Gurps, question about FP cost for Psionics

[Not another shrubbery]

PK Shield uses the -10% version of Requires (Attribute) roll. For defenses, that means you roll each time the defense would apply to an attack, or once per minute for constant exposure..

[Plane]

The "passive" nature of PK shield is important because of P56:

Active uses are always detectable with vision, hearing, touch, and/or smell, while passive uses are only discernable using special senses.

I expect that even if a Force Field is normally invisible, you might have some hint one was there if you noticed a bullet heading for someone's eye and then just bounce off it instead of penetrating the eye...

Not entirely sure though because bullets move pretty fast so you might just assume the bullet missed if you failed a perception roll.

Originally Posted by Anaraxes

But I don't see a reason from the stat block for it to work as described (rolling for each attack). "Requires IQ Roll" would normally just add a one-time activation roll.

PP56 is even more special since it initially says with PK Shield you roll IQ once per attack, but then follows up with saying you can roll once per minute if under constant attack...

Originally Posted by Anaraxes

After writing the previous post, I went back to check the pricing, thinking that maybe it was assuming a Power Defense. But it's a net -20% for 4 CP per point of DR, so there's no doubling of the DR for making that roll each attack hiding in there.

I don't think the option to do a Power Defence is actually coded as a modifier, it's just an option you can do with any power...

Since this is DR it requires me to check the Power Block rules...

Huh... I think maybe I misremembered how useful it could be. One of the requirements is:

The attack is Affliction or Innate Attack, the defensive ability is a form
of Damage Resistance that’s effective against the attack,

Actual weapons like bullets aren't TECHNICALLY innate attacks, but I guess I just assumed since there's situations of statting them up like Innate Attacks w/ Gadgets (done elsewhere in Powers) that it would be okay to Power Block against them...

Then there's the 2nd followup requirement:

and the two abilities belong to powers that either have the same focus or are opposed.

This one's a bit more flexible due to the followup disclaimer though:

the GM is free to waive the restrictions on focus.

Without a focus-restriction, presumably the attack doesn't need to be a power at all? Not sure.

PP8's writeup of the "Power Defence" rules don't seem as specific, they just talk about working against an "attack" (doesn't seem to require it to be an attack from a Power or an Innate Attack)

Originally Posted by DangerousThing

The example on p. 9 of GURPS Psionic Powers specifically states that PK Shield can be used in a Power Defense.

Nice find! More importantly, James uses it against BULLETS so we know that PP9's rules apply to weapons, not just attacks-from-powers as P168 seems to state.

Originally Posted by Anaraxes

Unfortunately Example James fails his roll, and according to the example, he gets 0 PK Shield Defense.

It's not getting doubled for making a Power Defense roll; it's just getting enabled, so it doesn't shed a lot of light on the "gets double it's usual DR" line.

The preceding page says "For a defensive advantage, success doubles the benefits from the ability" so I think that's the outcome we're meant to expect from James.

PK Shield was already enabled (it is passive) but he was risking it being disabled (which is what happened, since he failed the roll) by actively trying to double it from PK Shield 10 to effectively PK Shield 20

Originally Posted by Anaraxes

The Required IQ Roll Limitation is presumably the "Active Defense" form; the stats block uses the -10% value,

Requires IQ roll is inherently a -10% value, "Active Defense" is a -40% limitation according to pg 112 of GURPS Powers, and it is a DX-based roll...

We probably should have variants of the Active Defence limitation based on other attributes.

Originally Posted by Anaraxes

and it's Forcefield DR, so that's an available option.

What is? I'm not sure what special option would only exist for DR w/ Force Field enhancement....

Ah I think I know what you're referring to:

version of this limitation exists for the defensive traits listed under Force Field

That version is explicitly DX-based and worth -40% and PK Shield's under-hood pricing doesn't incorporate that version.

Originally Posted by Anaraxes

This means to me that the PK Shield isn't a Power Block in the "A
defensive ability gets double its usual DR" sense described on Powers p168. (Doubling 0 DR would still be zero; this defense just creates the base DR in the first place.)

You're not doubling 0 DR, James has a basic DR of 10, doubling would make it 20.

Originally Posted by Anaraxes

While I'm looking at Requires (Attribute) Roll, the description of that form says "Your ability only protects you against threats you’re aware of – and only if you make a roll to interpose it in time."

That's the 3rd-paragraph description (P112) of how the -40% DX-based variant works, not the description of how the -5% (Per/Will) or -10% (IQ/HT/DX) baseline versions work.

Originally Posted by Anaraxes

PK Shield certainly isn't up all the time

I think it actually might be, since it's explicitly "passive" per PP56...

Unless perhaps "this" refers not to the ability as a whole, but rather a "passive use" of it once it is switched on?

P236 glossary for passive:

An ability that applies constantly or activates in response
to a stimulus without any input from the owner. The GM makes all required die rolls.

P153 purple box:

A passive ability has effects that apply constantly, or that activate
without the owner’s input in a specific situation. If it requires a die roll,
the owner or the GM must roll – there’s no opting out.

This says "the Active Defense limitation shifts Damage Resistance from passive to active" but doesn't clarify if "requires DX roll" or "requires IQ roll" does that also.

The last paragraph I think is clear here:

"The same ability can have both passive and active aspects"
"turning on a switchable ability counts as an active use, even if the ensuing effects are passive"
"Unlike the ongoing, passive effects of such abilities, these active efforts can trigger sensors or abilities sensitive to active abilities – if only momentarily."

P153 includes 3 strict requirements for "Always On", the 3rd of which is:

3. The ability has none of these modifiers: Active Defense, All-Out,
Emergencies Only, Fickle, Reflexive, Requires (Attribute Roll), Requires Concentrate or Ready, Switchable, Trigger, Unreliable, or Usually On.

So we know that PK Shield is not "always on" but the issue here is what other category it falls into: Switchable or Transient.

Requires (Attribute Roll) isn't mentioned under the list of modifiers for either category so I'm not sure how to take it... especially since two different ways of applying it (roll once per minute or roll once per attack) is proposed.

Requires (Attribute Roll) is derived from "Unreliable" so a similar question applies on how to treat Unreliable DR in terms of whether it's always on or not.

Originally Posted by Not another shrubbery

PK Shield uses the -10% version of Requires (Attribute) roll. For defenses, that means you roll each time the defense would apply to an attack, or once per minute for constant exposure..

Those 2 approaches are so many worlds apart :/

[Anaraxes]

Originally Posted by Plane

Requires IQ roll is inherently a -10% value, "Active Defense" is a -40% limitation

Ah. That's where I was leading myself astray (not actually making it all the way to the end of that final paragraph, but assuming that normal activation and Active Defense were the -5% and -10% forms). Thanks for straightening me out there.