Advantage that only applies to a hit location

[nick_coffin]

I'm trying to create an ability for my DF game in which one of the effects is that the target's DR is increased by +1 to his arms only. What would be the limitation value for this?

The right arm is hit on a roll of 8, while the left arm is hit on a 12. That's a 46 in 216 chance of it occurring if my math is correct, or 21.3%. From the table on PU8, page 4, the percentage of time that the ability works, the range 19-31% is a -30% limitation.

Did I just answer my own question?

[ravenfish]

On Basic Set p.47, the "Partial" limitation to Damage Resistance provides provides the canonical limitation values for Damage Resistance that only protects a specific body part: a 10% limitation value per -1 to target that hit location, doubled if only protecting one limb/extremity out of a pair (or -10% for "torso only"). Mind you, I feel this to be horribly stingy, even by the standards of GURPS limitations, and suspect that your idea probably would result in fairer cost.

[Varyon]

Personally, I prefer to scale the cost of DR the same way the cost of armor scales - with straight percentage coverage. Use either the % coverage from LT (but divide by 3, since full armor is 300%) or figure out the square footage of coverage via one of the Pyramid Armor Design articles and divide by the 21.35 square feet of full coverage.

This arguably gives the character too much of a discount, but I'm fine with encouraging players to build characters with imperfect DR. This could be applied to other Advantages as well, but you'll want to be careful - it's probably fine for Regeneration, but not so much for Regrowth (since the latter generally only has a gameplay impact on the limbs and extremities).

[Ulzgoroth]

What exactly would be the mechanics of Regeneration with Partial?

[Refplace]

Originally Posted by Ulzgoroth

What exactly would be the mechanics of Regeneration with Partial?

It would only heal damage to that location. That means tracking HP by location so it would add bookkeeping to most campaigns.

[Varyon]

Originally Posted by Ulzgoroth

What exactly would be the mechanics of Regeneration with Partial?

Originally Posted by Refplace

It would only heal damage to that location. That means tracking HP by location so it would add bookkeeping to most campaigns.

What he said. Granted, the additional book-keeping wouldn't be horrible - you'd only need to note the location struck when it's one of the odd men out. That is, if you have Fast Regeneration (Right Arm Only) [5]*, you only need to track hits to the right arm separately. If you have Fast Regeneration (Not on the Legs/Feet) [32], you only need to track hits to the legs/feet separately.

*Yes, this is less than 20% of the cost of the trait. I feel it's appropriate to simply multiply by coverage, rather than have a -n% modifier.

[Ulzgoroth]

Originally Posted by Refplace

It would only heal damage to that location. That means tracking HP by location so it would add bookkeeping to most campaigns.

Having HP by location wouldn't just be housekeeping, it would be a major new rule system.

Unless you just mean noting a hit location for all damages...except the ones that actually have no hit location, like systematic poison or large-area injuries...

[Refplace]

Originally Posted by Ulzgoroth

Having HP by location wouldn't just be housekeeping, it would be a major new rule system.

Unless you just mean noting a hit location for all damages...except the ones that actually have no hit location, like systematic poison or large-area injuries...

We already have something similar or crippling wounds.

[malloyd]

Originally Posted by Refplace

It would only heal damage to that location. That means tracking HP by location so it would add bookkeeping to most campaigns.

Keep in mind that should you do this, you are going to start running into all sorts of edge cases that are going to need additional rulings. The one that immediately comes to mind here is how do you split up damage that applies to the entire body - the dragonfire burnt the entire front of your body but only your arms heal faster, so....

Look at how the rules for DR expand from a very simple rule (subtract DR from any damage roll) to stuff like how much DR applies to eyeslits, chinks in armor, large area injury, sealed vs. unsealed.... The rules for DR have already been worked out for you long ago, but for most other stuff you're going to have to make it up. Be prepared for that.

[Varyon]

Originally Posted by malloyd

Keep in mind that should you do this, you are going to start running into all sorts of edge cases that are going to need additional rulings. The one that immediately comes to mind here is how do you split up damage that applies to the entire body - the dragonfire burnt the entire front of your body but only your arms heal faster, so....

Look at how the rules for DR expand from a very simple rule (subtract DR from any damage roll) to stuff like how much DR applies to eyeslits, chinks in armor, large area injury, sealed vs. unsealed.... The rules for DR have already been worked out for you long ago, but for most other stuff you're going to have to make it up. Be prepared for that.

Yeah, Large Area Injury is potentially problematic for something like Regeneration (Arms Only). With that said, it probably wouldn't be terrible to simply multiply the injury by the relative surface area of the quickly-regenerating area to determine how much of the injury benefits from Regeneration. You could technically extend this for determining if limbs/extremities were crippled by the attack. If doing so, you may be able to do away with the simplification of the default Large Area Injury rules (use average of Torso DR and the DR of the worst-protected location) - roll damage normally, assess it against each hit location's DR separately, then multiply the resulting injury by relative surface area (you'd want to keep a chart for surface area handy - or better yet, a spreadsheet that lets you plug damage in and get injury). So, say a character wearing DR 5 plate on the Torso, a DR 4 plate vambrace (2/6 protection) on the right arm, and DR 3 mail everywhere (including under the plate on the Torso and forearm), and gets hit by an area-effect fireball that deals 8 burn. The Torso takes no damage, the forearm would have 1 point of penetrating damage, the Skull would have 3 points of penetrating damage, and everywhere else would have 5 points of penetrating damage. Starting from the top, that's (3*4*0.066=)0.79 injury to the Skull; (5*0.033=)0.16 injury to the Face (from these, we can infer the Eyes didn't take enough injury to risk crippling); (5*0.017)0.08 injury to the Neck; 0 damage to the Torso; (5*4/6*0.082=)0.27 injury to the right shoulder/upper arm/elbow; (1*2/6*0.082=)0.03 injury to the right forearm; (5*0.082=)0.41 injury to the left Arm; (5*0.016=)0.08 injury to each Hand; (5*0.16=)0.82 injury to each Leg; and 0.08 injury to each Foot (same surface area as Hand). That's insufficient to cripple anything, and works out to total penetrating injury of (0.79+0.16+0.08+0.27+0.03+0.41+2*0.08+2*0.82+2*0.0 8=)4 injury total. Interestingly, this is more damaging than you'd see using the normal rules - using the average of Torso DR (8) and the lowest DR (3), for 5.5, round up to 6, means only 2 injury.

Of course, even with a chart of % body coverage, this probably wouldn't be a terribly quick calculation, so you wouldn't want to do it without some sort of assistance from a spreadsheet or similar. Much less problematic if you do the RAW way (average Torso and lowest), then just multiply by % coverage (in the above case, 2*0.082=0.164, so too little injury to even bother with the effects of one-arm Regeneration).