Skull and Spine DR - shouldn't these scale?

[JCurwen3]

You get 2 DR for the Skull and 3 DR for the Spine (from Martial Arts) for free.

But surely these should be scaled, right? I thought the best approach would be to scale it to HP: 1 DR per 5 HP for the Skull, 1.5 DR per 5 HP for the Spine.

That way, you don't get the bizarre situation where the titan or dragon or T-rex with the extremely large frame (and correspondingly thick bones) gets no more protection than what a human gets. Or, for that matter, in a deci-scale (or below) creature in a mixed-size game, an inch tall humanoid with a whopping 2 DR when they don't even have that many HP.

Does this sound reasonable as a house rule?

[RyanW]

I have always considered doing the same, but haven't run into any creatures where it would come into play so I can't comment on how it works in play. Most of my games see [near] humans against [near] humans.

As an alternate, it could scale with SM. Look up the linear length in yards for the SM, and that's the skull DR (one higher SM for spine). So a SM+1 creature would have DR of 3 and 5, SM-1 DR 1 (or 2, depending on rounding) and 2. That would neatly keep all humans and near humans at the standard values.

[Grouchy Chris]

If you round to the nearest 5 HP, then a cat gets DR 1 to the skull. If you round down to a multiple of 5, then it gets 0. I think the former is better.

That would give a Tyrannosaur a skull DR of 7, where Lands out of Time sets it at DR 4. How thick is a T-Rex's skull, anyway?

[Anthony]

The actual amount of bone covering the skull and spine is pretty variable, and calling the skull DR 2 may be rather generous, but most animals have brains that are better armored (for their size) than human brains, just because the brain is a vital part and when your brain is the size of a walnut it isn't very hard to armor it. Still, the bones in a Tyrannosaurus skull look to be 5-10x thicker than equivalent human skull bones. To reach an elephant's brain from the front requires passing through more tissue and bone than a human torso.

[Gef]

Large critters need overall DR, too, so they don't break when they walk. Once you buy the extra overall DR and then add the 2 extra for the skull, I'm not sure you need to scale it further.

If you do scale it, be sure to do so for racial templates. A guy who works out builds his muscles and hence ST and hence HP, if that takes him past some threshold, though, it shouldn't make his skull thicker.

-GEF

[JCurwen3]

Originally Posted by Gef

Large critters need overall DR, too, so they don't break when they walk. Once you buy the extra overall DR and then add the 2 extra for the skull, I'm not sure you need to scale it further.

Has anyone ever speculated on what human overall DR is? I mean, yes, it's 0, but that's implicitly rounded down. There is some fractional DR that is normally below the resolution of the system.

Originally Posted by Gef

If you do scale it, be sure to do so for racial templates. A guy who works out builds his muscles and hence ST and hence HP, if that takes him past some threshold, though, it shouldn't make his skull thicker.

While that sounds sensible and true enough, is it actually true? I'm genuinely asking, because I have no clue.

At my peak weight (and a lot of it was fat and / or water), I was 109 kg or ~240 lbs (note I'm 1.95 m or ~6'5", so that was overweight but not terribly fat), my bone mass was significantly higher than it is now 77 kg or ~170 lbs. If I worked out and trained to get back to my previous weight (but this time in mostly muscle gain), then I am pretty sure from what I understand that my bone mass would be even greater than it had been back when there was more of me and it was mostly pudge. And you see weightlifters with those bowling ball sized shoulders often.

So that's why I'm curious - does the skull see any of that bone mass increase that comes from weight increase (esp muscle gain)? Is it evenly distributed or just specific to various selected body parts? My search skills failed to uncover an answer.

[Anthony]

Originally Posted by JCurwen3

While that sounds sensible and true enough, is it actually true? I'm genuinely asking, because I have no clue.

Yeah. There's nothing about working out that will modify the bones of the skull. Bone mass changes as a result of exercise or other stresses that affects the bones in question (and also generally doesn't change very fast), and there aren't really any skull exercises. It's possible that being hit on the head a lot will result in a thicker skull, but I suspect the brain damage occurs first.

[Gef]

What he said. The muscle attachement points for the skull are on the parts that GURPS calls "the back of the face". -GEF

[gilbertocarlos]

Maybe Squared root of HP/1,5 for spine, HP/3 for skull, that way, even with 100HP, you will have DR8 for spine and DR5-6 for the skull. for a Tyranosaur, it will be 3-4 for skull.

[JCurwen3]

Originally Posted by Gef

Large critters need overall DR, too, so they don't break when they walk. Once you buy the extra overall DR and then add the 2 extra for the skull, I'm not sure you need to scale it further.

If you do scale it, be sure to do so for racial templates. A guy who works out builds his muscles and hence ST and hence HP, if that takes him past some threshold, though, it shouldn't make his skull thicker.

Originally Posted by RyanW

As an alternate, it could scale with SM. Look up the linear length in yards for the SM, and that's the skull DR (one higher SM for spine). So a SM+1 creature would have DR of 3 and 5, SM-1 DR 1 (or 2, depending on rounding) and 2. That would neatly keep all humans and near humans at the standard values.

I think I might follow this SM-based approach, and make the DR increases built-in to having higher SM as a feature (it also helps to balance a little bit some of the problems inherent in higher SM that you get exactly [0] for). It also does have the benefit of preventing variability within the human size range.

GEF's right, basing it on HP would be problematic because it would have to be done at the racial level, and it seems that skull and spinal column width don't increase with mass (muscle or otherwise).

See, I'm not keen to charge for the extra DR. I normally would, but humans get there 2 DR (skull only) and 3 DR (spine only) for free. I know it goes against the GURPS standard which sets human average as the baseline, but I would almost kind of be happier if humans had to pay for their skull and spinal protection (it would fit more with the other GURPS idea of being generic); I mean, to build a race that has a head but a thin, fleshy skull you'd have to have Reduced DR 2 (Partial, Skull), which I'm not sure is RAW legal (negative or reduced DR, I mean). I'll play around ultimately with the various options and proposals, and may even settle on charging (or, for smaller creatures, crediting) for the DR and having it be just an advised suggestion for realistic higher and lower SM humanoids. I don't know, I'll see how it works out and what my players seem to prefer.