Help me template a new house rule.

[Celebrim]

One thing that has bothered me about D20 for a long time now is that a horse 200 yards away is just as hard a target it is just standing there looking at you, or if its galloping all out at 40 mph perpendicular to your facing.

I'd like to fix this with a house rule that gave moving targets an additional dodge bonus.

I could do this very simply by simply giving a moving object a +1 dodge bonus per 40' that it moves in a round (rounded down).

v1.0: Whenever you move at least 40' in a round, you gain a +1 dodge bonus to your AC versus missile attacks for each full 40' you move. This bonus lasts until the beginning of your next turn.

This - however simple - is fraught with subtle problems both from the standpoint of balance and the standpoint of realism. The balance problem is abit obvious. Charging Barbarians are harder to hit than intended. It's not serious, but it's also not my intention to make a Barbarian charging straight at you harder to hit.

From the standpoint of realism, this problem arises because a target moving straight at you is generally easier to hit than one moving perpendicular to you because the apparant motion is higher in the latter case. This can be modelled by drawing a circle around the attacker. If the target's motion lies on a line which crosses within the circle, then the apparant motion is not sufficient to throw off the attacker's aim.

v1.1: Whenever you move at least 40' in a round, you gain a +1 dodge bonus to your AC versus missile attacks for each full 40' you move. You only gain this bonus with respect to attackers that you do not pass within 10', and only if your line of motion does not when extended or regressed infinitely pass within 10' of the attacker. This bonus lasts until the beginning of your next turn.

That's better, but's its ugly and I need clearer wording so that ideally every 12 year old can figure out what I mean.

But, we are also not finished with the complexity.

The above rule is adequate so long as we are all using laser weapons or magical rays, but most weapons are enough ballistic in thier flight that rapidly changing in the ranges to the target present just as much of a problem was changes in the direction to the target. Firearms are only barely balistic, but if we move the range out far enough we'll be forced to accept that a target moving rapidly toward or away from us is going to require subtle continious changes in aim. Most D&D missile weapons are even more ballistic and require at a distance large changes in elevation to compensate for changes in range. Some weapons - like say mortars, howizters, and trebuchets - are entirely balistic.

And there is an additional problem. What about movement that isn't in a straight line?

v1.2 Whenever you move at least 40' in a round, you gain a +1 dodge bonus to your AC versus missile attacks for each full 40' you move. You only gain this bonus with respect to attackers that you do not pass within 10', and only if your line of motion at any point during the turn does not when extended or regressed infinitely pass within 10' of the attacker. This bonus lasts until the beginning of your next turn.
If the attacker wields a firearm, you gain the dodge bonus regardless of your line of motion if you are more than 5 range increments from the attacker. If the attacker uses a non-firearm missile weapon - such as all hurled weapons or bows, you gain the dodge bonus regardless of your line of motion if you are more than 3 range increments from the attacker. You always gain the dodge bonus against howitzers, mortars, catapolts, trebuchets and all similar artillery weapons regardless of your line of motion.

The above rule covers most situations, but if you get in a chase sequence with a target, the relative motion between the targets depends on thier difference in relative speeds. Again this leaves us with unwieldy caveats.

v1.3 Whenever you move at least 40' in a round, you gain a +1 dodge bonus to your AC versus missile attacks for each full 40' you move. You only gain this bonus with respect to attackers that you do not pass within 10', and only if your line of motion at any point during the turn does not when extended or regressed infinitely pass within 10' of the attacker. This bonus lasts until the beginning of your next turn.
If the attacker wields a firearm, you gain the dodge bonus regardless of your line of motion if you are more than 5 range increments from the attacker. If the attacker uses a non-firearm missile weapon - such as all hurled weapons or bows, you gain the dodge bonus regardless of your line of motion if you are more than 3 range increments from the attacker. You always gain the dodge bonus against howitzers, mortars, catapolts, trebuchets and all similar artillery weapons regardless of your line of motion.
If the attacker is also moving and traveling in the same line as the target, the defender must subtract the attacker's speed from his own for the purposes of determing the size of his dodge bonus due to movement.

That's as far as I've gotten, and I don't particularly like it. Does anyone know of a product that addresses this issue already? Can anyone think of a better wording to clarify my meaning?

 

[BarkingDeathSquirrel]

One thing that has bothered me about D20 for a long time now is that a horse 200 yards away is just as hard a target it is just standing there looking at you, or if its galloping all out at 40 mph perpendicular to your facing.

I'd like to fix this with a house rule that gave moving targets an additional dodge bonus.

I could do this very simply by simply giving a moving object a +1 dodge bonus per 40' that it moves in a round (rounded down).



This - however simple - is fraught with subtle problems both from the standpoint of balance and the standpoint of realism. The balance problem is abit obvious. Charging Barbarians are harder to hit than intended. It's not serious, but it's also not my intention to make a Barbarian charging straight at you harder to hit.

From the standpoint of realism, this problem arises because a target moving straight at you is generally easier to hit than one moving perpendicular to you because the apparant motion is higher in the latter case. This can be modelled by drawing a circle around the attacker. If the target's motion lies on a line which crosses within the circle, then the apparant motion is not sufficient to throw off the attacker's aim.



That's better, but's its ugly and I need clearer wording so that ideally every 12 year old can figure out what I mean.

But, we are also not finished with the complexity.

The above rule is adequate so long as we are all using laser weapons or magical rays, but most weapons are enough ballistic in thier flight that rapidly changing in the ranges to the target present just as much of a problem was changes in the direction to the target. Firearms are only barely balistic, but if we move the range out far enough we'll be forced to accept that a target moving rapidly toward or away from us is going to require subtle continious changes in aim. Most D&D missile weapons are even more ballistic and require at a distance large changes in elevation to compensate for changes in range. Some weapons - like say mortars, howizters, and trebuchets - are entirely balistic.

And there is an additional problem. What about movement that isn't in a straight line?



The above rule covers most situations, but if you get in a chase sequence with a target, the relative motion between the targets depends on thier difference in relative speeds. Again this leaves us with unwieldy caveats.



That's as far as I've gotten, and I don't particularly like it. Does anyone know of a product that addresses this issue already? Can anyone think of a better wording to clarify my meaning?

Another option might be to just make take the first option and make it a feat. Certainly less realistic... but the balance is better. But... *shrugs

 

[Ferrix]

Too complex, I'd make it simple and go with the first one.

 

[Hodgie]

I am wondering if you are aware that running does indeed improve your armor class against missile weapons. You gain a +2 bonus against them (but lose any dexterity bonus unless you have the Run feat).

 

[Psimancer]

Here is a simple solution that just popped into my head while reading the post; add the targets movement to its effective range. You may just want to do movement in excess of 30 ft. or something…

 

[Celebrim]

I am wondering if you are aware that running does indeed improve your armor class against missile weapons. You gain a +2 bonus against them (but lose any dexterity bonus unless you have the Run feat).

For many or most PC's, that would mean running actually worsened thier AC versus missile weapons. And note that while it might be semi-realistic to suggest that you are better off standing thier trying to dodge incoming arrows than simply taking off running (though I don't buy that), its completely unrealistic to suggest that the same would be true versus a guy with a handgun.

Another option might be to just make take the first option and make it a feat. Certainly less realistic... but the balance is better. But... *shrugs

I've already got a few feats in mind. IMO though, the worst sin a feat designer can commit is to take something that everyone ought to be able to do and make it such that you can only do it if you have a feat. Maybe you can only do it well with a feat, maybe you are exceptionally good at doing it with a feat, but ordinary manuevers don't require feats. If you want to design a cool new feat, first design rules for what happens when you don't have the feat, and then let the feat modify or break those rules in some way.

Here is a simple solution that just popped into my head while reading the post; add the targets movement to its effective range. You may just want to do movement in excess of 30 ft. or something…

That's actually not too bad. It handles the problem of balistics by noting that non-balistic weapons tend to have large range increments. On the other hand, it makes the problem of charging opponents being too hard to hit even worse, especially for a hurled weapon like a javelin or a hand axe. And it doesn't feel right to me with regards to something like the long bow either, since the long bow will basically be able to ignore the motion of targets. But, in my experience, its a darn good archer that can hit any sort of moving target at beyond 40 yards. Hitting a moving target with a bow is nothing like hitting a movie target with a firearm, because the projectile is only moving at about 1/10th the speed of a bullet.