Multiplicative Limitations Beyond -80%

[vierasmarius]

The Multiplicative pricing system is attractive in that it allows meaningful limitations to powers that have large enhancements. A -50% limitation on a power with +400% enhancements (not inconcievable with Cosmic etc) gives a net cost of x4.5 base price, but with Multiplicative it becomes x2.5. However, because no limitations can exceed -80%, there are many situations where additional, appropriate limitations would make no sense from a point-budget perspective.

Here's my idea: The first -80% of limitations reduces the cost as normal for Multiplicative pricing. The next -80% reduces the remainder, the next -80% does the same, etc. For example, a power with a base cost of 100 has +100% in Enhancements and -180% in Limitations. Under normal Additive pricing it would cost (100*(1+1.00-1.80)) 20 points, while under Multiplicative it would cost (100*(1+1.00)*(1-1.8; min 0.2)) 40 points. Under my proposal it would cost (100*(1+1.00)*(1-0.8)*(1-0.8)*(1-0.2)) 6.4 points.

To put it another way, the first -80% reduces the price to 20% normal. The next -80% is applied to that 20% (reducing it to 4%), and the remaining -20% reduces that to 3.2%.

Any thoughts on this? I feel it's fair in the context of Multiplicative Modifiers, which can already lead to dramatic cost reductions compared to the Additive method. If you feel it's too severe a reduction, it could be limited to a minimum equal to 20% of the base cost, which would still preserve some of the benefit of limitations beyond -80%. For instance, the example power above could be given up to -130% in limitations (ie, -80% and -50%) before hitting limit of the 20% of base price.

[Blind Mapmaker]

The problem you describe crops up some of the time, but I think it's just one of the features of using multiplicative modifiers. It mostly occurs when closely modelling abilities from fiction, other RPGs etc. It may be annoying in the case of an individual character, but on the whole it tends to balance out. In other words, with additive modifiers you try to maximize limitations, under multiplicative modifiers you try to reign in enhancements.

Your proposal is the "best of both worlds" and I feel this is just too good a deal in most cases. I would only be tempted to use it for Afflictions, but their pricing is off anyway.

[vierasmarius]

Originally Posted by Blind Mapmaker

Your proposal is the "best of both worlds" and I feel this is just too good a deal in most cases. I would only be tempted to use it for Afflictions, but their pricing is off anyway.

Well, that's why I offered the option of limiting it 20% of base cost. This way, the absolute minimum cost of powers is the same between both models. As written, the minimum cost in Multiplicative is 20% of the Enhanced cost.

Afflictions have their own issues, which are exacerbated by Additive modifiers...

[munin]

I'm sure this exact suggestion has popped up before on the forums (for both additive and multiplicative modifiers), and generally not been hated, but I can't find it. Bah.

As to whether it's balanced, GURPS Psionic Powers briefly addresses limitations exceeding -80% (p. 19) and says the GM is free to reduce the cost more than usual if it seems appropriate. The example given is actually more generous than the OP method (-140% limitations reducing a 25-point advantage to a 1-point perk, where the OP method would only reduce it to 2 points), so the OP method is probably not too generous -- i.e., it's okay as a guideline for GMs.

[vierasmarius]

Originally Posted by munin

I'm sure this exact suggestion has popped up before on the forums (for both additive and multiplicative modifiers), and generally not been hated, but I can't find it. Bah.

Yeah, it's an idea I've had for long enough that I couldn't say whether it was originally my own. I was just reminded of it by one of the recent Powers threads.

As to whether it's balanced, GURPS Psionic Powers briefly addresses limitations exceeding -80% (p. 19) and says the GM is free to reduce the cost more than usual if it seems appropriate. The example given is actually more generous than the OP method (-140% limitations reducing a 25-point advantage to a 1-point perk, where the OP method would only reduce it to 2 points), so the OP method is probably not too generous -- i.e., it's okay as a guideline for GMs.

Ah, I wasn't aware of that note in Psi Powers. Very interesting... It probably is a good idea to have this option only available with GM oversight. In fact, Multiplicative modifiers in general may require more oversight than Additive.

[Blind Mapmaker]

If you use 20% base cost as a hard and fast minimum in all cases, it won't be too unbalanced, but that's basically giving your players extra points. As I see it, the increased final cost when using multiplicative modifiers is the price you pay for getting higher price breaks for the same limitation.

[Trachmyr]

This is the way I handle it... any limitations past -80% is applied against the enhancements directly, just as in Addative Modifiers. However, total "Enhancements" cannot be reduced to below 0%. Thus in the example of a 100pt ability with +100% in enhancement and -180% in limitations, would yield a 20pt ability. This allows Multiplicative modifiers to never give a "worse" value than the addative approach.

I could see an arguement to waive the "Enhancement can't be reduced below zero" clause, which would make the example come out to 16 points. But I leary of allowing advantages to be reduced to as little as 4% normal cost (or less) no matter how limited.

[Kuroshima]

Personally, I would ask for 5e to either go fully multiplicative (so +10%, +30%, +50%, -10%, -20% converts to 1.1*1.3*1.5*0.9*0.8=1.5444->+54.44%) [my choice] or it directly takes the Hero route (so it's one plus enhancements divided by 1 minus limitations, in the previous case, it becomes (1+0.1+0.3+0.5)/(1-(-0.1-0.2))=(1+0.8)/(1+0.3)=1.8/1.3=1.384615385->+38%) as the optional Multiplicative Modifiers rule.

I know both require that you grand your calculator, but really, you also need to do so with the current MM rule. Both produce fairer results than either current additive or multiplicative modifiers for traits with a lot of modifiers. Both allow for an infinite number of limitations, and add diminishing returns for limitations. Fully multiplicative also includes increasing returns for enhancements, and has the advantage that a -X% actually reduces the cost by -X% (Under the Hero route, a -50% limitation compensates a +50% enhancement exactly, but naked, it only reduces cost by 33%, since it becomes 1/(1+0.5)=1/1.5=2/3->-33.33333% limitation). It's also probably easier to understand.

[malloyd]

Eh, there are mathematically neater ways of doing this than GURPS or Hero uses, but I don't know that it matters much. All generic cost modifiers will yield ridiculous results, occasionally even if you are applying only one modifier. If you apply enough it makes a really large difference which system you use, the cost is about as likely to be ridiculous or unbalanced no matter which system you used.

In a lot of ways fuzzing up the system so all modifiers require a judgement call to determine their value in each case would be less prone to abuse than a more streamlined system. Or just offer them all as equally "official", situations where different schemes generate radically different costs just helps make it clear this isn't intended to substitute for good judgement.

[Joel]

Personally I always use multiplicative modifiers, and for limitations totaling more than 80% I subtract the limitation value exceeding that before multiplying by 0.2 for the last 80%, down to a minimum of 20% of the un-modified advantage.

So for an ability with +500% enhancements & -130% limitations that would be (1+(500-50)/100)*0.2 = 1.1 times base cost.

Edit: Looking through the thread more carefully, this works out exactly like Trachmyrs method (the only difference being between limiting to 100% of the original cost or more before multiplying by 0.2 or limiting to 20% or more of the original cost after multiplying).