the attacker's experience (level) and the weapon he is using. An it is an abstraction of a bunch of factor that other games like GURPS choose to detail in their mechanics.

It comes to the same thing, generally.

Average damage is equal to Chance To Hit x (Damage Roll - Damage Reduction)

Put another way, with DR you hit more often but do less damage each time; with AC you hit less often but do more damage each time.

Thus, reducing the damage (DR) vs reducing the frequency of damage (AC) comes to the same thing. The exception was noted by someone earlier, if some weapon's maximum damage is lower than or equal to the DR, then they can hit but do no damage. Maybe you feel it's good a dagger can never hurt someone in platemail, maybe you don't - your design will have to accommodate this.

A second exception is that if you ALSO have ascending Hit Points, then it makes high-DR guys harder to kill than high-AC guys. So you end up with tanks fighting tanks. This is less of an issue is HP stay the same through the game; if a warrior has just 6HP, then whatever his armour someone can always get him, but if he has 50HP, the peasant with the dagger has no chance.

AC is a simpler system.

In D&D I prefer the Armour as AC. To me it represented the factors of trying to find a weak point in the defense and I tend to prefer RPGs where its abstracted like that. Though I do like Star Frontiers armour as extra HP vs certain types of harm.

In my own RPG armour was both. It allowed a chance to deflect a successfull blow. And it absorbed some of the damage dealt if the blow was not deflected.

Armor as Damage Reduction every time.