Costs Fatigue, Variable

GURPS Power-Ups 8 p 12 intended for Innate Attack but...
*Use the same method to add a variable FP cost to nonattack abilities that come in levels; just substitute levels of effect for dice.
*Abilities other than attacks don’t need the Variable enhancement to use this option.
This appears to be one way that you can get values of less than -5% for Costs Fatigue, if the average FP cost is less than 1. For example:
*1. Set the FP cost to use the ability at full effect: 1
*1.5: maximum dice damage? 10
*2. Divide this maximum FP cost by the attack’s maximum dice of damage to find the FP cost per die: 1/10=0.1
*2.5: average dice damage? (1+10)=11, 11/2=5.5
*3. Multiply cost per die by “average” damage dice – (1 + maximum dice)/2 – to find average FP cost: 0.1 x 5.5 = 0.55
*3.5 0.55 x 5% = 2.75%
*4. Drop all fractions: -2%
However it would probably be simpler to just take -5% as Partially Limited Abilities on the higher levels so that the lower ones are free. RAW 0.1 FP would round up to 1 FP anyway, but this would be an option if someone wanted to keep track of 1/10 FP expenditures.
==Laser Lad==
:Laser Lad has Burning Attack 10d with Variable and Costs Fatigue.
:His FP cost at full effect is 20.
:His attack requires 20/10 = 2 FP per die.
:“Average” damage dice are (1 +10)/2 = 5.5d,
:so average FP cost is 2 x 5.5 = 11 FP.
:He takes Costs Fatigue 11, for -55%.
:When he attacks, he pays
:2 FP for 1d,
:4 FP for 2d,
:and so on,
:to a maximum of 20 FP for 10d.
The problem with the given example is it does not exhibit the 4th step "Drop all fractions" which follows finding the average FP cost, because there are no fractions at that point. When "cost per die" is a multiple of 2, multiplying it by the average will always result in a non-fraction. So it doesn't make it clear WHEN fractions are dropped. This problem becomes apparent when tweaking the example to make it half as fatiguing:
:Laser Lad has Burning Attack 10d with Variable and Costs Fatigue.
:His FP cost at full effect is 10.
:His attack requires 10/10 = 1 FP per die.
:“Average” damage dice are (1 +10)/2 = 5.5d,
:so average FP cost is 1 x 5.5 = 5.5 FP.
:He takes Costs Fatigue 5.5, for -27.5%.
:When he attacks, he pays
:1 FP for 1d,
:2 FP for 2d,
:and so on,
:to a maximum of 10 FP for 10d.
At what point here is the fraction dropped? Two possibilities appear to exist:
*reducing -27.5% to -27%
*reducing average FP cost from 5.5 to 5, worth -25%
This can be further complicated with a 3rd possibility:
:Laser Lad has Burning Attack 10d with Variable and Costs Fatigue.
:His FP cost at full effect is 5.
:His attack requires 5/10 = 0.5 FP per die.
:“Average” damage dice are (1 +10)/2 = 5.5d,
:so average FP cost is 0.5 x 5.5 = 2.75 FP.
:He takes Costs Fatigue 2.75, for -13.75%.
:When he attacks, he pays
:0.5 FP for 1d,
:1 FP for 2d,
:and so on,
:to a maximum of 5 FP for 10d.
If "FP per die" is rounded down to 0, this would ruin the equation because average FP cost would be 0 too, and the limitation would be worth nothing at all.
What should probably happen is following the above, but rounding up final FP costs, so 0.5 FP costs 1 FP so you may as well do a 2d attack unless you're trying to avoid hurting someone.
Partial Dice also make this very complicated since it can work with 0.25 or 0.3.
==see also==
*Ascending Limitations
*Declining Enhancements
Category:Limitations