Size Modifier and Basic Move

[Varyon]

Originally Posted by whswhs

If we're doing realistic biomechanics, the stride length goes up as the limb length, but the time required goes up as the square root of the limb length. So movement speed increases as the square root of limb length, or the sixth root of body volume, if you go with the standard simplifying assumptions of GURPS; if you want exact physical realism, it's closer to the eighth root.

Bill Stoddard

That works out to somewhere around +1 SSR to Basic Move for every +2 SM (SM 0 is Move 5, SM+2 is Move 7, SM+4 is Move 10, etc) as a "realistic" base (as realistic as an SM+4 creature with the same body proportions as a human, anyway). For odd SM's, just go halfway between the two (round down).

[PK]

Originally Posted by Anders

Would it be reasonable to give a cost reduction to buy up Basic Move for high SM, similar to the one you get for ST?

I think it would be a very reasonable house rule. A high size is at least as correlated with walking speed as it is with strength.

However, I would limit it so that you could apply Size to the first (SM) levels of extra Move. Past that, you're limited to the same "up to +3 to Basic Move" that everyone else is, at full cost. (For example, at SM +4 you could buy at most Move+4 (Size, -40%) [12] and Move+3 [15].) This keeps things realistic.

(Please note that I'm not giving this any sort of official blessing, just saying that I wouldn't blink if my GM were to make it a house rule.)

[PK]

Originally Posted by Varyon

That works out to somewhere around +1 SSR to Basic Move for every +2 SM (SM 0 is Move 5, SM+2 is Move 7, SM+4 is Move 10, etc) as a "realistic" base (as realistic as an SM+4 creature with the same body proportions as a human, anyway). For odd SM's, just go halfway between the two (round down).

At anything resembling "PC scale," this can be further simplified to +1 Move per +1 SM. That assumption doesn't really "break" IMO until SM +5 or +6, which is extremely rare for any character for which point cost matters.

[Anthony]

Originally Posted by whswhs

If we're doing realistic biomechanics, the stride length goes up as the limb length, but the time required goes up as the square root of the limb length.

That assumes no change in stride pattern, which is not clearly valid, though it's correct for any given stride pattern; see the Walking Froude Number.

[Curmudgeon]

Growth on p.50 of Powers suggests Enhanced Move as opposed to Basic Move when reflecting an increased stride due to size.

[ErhnamDJ]

The only reason I can see to give a price discount on a trait is if it's less useful. This explains why No Fine Manipulators gives a discount on DX: creatures without fine manipulators can't use most of the benefits DX provides.

How is moving quickly less useful to large creatures than small creatures? It's less useful to a mammoth than to a bison, and less useful to a bison than to a rabbit, and less useful to a rabbit than to a mosquito?

If move is worth more to smaller creatures than it is to humans, how much more should they pay for it?

[Anthony]

Originally Posted by ErhnamDJ

The only reason I can see to give a price discount on a trait is if it's less useful.

This gets into the 'why is SM a price discount on ST'. It makes some sense for lifting ST, since a lot of the reason you buy lifting ST is because it lets you wear more armor and SM makes your armor heavier, but that maxes out at maybe -20% on your ST as a whole, and it certainly isn't relevant to striking ST or HP, except in the way it's also relevant to move: you can't use those abilities in places you can't fit in to.

[ErhnamDJ]

Originally Posted by Anthony

This gets into the 'why is SM a price discount on ST'.

I think the reason there's a discount for ST on large creatures is that high ST is overpriced for everyone, but only large creatures tend to purchase it, so that kinda-sorta does something about it. I would rather lower the price of higher ST and remove the discount large creatures receive.

It makes some sense for lifting ST, since a lot of the reason you buy lifting ST is because it lets you wear more armor and SM makes your armor heavier

That might make sense for some characters, like elephants, but certainly not for supers, where being able to lift heavy things is worth about as much as being able to punch hard.



I think being large is a significant disadvantage and should give back points for that, but I think it would be better to handle that as a direct disadvantage than trying to sneak those points back in through discounts on things large creatures might not buy.

[Anthony]

Originally Posted by ErhnamDJ

I think the reason there's a discount for ST on large creatures is that high ST is overpriced for everyone.

Oddly enough, the SM discount to ST works out pretty close to 60 points per step on the range/speed chart:
SM +1, ST 15: 45
SM +2, ST 20: 80
SM +3, ST 30: 140
SM +4, ST 45: 210
SM +5, ST 70: 300
SM +6, ST 100: 360
SM +7, ST 150: 420
SM +8, ST 200: 380

Given that, I'd be tempted to make Size cost 60 (or perhaps less, if we think it's miscosted) and actually multiply your ST/HP (or maybe ST/HP/DR for a cost of 75)

[ErhnamDJ]

Originally Posted by Anthony

Given that, I'd be tempted to make Size cost 60 (or perhaps less, if we think it's miscosted) and actually multiply your ST/HP (or maybe ST/HP/DR for a cost of 75)

I use rules I got from T-Bones's site. I think they make this easier for supers, where high ST is really overpriced. With these rules, there's no discount for size, so size needs to be priced separately. They go like:

10 [0]
15 [25]
20 [50]
30 [75]
50 [100]
70 [125]
100 [150]
150 [175]
200 [200]
300 [225]
And so on...