Dodge roll

16 posts / 0 new
Last post
In my party since the release of the 3rd Ed we disliked the feel that static AC gives to us players , and since it is an averaged result by adding the 10 in the formula for determinig AC...;)

Stead of adding the 10 in the formula we roll 1d20 and add the modifiers to avoid each hit:D . The feeling is great! you can almost see your character moving to scape the blow as the die rolls over the table:D .

This is our idea of a perfect change to our game . And we we'll keep using it unless a better option is available;) . Thanks for your input!
I only think a defensive roll would work if there were no automatic hit or miss rules. And if critical hit rules were changed so that instead you needed to hit a certain amount above their defense (however it is calculated).

With 1d20 vs 1d20, you can get a 19 point difference in each direction instead of the usual max of 10.

There is the problem that different weapons crit in different ways, but that is manageable.
You can see that variant written up here.
I only think a defensive roll would work if there were no automatic hit or miss rules. And if critical hit rules were changed so that instead you needed to hit a certain amount above their defense (however it is calculated).

With 1d20 vs 1d20, you can get a 19 point difference in each direction instead of the usual max of 10.

There is the problem that different weapons crit in different ways, but that is manageable.

Also, see the other thread on this page for the same discussion. The problem with rolling d20 vs. d20 is that it makes a 39 point spread between rolls, varying from -19 to +19, totally overwhelming the contribution of skills and modifiers. It is also a different probability distribution than a linear d20 roll.

A better solution is to let the player roll the defense, but have all attackers take 10 on their attack, keeping the variability to a level appropriate for the modifiers (and saving the DM from having to roll so many dice).
The problem with rolling d20 vs. d20 is that it makes a 39 point spread between rolls, varying from -19 to +19, totally overwhelming the contribution of skills and modifiers.

Not really. Look at grapple checks. The modifier still matters plenty. Yeah, maybe the dire bear will roll a 1 and you'll roll a 20. Good luck with that.
The Psionics rules use an opposed roll for the saving throws instead of a fixed value. I'm sure you could do the exact same thing with every roll. I believe that there is an optional rule in D&D that allows players to play with opposed rolls instead of the attacker rolling against a fixed value.

The disadvantage of the opposed roll is that you have to roll an extra dice. I believe that 4E will go away from any opposed roll in order to reduce the amount of dice rolling. You may says that opposed rolls take a minimal amount of time, but they do add up over the corse of the game. It appears that there will be more non-combat checks in 4E as well, so doing opposed rolls there will also take more time.

I think that the opposed roll optional rule will be in 4E. For players who like the dice versus dice feel of combat (or non-combat), you can use it. It doesn't really change the game that much as the math works out more or less the same.
<\ \>tuntman
I understand opposing opposed rolls for the purpose of limiting rolling.

As you say, though, it doesn't make things stupidly random.
Using opposed rolls significantly changes the probability distribution as opposed to one side taking 10 (or 10.5 or 11), biasing it a lot more heavily in favour of the participant with the higher modifier.
Nom- as it should be.

In real combat, the combatant with a superior defense/attack is bound to trump his opponent in the opposite category.

Fight with the SCA, take martial arts, play Amtgard, etc.....you'll see. D&D combat is supposed to simulate combat in a roleplaying game. This provides the best of both worlds- combat and role play. Tactics and social interaction. etc.

If it was all tactics, it's be a tabletop battlegame. If it was all roleplay, it'd be WoD...lol (no offense).:D
I don't know about that.

1d20+19 aways beats DC 20. It doesn't, however, always beat 1d20+10.
Where are you getting the +19 and +10 from, may I ask?

I'm mostly assuming the rules are set up to support an opposed-roll system, not that it's tacked on to current 3.5 rules- which would be a headache.

Base Attack Bonuses and in turn, Base Defense Bonuses, would scale by class. Ability modifiers apply to each, so do various feats/equipment/spells/etc.

Armor no longer provides a bonus to 'defense', instead providing Damage Reduction.

Example:

A 10th level 'Fighter' type with a BAB of +10, has +4 STR mod, a 2-handed weapon that deals 2d6 base damage, and feats (not 3.5) that grant a bonus to Attack- let's say +2, as well as 1/2 his level added to damage rolls, or +5 damage.

Attack = 1d20 + 10 + 4 + 2, and he charges for +2.....

total attack = 1d20 +18 (close to your 19)

His opponent is a 10th level 'Fighter' type (Perhaps an Iron Heroes-esque Armiger type?) with a "Base Defense Bonus" of around +10? He is allowed to add +2 of his Dexterity bonus (if Dodging) to his armor- which provides DR 6 or so. This fighter-type has a higher Strength (+4 mod) than Dexterity, and so chooses to Parry the attack instead of Dodge it....He also has a Shield which grants a +3 bonus to his Defense, and a feat that allows him to add + 2 to his Parry Defense.

Defense(Parry) = 1d20 + 10 + 4 + 3 + 2.....he opts not to take the total/partial defense actions.

total defense= 1d20 + 18 (much higher than your 10)

They seem pretty darned equal. Maybe too equal? There is a near 50-50 chance here of hitting....The base defense could be scaled differently, this is just an example, and not optimized (I also use slightly different rules at home, but my group's into the 'tedious' style of combat). This, of course, assumes they are both fighters.....it gets more 'random' (different Defense/Attack ratios) with different classes/monsters- just as it should, even in current D&D.

These bonuses scale with power (A 4E trend I keep hearing about) and allow higher character/creatures to stomp lower ones....but still allows lower ones a slim chance...as real combat does.

So....if the First fighter does hit.....his damage would be:

2d6 + 6(1.5 STR) + 5(1/2 level)....or 2d6+11

subtract 6 for DR, and his max damage would be 17 pts of damage. These are not optimized builds or anything, just meager examples of how it works.
Conversely, that same fighter type decides to fight a 1st level fighter type.

This new, 1st level fighter has a Base Defense Bonus of +1 (assuming it is equal to level, like BAB), wears armor (DR 4) that allows him to apply 2 points of his Dexterity bonus to his defense (if Dodging), has a shield that provides a +2 bonus to defense, and has some sort of feat (like the current 'Dodge') that allows him to apply +1 to his Dodge Defense. He decides to Dodge, as he is a more Dextrous fighter.

Defense= 1d20 + 1(base defense) + 2(dex) + 1(feat) + 2(shield)

total defense= 1d20 + 6.......looks similar to a 1st level attack roll, doesn't it?

So, our 10th level fighter type decides to charge, cutting the whelp no slack..................

Who is likely to win this roll?

1d20+18 attack.........or.........1d20+6 defense?

The cannon-fodder fighter must roll at least a 13 to hope to defend himself- assuming his attacker rolls a 2.

Now, under these rules, ties go to the defender. Not tied d20 rolls unmodified, but TOTAL value of the attack/defense. Except on natural 1 or 20...........read my other posts.

So, if the 10th level fighter rolls a total of 24 (a 6 on the d20), the 1st level fighter has the chance to successfully defend himself by rolling a 18 (3 out of 20 chance) or higher!!!!! This is in favor of PCs, game-mechanic-wise, but also may allow for the lucky goblin/kobold/whatever mook to constantly defend himself. Some people really are that lucky.

Just my ideas and an example of application that doesn't utilize 20th level super-builds as I so often see used to illustrate rules balance. Hopefully the 1st vs. 10th example helps a bit too.

-Good Gaming
Using opposed rolls significantly changes the probability distribution as opposed to one side taking 10 (or 10.5 or 11), biasing it a lot more heavily in favour of the participant with the higher modifier.

Pretty sure that's wrong. It does change the probability distribution, by making it wider. That benefits the person who is looking for the less likely result, which would normally be the person with the lower modifier.

For instance: Bob has a +15 to attack, is trying to hit Gump with a +10 to AC.

With the normal rules, Bob only misses on a 1-4, a 20% chance. If both sides roll, Bob has a 191/400 = 48% chance to miss. (Assuming ties go to the attacker still, and saying an attack roll of 20 always hits but an attack roll off 1 always misses.)

Even more simply, say Bob has a +20 modifier to attack, vs Gump's +5 to defense. In the normal rules, Bob only misses on a 1. If both sides roll, he still misses if he rolls a 1, but he has more chances to miss if Gump rolls a 17 or better. Again it favors Gump.
Hmm. I've re-run the numbers and we are both wrong. To about +5 the difference between 1d20+X vs 11 and an opposed roll (ties win in both cases) is at about 2-3% absolute. Above +5, 1d20+X heads rapidly to 100%, while opposed rolls tail out more gradually.


Consider +15 vs +10, which is a net +5. If ties go to the attacker, Bob has an 80% chance of hitting or a 20% chance of missing (as you said).

In an opposed roll, any roll by Bob of 15 or over is an automatic win. So thats 30% win chance. Bob's minimum result is 6, so any roll by Gump of 6 or less is an automatic loss. That adds a further 70% * 30% = 21% (total 51%).

Thus, there's a 49% chance that we'll end up in the mid-range, where Bob rolls between 1 and 14 and Gump rolls between 7 and 20. That space covers 196 (14^2) possible rolls. Of these, 14 are ties, Bob wins 91 outright and Gump wins 91 outright. Ties go to Bob (for consistency with non-opposed rolls), so Bob gets 105/196, or 54%, of these contested rolls.

54% of 49% is 26%. Adding this to Bob's 51% gives a total of 77%. This is slightly less (not more, as I falsely said) than 80%, but it's a heck of a lot better than 52%!


Effectively, an opposed roll is (2d20 -21)+X vs 0, or 2d20+X vs 21. The range is twice as large as 1d20 (39 different results vs 20), but the results cluster more around the center. The increased range means that one can pretty safely drop the "auto-success / failure" rules, since it's possible (if unlikely) to succeed against a +19 or fail with a +18, in contrast to auto-failing against +11 or auto-succeeding with +9.


So yes, I agree that on a pure game mathematics basis opposed rolls are probably desirable wherever possible. However, there is a resolution time (and effort) cost associated with them that may or may not be a problem.
The Psionics rules use an opposed roll for the saving throws instead of a fixed value. I'm sure you could do the exact same thing with every roll. I believe that there is an optional rule in D&D that allows players to play with opposed rolls instead of the attacker rolling against a fixed value.

just a clarification. The pre 3.5 psionics rules used an opposed roll. I only knew 3.0 psionics and 3.5 psionics, but i know that in 3.5 it was the average (10+power level+mod) not opposed (1d20+power level+mod).
Our group used oposed rolls for a while then Stopped. At first it looked like a good idea but later as our characters got higher level it became more and more problematic.

1) it makes thins take longer. It adds an un-nececary extra strep to combat.

2) As you get higher in levels It seems to more or less favour those who have a 'good' base attack so fighters paladins etc. I found when i was playing my rogue once we hit 14-15 level using this system I was missing alot because my + to hit could not handle things if an already hard to hit monster happend to roll above 10 on his defense roll

Ultimately it was this second bit that lead to us no longer using it. Although the first was a real consideration.