I'm putting this here mostly to make sense of this myself, but hopefully some of you can benefit form this, or correct any errors I might have made, which would be even better.
CMB = Base attack bonus + Strength modifier + special size modifier
So far pretty simple.
Performing a Combat Maneuver: When performing a combat maneuver, you must use an action appropriate to the maneuver you are attempting to perform. While many combat maneuvers can be performed as part of an attack action, full-attack action, or attack of opportunity (in place of a melee attack), others require a specific action. Unless otherwise noted, performing a combat maneuver provokes an attack of opportunity from the target of the maneuver. If you are hit by the target, you take the damage normally and apply that amount as a penalty to the attack roll to perform the maneuver. If your target is immobilized, unconscious, or otherwise incapacitated, your maneuver automatically succeeds (treat as if you rolled a natural 20 on the attack roll). If your target is stunned, you receive a +4 bonus on your attack roll to perform a combat maneuver against it.
Allright, so the bolded parts modify CMB. Still pretty easy to figure out, though I can't see why stunned opponents grant attacker's CMB instead of reducing their own CMD.
When you attempt to perform a combat maneuver, make an attack roll and add your CMB in place of your normal attack bonus. Add any bonuses you currently have on attack rolls due to spells, feats, and other effects. These bonuses must be applicable to the weapon or attack used to perform the maneuver. The DC of this maneuver is your target's Combat Maneuver Defense. Combat maneuvers are attack rolls, so you must roll for concealment and take any other penalties that would normally apply to an attack roll.
Right, now it gets kind of complicated. So my CMB is actually STR + BAB + Special Size modifier + 4 if opponent is stunned - damage taken from AoO + other bonuses.
I think other bonuses are things like improved [maneuver], weapon focus, weapon's enhancement bonus, bless, inspire courage and so on. Interestingly only bonuses, but not penalties are added to CMB, so I can use power attack when dealing damage in a grapple check at no penalty to my CMB, or use maneuvers while prone at no penalty.
Finally, concealment affects combat maneuvers.
Right. Let's move on to CMD.
Combat Maneuver Defense: Each character and creature has a Combat Maneuver Defense (or CMD) that represents its ability to resist combat maneuvers. A creature's CMD is determined using the following formula:
CMD = 10 + Base attack bonus + Strength modifier + Dexterity modifier + special size modifier
So far simple.
The special size modifier for a creature's Combat Maneuver Defense is as follows: Fine –8, Diminutive –4, Tiny –2, Small –1, Medium +0, Large +1, Huge +2, Gargantuan +4, Colossal +8. Some feats and abilities grant a bonus to your CMD when resisting specific maneuvers. A creature can also add any circumstance, deflection, dodge, insight, morale, profane, and sacred bonuses to AC to its CMD. Any penalties to a creature's AC also apply to its CMD. A flat-footed creature does not add its Dexterity bonus to its CMD.
And here it gets difficult. CMD is actually 10 + STR + DEX + BAB + Special Size Modifier + deflection + dodge + insight + morale + profane + sacred - any penalties at all to AC.
It's important to note that CMD is not the same as touch AC + CMB, even for medium sized creatures who don't have multiply size modifier to AC by -1. For example, cover and luck bonuses are added to touch AC, but not CMD.
Oh yeah, and if you're denied Dex bonus to AC, you lose it from your CMD. I assume this means I also lose dodge bonuses from CMD, but that's not explicitly stated anywhere.
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I think other bonuses are things like improved [maneuver], weapon focus, weapon's enhancement bonus, bless, inspire courage and so on. Interestingly only bonuses, but not penalties are added to CMB, so I can use power attack when dealing damage in a grapple check at no penalty to my CMB, or use maneuvers while prone at no penalty.
Um.
When you attempt to perform a combat maneuver, make an attack roll and add your CMB in place of your normal attack bonus. Add any bonuses you currently have on attack rolls due to spells, feats, and other effects. These bonuses must be applicable to the weapon or attack used to perform the maneuver. The DC of this maneuver is your target's Combat Maneuver Defense. Combat maneuvers are attack rolls, so you must roll for concealment and take any other penalties that would normally apply to an attack roll.
It was the last sentence of the thing you quoted. :)
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As I have been vocal about elsewhere this is the one facet that is a cross to bear for me.
I enjoyed the simplicity of the utilization in the Beta rules that we playtested.
I'll admit it probably wasn't the most complete aspect and there were many modifiers and circumstances that were never accounted for - in other words it wasn't realistic enough; but I was happy to overlook the realism for the sheer simplistic nature of it.
One DC. One Die roll. One total to add to it.
It wasn't comprehensive; but sleek and simple, and made the adjudication easy and move on.
It's the one thing that I've house-ruled back to the way Beta had it. So far the rest of the changes, I'm quite happy over.
Robert
Kairu Kage pointed out that the biggest grievance is accounted for, penalties do count for maneuvers. Jeez, that would have been quite an oversight!
As for Luck bonuses and such not counting to CMD, I dunno, I just use Touch AC anyway. But a strict interpretation of "Attack Rolls" would mean that cover applies because it's an attack roll. It's just not mentioned in the formula, just like it is not explicitly mentioned in the AC formula to my knowledge. Likewise for a "+x Luck bonus to attack rolls." I would read from this that CMD is virtually the same as Touch AC + CMB.
So all you really need to bear in mind is that Stunned +4 and Damage from AoO modifier. That's not so complex.
Still pretty easy to figure out, though I can't see why stunned opponents grant attacker's CMB instead of reducing their own CMD.
CMD is reduced, in addition to your +4 bonus to CMB checks.
Any penalties to a creatures AC also apply to its CMD
So, your stunned opponent would also suffer an aditional -2 to AC/CMD, in addition to losing the benefit of a Dex modifier.
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It's a little involved, I'll grant you, but it is a lot easier to figure out on-the-fly if you already have the base CMB/CMD listed in the stats. We've been using things like Charge, Barbarian Rage, and buff spells to fiddle with attack, damage, and AC. Since most of those things affect combat maneuvers in a similar way, it's just a matter of being sure CMB/CMD are changed as well.
It's actually refreshing to me that these numbers need to be watched. I got so used to rogues auto-succeeding on every tumble check and large monsters auto-grappling every player for a round, after which they auto-succeeded on their escape artist checks and began the cycle all over again. Red Hand of Doom was particularly annoying with those spiked chain monks. "You're grappled. You escape. Wash, rinse, repeat."
When you attempt to perform a combat maneuver, make an attack roll and add your CMB in place of your normal attack bonus. Add any bonuses you currently have on attack rolls due to spells, feats, and other effects. These bonuses must be applicable to the weapon or attack used to perform the maneuver. The DC of this maneuver is your target's Combat Maneuver Defense. Combat maneuvers are attack rolls, so you must roll for concealment and take any other penalties that would normally apply to an attack roll.It was the last sentence of the thing you quoted. :)
Great, one less error I'll make when I play. :)
CMD is reduced, in addition to your +4 bonus to CMB checks.
It's intuitive that things that affect attacker are calculated into attacker's attack roll, spell DC, or CMB and things that affect defender are calculated into defender's AC, saves or CMD. Stun breaks this by granting an attacker bonus for a condition that the defender is suffering from. Mathematically it's the same thing, but at least for me it's easier to remember to only check for my own conditions, statuses and buff spells when calculating my CMB.
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Still pretty easy to figure out, though I can't see why stunned opponents grant attacker's CMB instead of reducing their own CMD.CMD is reduced, in addition to your +4 bonus to CMB checks.
Any penalties to a creatures AC also apply to its CMDSo, your stunned opponent would also suffer an aditional -2 to AC/CMD, in addition to losing the benefit of a Dex modifier.
Stunned is one of the conditions that I truly don't like: there is no way to bring an ally out of the "Stunned" condition. :(
There are spells or other ways to help with fatigue/exhaustion, shaken/frightened/cowering/panicked, and dazed/confused. But nothing for stunned. I don't recall the spell that applies the Stunned state, but it's ridiculous to try to avoid or fix.
Stunned is one of the conditions that I truly don't like: there is no way to bring an ally out of the "Stunned" condition. :(
12th level paladin mercy right off the top of my head.
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My major beef with the way this system currently works: it is way too easy to grab little creatures. For example, out of the bestiary preview a rat has a CMD of 6 (10 for trips). That means a theoretical 1st level fighter with 15 str only needs to roll a 3 to grapple it. That makes sense once he already has a hold of the thing, but should it really be that easy to grab a tiny, quick little creature that does not want to be caught? This is of course due to the fact that size modifiers are negative for smaller creatures when it comes to CMB/CMD, which makes sense some of the time. Look at the other side for instance: it is probably easy enough to grab a hold of the enraged bull, but good luck wrestling it to the ground.
So, two house rules that have been proposed:
1) Require two rolls. First the attacker must make a melee touch attack, and then, if successful, roll standard CMB vs. CMD. The pro to this is that it is more realistic and the con is that it adds an extra die roll every time someone wants to use a maneuver. The fact that it may make maneuvers a bit harder to pull off may be seen as positive or negative depending on your viewpoint.
2) One roll made against either the opponent's touch AC or their CMD, whichever is higher. This allows for the idea that the little guys may be too quick to get a hand on them, but if you do you got them, and it is easy to grab the bigguns but good luck shifting them. The neg is having to pay attention to which number to use with each opponent.
Thoughts?
1) Require two rolls. First the attacker must make a melee touch attack, and then, if successful, roll standard CMB vs. CMD. The pro to this is that it is more realistic and the con is that it adds an extra die roll every time someone wants to use a maneuver. The fact that it may make maneuvers a bit harder to pull off may be seen as positive or negative depending on your viewpoint.
That's virtually the same as 3.5 isn't it?
2) One roll made against either the opponent's touch AC or their CMD, whichever is higher. This allows for the idea that the little guys may be too quick to get a hand on them, but if you do you got them, and it is easy to grab the bigguns but good luck shifting them. The neg is having to pay attention to which number to use with each opponent.Thoughts?
Hm. Interesting idea.
In general, it's not such a big problem for me. Your example is a fighter catching a rat, but an equivalent example that's far more likely to come up is a human being and a Huge dragon. I think most people have no problem reconciling the latter, your opinion may differ.
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My major beef with the way this system currently works: it is way too easy to grab little creatures.
Isn't that the way the system always worked? I'm not an expert on grabbing little creatures, but we're not talking about catching them while they're running away. You can only grab someone who's within your threatened range, so it's not so different from trying to land a hit on a quick little guy, except you're trying to hit them with your whole body instead of an arrow or a club.
Grapple has always been a horror show for small creatures when much larger creatures try to grab them. A dragon is pretty sure to mash a halfling between its teeth, and that's as it should be. If you're little and you get within threat range of something that size...well, good luck. = )
2) One roll made against either the opponent's touch AC or their CMD, whichever is higher. This allows for the idea that the little guys may be too quick to get a hand on them, but if you do you got them, and it is easy to grab the bigguns but good luck shifting them. The neg is having to pay attention to which number to use with each opponent.
I'm not sure it's appropriate to treat grapple and other combat maneuvers as though you're just trying to get a hand on them. The rule reads that you can't use only one hand without a penalty, so you're already covered on that front. It wouldn't be fair to say a fighter who drops his weapon and tries to grab a gnome with both hands is the same as a fighter trying to hit an AC. Wrapping your arms around someone is much more involved and ends up being somewhere between a touch and a standard attack, which is what CMB/CMD is meant to emulate.
It's also just as dangerous to be the grappler as it is to be the little guy they're holding. Rogues can go to town on you, and anyone else for that matter since you both have the same penalties in a grapple. I think that's a fair trade-off for the risk to small characters in the party. Sure, they're the easiest to grapple, but that grapple is going to lower their attacker's precious AC...depending on the initiative order, the grapplee could delay his attempt to escape, let the party go to town on the grappler, then (hopefully) slip right out of the hold.
That's my read on the Combat Maneuver rules, anyway.