Magic Armor affecting attack rolls vs. modifying target AC

[sepulchre]

Waysoftheearth wrote

A 1 HD man with a -1 HD would have zero effective attacks, so the implication at the Man-to-Man level (or wherever belligerents have 1 HD each) appears to be that magic armor is impervious to normal attack.

I had a feeling this would lend itself to such an implication. It's rather brilliant, have to think on this.

There was a CM magic armor rule which specifically states attackers suffer a -3 adjustment on the Man-to-Man tables if the target has magical armor (roughly equivalent to -6 on a d20). Although this rule is apparently superseded in D&D-land, it might be handy to bear in mind.

More amenable to my purposes, but the elegance of the former is persuasive. Thanks Ways!

[waysoftheearth]

Jun 3, 2015 11:50:27 GMT -5 tetramorph said:

Can someone speak (in a kind way) to the benefit of having magic armor affect attack rolls rather than simply modify the target AC?

Back for round two on this fascinating topic ...

Let's assume we have a plate armored fighter (AC 3) with the benefit of a Protection from Evil spell.
Let's also assume that this spell implies that evil attacks are 2 chances in 20 less likely to hit the fighter.


Okay, so the question is whether we should:

A. Adjust the fighter's AC by 2 pips (to AC 1) and leave the attacker's throw unmodified, OR
B. Leave the fighter's AC unmodified (AC 3) and adjust the attacker's throw by -2.

Aside from the few edge cases (discussed above) these will produce the same chance of a hit or miss, so it's no big deal either way.


Now let's introduce any kind of attack which bypasses either armor or magical protection, but not both. Some such attacks might include: partially-ethereal monsters or weapons, light sabres, anti-magical monsters or weapons, perhaps even firearms (CHAINMAIL says regardless of the armor classification of their target, Arquibusiers will kill any figure they hit). Will it matter what armor a man is wearing when a catapult stone crushes him? Or a ballista bolt skewers him? When a ghost passes through him? When a net is cast over him? When an Evil High Priest merely needs to touch him? And so on.


So let's look at A and B again for when armor doesn't count:

A. The fighter's (magically adjusted) AC is 1, and the attacker's throw is unmodified.
Now if we ignore the fighter's armor, dropping him back to AC 9, he will loose his magical protection too. That's not entirely fair to the fighter; so to give him his proper due we will have to "reverse engineer" the part of his AC due to armor (that can be ignored) and the part of his AC due to magical protection (which can't be ignored), in order to conclude that he should--for the purpose of this specific attack--be treated as AC 7. We might need to figure this out for each figure for each attack, on the fly as it's happening in combat. It's doable, but it's awkward. It could easily slow the game as we mess with the variables, particularly if there are several of them or they are changing turn by turn (e.g., spells beginning or ending, magic shields coming into play, potions drunk, etc).

B. We left the fighter's AC as is (AC 3 for plate armor) and adjusted the attacker's throw by -2.
Now if we ignore the fighter's armor, he is simply dropped back to AC 9. The attacker's throw is still adjusted by -2. Game continues with no particular no fuss. Yes, we potentially still need to track all those things that might be changing over time, but this is effectively what the attack adjustment figure is: a placeholder to remember the sum of all those non-armor attack adjustments.


Clearly it can work both ways... just thought this scenario lends itself to separating out armor from attack adjustments. 


FWIW, in my game I've played about with a house rule whereby heavy crossbows disregard armor (i.e., treat all targets as AC 9), and two-handed swords, poleaxes and the like treat all man-sized targets as AC 6. The latter means heavy weapons are better at cracking heavy armor, but worse at hitting light/nimble targets, which is a kinda interesting trade-off for players. As it happens, it also brings the above into play.


Hope that's helpful

[tetramorph]

waysoftheearth, wow that is some serious hypothetical situation thinking!

I think, for me, such a situation would come up so rarely in one of my games that I would be willing to sacrifice the difficulty of figuring it out in the moment for the simplicity that AC adjustment allows me 9/10s of the time.

But I do get your logic here.

I also use Delta's "Target 20" for attack rolls: d20 + HD + target AC >/= 20 indicates successful hit.

With such a simple, addition-based calculus makes judging these outliers just about equally simple. That is to say, adjusting target AC vs. adjusting magical affects or attack-penalties all comes out in the wash when you are adding a d20 roll plus (whatever) AC (applies) the HD of the attacker and subtracting any necessary temporary spell or condition.

Fight on!

[waysoftheearth]

Jun 14, 2016 10:37:39 GMT -5 tetramorph said:

that is some serious hypothetical situation thinking!

It's not entirely hypothetical ... the main reason I got to thinking about all this is because it comes up in my game with heavy crossbows and two-handed weapons.

Jun 14, 2016 10:37:39 GMT -5 tetramorph said:

I also use Delta's "Target 20" for attack rolls: d20 + HD + target AC >/= 20 indicates successful hit.

With such a simple, addition-based calculus makes judging these outliers just about equally simple. That is to say, adjusting target AC vs. adjusting magical affects or attack-penalties all comes out in the wash when you are adding a d20 roll plus (whatever) AC (applies) the HD of the attacker and subtracting any necessary temporary spell or condition.

Sure. I used to swear by Delta's Target20 method too, but I've kinda done that now and reverted to the tables for a couple of reasons:

1. Yes, d20 + HD "works" generically across the board. But it's also more granular that D&D's attack tiers for player-types so you tend to "lose" any sense of D&D's distinction between normal scumbags and Heroes and SUPERHeroes.

2. Target20 requires you to do math on every throw, while comparing a die to a table does not. Despite being a bit of an advocate for Target20 myself, I've found the latter is usually quicker for me in real life.

3. Tables can present information that is not easily presented in formulas (e.g., see the MtM and FCT matrices, and even AD&D's alternative matrices). A formula wants smooth consistency, but it's the anomalies that are uniquely D&D. I have a sense that the smoothing formulae are each "taking something" out of the game, leaving us with something that is smoother, but less unique.


In any event, the Target20 formula doesn't separate "attack adjustments" from "AC", so it has the same issue for any case where you want to ignore armor. It could be done like this:

d20 + HD + target AC - attack adj. >/= 20


Or, if you want to stick purely to addition, like this:

d20 + HD + target AC >/= 20 + attack adj.



Another side of it is; if you want to frig about with the Man-to-Man attack matrix it almost becomes necessary to separate attack adjusts from armor type, or--if not--accept that sometimes magical protection will just do nothing. E.g., an attacker with a mace requires a throw of 8+ to hit a man with no armor, leather armor, or mail armor. So adjusting the target's AC will have no effect, while adjusting his attack dice will have an effect.


Yet another reason (probably the top one for me, in fact) is just to try it out because it's different to what you're used to and see how it flies

[waysoftheearth]

Digging up this old thread...

It occurred to me recently (during play) that a useful side-effect of adjusting attack rolls behind the scenes is that the player need not get a free insight that this is "plate mail +2" or whatever it happens to be. If that's your thing.

E.g.
Player: I put of the plate armor.
Ref: Okay, your AC is now one.
Player: Cool; it must be plate +2 guys.

versus
Player: I put of the plate armor.
Ref: Okay, your AC is now three. (Secretly notes opponents will attack at -2).
Player: Hmm... should we use our Detect Magic yet, or keep it 'til later?


Of course, the ref could make a secret note that the player's AC is 1 instead of 3. But in that case the player then has incorrect information rather than just missing information, and his true AC now obscures his armor type.

[Deleted]

Or you can do it the way we did it 45 years ago, and

Player: I put on the plate armor
Ref: Okay, you're wearing plate armor.

Don't TELL the players what their *$&^ING armor class is. Stop thinking in rules and think in natural language!

[waysoftheearth]

It was a naive example to illustrate a point.

I agree your suggestion (minus the profanity) can work great. I'd add that it can also be pragmatic to have the players track their own details. A lot of players favor character sheets designed specifically for this kind of thing. Sure, the 1975-76 sheets don't have a space specifically for "AC", but I'm guessing a lot of players would want to jot it down anyway.

Telling them they are now wearing plate, full stop, implies ac 3 to anyone who has a passing knowledge of the rules. So you're basically suggesting don't give players meta detail, which I agree is a good idea. The discussion was, I believe, more about what the ref does behind the scenes, so I probably shouldn't have brought players into it.

[captaincrumbcake]

I didn't go back and read this entire thread so, not sure if I've already added anything to the mix. But...


1. It seems to me as if this enigma should have been answered in an early Dragon magazine Q&A; if not earlier in a SR. Here's what the actual text of Vol.2 says:

ARMOR: Armor proper subtracts its bonus from the hit dice of the opponents of its wearer. If the shield's bonus is greater than that of the armor there is a one-third chance that the blow will be caught by the shield, thus giving the additional subtraction.

I'm sure Gronan, and Rob and others from the time can deposit commentary regarding how this ruling was played by them, with their DM. And one can, of course, embrace whatever interpretation of this mechanic was utilized by them or anyone else. Or, you can interpret it for yourself and come to your own conclusion.

I agree with a previous comment that the "subtracts its bonus from the hit dice of the opponents of its wearer" was supposed to mean, from the attack roll of the wearer's opponents. Thus, if a 4 HD monster was attacking a fighter with +2 chain mail and +3 shield, the creature would need to roll a natural 11 or better, but with the armor bonus of +2, the creature would have to roll a 13 instead, as 13 - 2 = 11. However, one in every 3 attacks would actually require a roll of 16 or better, since the shield's bonus is considered in addition to the armor; 16-5 = 11. One could simply add the bonuses to the base number required to hit AC4, and the result would be the same. 

But that's how I read it.

[aldarron]

Aug 27, 2015 8:47:16 GMT -5 sepulchre said:

Perilous, how have you handled movement rates in the 6 second melee rd? Have you just divided the turn rate by 10? This distinction has been pivotal in addressing charging vs. missile fire in our scenarios.

So really that's fodder for another thread. but the short answer is you don't.  Movement rules are for the movement phase.  In melee combat, per CHAINMAIL, you can engage any opponent within 30', infiltration and Fighting Capability rules permitting.  Attempt to leave the combat zone, and retreat rules apply.   

[sepulchre]

Aldarron wrote:

So really that's fodder for another thread.

Agreed, admins feel free to move this elsewhere. Perhaps, Aldarron and I can make this a quick exchange.

The short answer is you don't. Movement rules are for the movement phase. In melee combat, per CHAINMAIL, you can engage any opponent within 30', infiltration and Fighting Capability rules permitting.

Agreed. Yet, historical re-enactment shows trained archers loosing an arrow every 6-8 seconds.  This rate of fire overlaps with the melee round should one read the round as discrete and quantifiable (a subject of debate in OD&D Forum threads).  

Movement rate for a figure being harried by an archer would be operative should it wish to survive the turn. 

Finding the movement rate per round by dividing the [charge/flee rate/turn] would yield how many rounds are required to close the distance between the figure and the archer and how many arrows the figure must suffer before engaging him.   

Admittedly, one could dispense with dividing the movement rate and rule all arrows spent in the turn itself are considered a 'volley'.

Necropraxis describes this as a ranged attacker choosing to expend more missiles in exchange for +1 'to hit' or damage and a 1in6 chance the quiver is exhausted by the end of the turn.  
www.necropraxis.com/2012/09/16/abstracting-missiles/

My House rule:
A "volley" is really another name for the many missiles an archer or slinger expends in a turn.
A volley loosed upon 1 target raises the chance to hit by 1. 
A volley loosed upon multiple figures grants an 'unmodified' attack dice/target (maximum of 6).
A volley yields 2in6/turn one's quiver is exhausted.

[aldarron]

Great points Sepulchre, but as I play it at least, there's still no need to break down movement this way.

No argument on the realistic rate of fire. I can loose and re-nock in a matter of seconds myself - albeit my accuracy suffers. Sticking BTB, an archer will have two shots per turn in CM. Toss in the 1/2 turn "move" of OD&D and that's one shot per move.

So lets say an orc is in a hallway 50' away, and charges a PC archer. The archer gets one shot at the orc because the orc can cover the distance in the time/space of 1 move. Never mind how many fps an orc can travel and never mind how many seconds are supposed to be in a move. These things are abstracted.

If the orc were only 30'away then the archer and the orc are already in Melee range, and thus in rounds not moves, so it is a matter of initiative. If the PC is faster they could shoot once before the orc closes the distance to engage (like in surprise in the OD&D FaQ). If they orc has the initiative it will once again close the distance and be too close to shoot at.

In my own games I allow an exception to the above if the archers are shielded in a second or third rank behind other players but still within melee range. They can shoot into the melee every round - so yeah every 6 seconds. I think that idea of being able to shoot from the second rank, so to speak is along the lines of how Mike Mornard describes OD&D combat and makes sense to me. (Not too mention no player likes to be told they have to sit out a combat round due to some obnoxious rule)

[sepulchre]

aldarron wrote:

No argument on the realistic rate of fire. I can loose and re-nock in a matter of seconds myself - albeit my accuracy suffers

Had no idea you plied a bow, how fantastic!

The archer gets one shot at the orc because the orc can cover the distance in the time/space of 1 move. Never mind how many fps an orc can travel and never mind how many seconds are supposed to be in a move. These things are abstracted.

Well said, "move(s)" and a die roll 'to hit", rather than fiddling with rounds and the movement rate.  The number of moves rather than movement/melee round would be the measure of how many attack dice are in play, e.g. two moves yields two rolls of 2d6 'to hit'.

...already in Melee range, and thus in rounds not moves...a matter of initiative 

Again 'these things are abstracted'. Great point. Categorically, closing/charging in Melee range is different from closing/charging movement rate/turn. 

...an exception:shielded in a second or third rank behind other players but still within melee range. They can shoot into the melee every round - so yeah every 6 seconds... along the lines of how Mike Mornard describes OD&D combat and makes sense to me.

Yes, this follows.

(Not too mention no player likes to be told they have to sit out a combat round due to some obnoxious rule)

Ha! For sure.