For the point cost gurus: What's a fair cost for +/-1 to be hit?

[tbone]

A few years ago, another forumite and I had a conversation on setting a fair cost for a trait, and I said, "Hm, I think I'll ask the experts on the forum".

And then I promptly forgot to do so. But I guess the Cosmic GM has given me an IQ roll to remember. So:

The question concerns a fair character point cost for a +/-1 to be hit in combat, i.e., the cost of "foes take +/-1 to hit you" as a trait. (I'll call this "TBH", for "to be hit".)

A bit of preamble:


Some context

Yes, such a trait is obviously a component of SM, and its cost is most relevant within a discussion of pricing SM. But this trait could exist elsewhere – say, as a component of some supernatural blessing or curse that protects or hoses a character when attacked in combat.

If anyone does want to discuss cost of SM overall, I'd like to request that it be taken to its own thread, maybe one of several older threads on the topic. Cost of SM is a big topic covering a lot of tricky-to-price sub-components. I'd prefer to focus on TBH alone in this thread, without it getting buried and lost in a discussion of a dozen different things.


Some background talk

> I've seen past suggestions pegging -10 pts as a fair cost of +1 TBH (such as here). This could presumably be reversed to 10 pts for -1 TBH.

> My initial correspondent suggested the same numbers, following this approach:

• If you have -2 TBH, that's sort of equivalent in value to having +1 to all Active Defenses (as your foes would have to take -2 TH using Deceptive Attack to offset +1 AD).
• The value of +1 to all AD could be seen as about 20 pts (a lesser price than the sum of the costs of +1 to all individual defenses, yes, but reduced as typically only one AD is used vs an attack).
• If -2 TBH is arguably equal in value to +1 on all AD [20], then -1 TBH is worth [10]. By symmetry, +1 TBH would be worth [-10].

> In this post, in a discussion on cost of SM, Kromm suggests in passing that -5 pts for +1 TBH feels about right. (Maybe he'd also consider 5 pts as feeling right for -1 TBH; I don't know.)

> And FWIW, back in the 3e days, I guesstimated a fair cost for TBH (again, the context was cost of size) as follows:

• -10 pts per level for the first two +1 TBH, -5 pts per level for additional +1 TBH
• 10 pts per level for the first two -1 TBH, 5 pts per level for additional -1 TBH

But those numbers were based purely on "sounds right to me, I guess", not on any fancy calculating.


Okay, enough preamble!


The question(s)

Question 0: Is the cost of +/1 TBH already hashed out and satisfactorily answered in an old thread, in a Pyramid issue, etc.? If so, a pointer would be appreciated.

Otherwise:

Question 1: Regardless of cause, and regardless of type of attack (melee strike, ranged strike, grapple, etc.), what's a good way to calculate a fair cost for a generic +/-1 TBH?

And if there isn't a slick way to calculate it, what feels right?


What say ye, GURPS trait pricing gurus?

[Christopher R. Rice]

I asked Sean about this in email a while back and thought it was important enough to blog about (with his permission). Doesn't exactly answer your question - but it's got useful thoughts.

I think that something like Obscure Vision (Doesn't affect Area -50%; Defensive, +50%; Stealthy, +100%) [4/level] is pretty close. That's -1 to see and -1 to hit when using Vision as your targeting sense. Which is basically what low SM does.

[Varyon]

I previously put it at [+10] per +1. I worked this out as [5] for a Sneaky Talent and [5] for putting Cosmic on a half-level of Dodge* (to make it passive) for -1 SM, then simply reversed that for +1 SM. If you want it to only be a penalty to hit, not to actually see, then [5] would probably be sufficient.

*This should technically only be [3.75], as that's the increase you'd be looking at for +50% on something that has a base cost of [7.5]. But considering you still actually get to use an Active Defense in a situation where you'd normally be allowed to do so is probably worth an additional boost; arguably [5] undercharges a bit here, but I think it works.
This also technically means you're limited to inflicting a penalty of -2xDodge at worst with this pricing, but even for a character with average defenses that's a pretty hefty penalty.

Originally Posted by Christopher R. Rice

I think that something like Obscure Vision (Doesn't affect Area -50%; Defensive, +50%; Stealthy, +100%) [4/level] is pretty close. That's -1 to see and -1 to hit when using Vision as your targeting sense. Which is basically what low SM does.

Low SM still penalizes attacks when the attacker is relying on other senses than sight. Additionally, by default that would only work for those relying on light in the visible spectrum - against a foe with Multispectral Vision you'd at a minimum need Extended 2 (Infravision and Ultravision) +40%, or maybe Cosmic +50% to affect all light. RAW, that's probably something like [5] per -1 per affected sense, but personally I might be inclined to let you have your Obscure affect multiple senses at once with those beyond the first being at 1/5th cost; you'd probably end up somewhere around [10] per -1 (Vision [5] + Hearing [1] + Taste/Smell [1] + Touch [1] would cover mundane senses for [8]; if you allow a generic Detect that would be another [+1], but I'd be inclined to boost it to [+2] both because it covers so much and to adhere to GURPS' rampant pentaphilia). I think there's a Targeting Only Limitation in Psionic Powers that could be used to make it only a penalty to hit, not to detect, but personally I'd probably just halve the cost to [5] per -1 for that.

[PTTG]

Isn't this basically the same as an Enhanced Defense such as Enh. Dodge? It sounds more powerful than any one of those since it's always active. I'd say it's around [20] since it's quite a bit better than Dodge at [15].

[Varyon]

Originally Posted by PTTG

Isn't this basically the same as an Enhanced Defense such as Enh. Dodge? It sounds more powerful than any one of those since it's always active. I'd say it's around [20] since it's quite a bit better than Dodge at [15].

Cosmic +50% on Enhanced Dodge allows it to work against things that you normally cannot Dodge (sneak attacks, for example), which I feel is comparable to the passive effect you get from a penalty to hit. Of course, you have to buy it for your original Dodge first before you can apply it to Enhanced Dodge, where it costs [7.5] per level (because you're applying a +50% Enhancement to the "free" [15] worth of Dodge you already have), and until you have it for all of your Dodge you'd only have to pay this price for the passive effect. Every +1 to defense is equivalent to a -2 to hit, so the price for -1 to hit would be half this, or [3.75]. As I noted, rounding this up to [5] helps account for the fact that you actually still get a normal Dodge (or other defense) against normal attacks (it probably undercharges, but [10] would probably overcharge, so I think going with [5] should work alright).

[Anthony]

The answer to this is "define fair cost". However, in mechanical terms, given that deceptive and telegraphic attack exist, -2 to be hit is equivalent to +1 to all active defenses that still has (very limited) effect when unable to take active defenses, but does not work for using retreating dodge to get out of an area effect, so the point value per -1 should be between [10] and [15].

Note that SM is very messy trait with a huge number of effects that probably shouldn't have a cost of [0], though there are ways to adjust it to make that cost appropriate.

[pawsplay]

I think it's probably [20] because one of the most common effects is going to be to lower opponent skill down the 8-12 range "hump."

[Kallatari]

I don't remember how I came up with this value - and I maybe even stole it from your 3E GULLIVERS - but since shortly after GURPS 4E has been out I've used a house rule with SM costs +/- (10 x level). It also removed the size-limitation discount to ST (so everyone pays the same cost for the same ST, regardless of SM). I find that it feels even more fair since I started using the log ST introduced in Know Your Own Strength.

So, while I can't pinpoint how that's fair or exactly how I built it, having played that way for years, I think it definitely "feels right." (otherwise, I would have kept tweaking it).

However, as others have pointed out, a +/-1 to SM is not exactly the same as a +/-1 TBH. If I had to deconstruct that, well, increasing SM gives the following main effects:

- easier to see
- easier to hit
- extended reach
- more mass (mass-based HP/ST, for things like collisions)

So, two benefits and one drawback, that combined equal to what I priced as -10 points. So the "easier to hit" has to be a greater disadvantage than -10 points if needs to counter the values of extended reach and more mass and end up with a final combined value of -10 points.

Now, I have another houserule trait I call "Passive Defense" which is specifically a -1 to be hit, and I priced that at 25 points per level. I think I created this for things like "mobile cover" that get in the way that isn't really darkness or DR. Again, not sure how exactly I got it, but if we plug that into my SM equation value, I probably made extended reach, extra mass , and easier to see were worth 15 points combined (or -15 points for SM -1) and then you add the 25-point Passive Defense to get the final total of 10 points for SM -1. While I don't specifically have a reverse of Passive Defense to make you easier to hit, I think the logic would fit that I probably valued as being worth -25 points when I created SM.

So throwing out a number of +/-25 points for your consideration. Looking at it, it sounds like a lot. But as someone else mentioned, against mundane, ordinary folks, these are the modifiers that hit them in the 8-12 range that has the most effect. So maybe it should be worth a lot.

But I'll also acknowledge it is a significant difference from building something with Obscure to only give a penalty to hit. I think the build Christopher suggested isn't perfect, but no amount of change that I add would ever get that to go as high as 25 points. So clearly a valid argument that it should be worth less than 25 points as well.

So, this post is a bit more of a "here's how I do it" as opposed to a concrete solution to your question (especially since I don't remember all of my original assumptions). But I hope it's helpful in the discussion anyway.

[Kallatari]

Originally Posted by Christopher R. Rice

Obscure Vision (Doesn't affect Area -50%; Defensive, +50%; Stealthy, +100%) [4/level]

If trying to duplicate SM, I'd make a few more changes to that build.

First, it should be Always On, which if memory serves is a special case worth -50% for Obscure (but I could be wrong; don't have books with me).

As Varyon pointed out, it needs to have Extended to cover more than just ordinary vision. Beyond what Varyon said, it also has to block all forms of Scanning Senses: radar, ladar, sonar, etc., all of which are affected by that subject's SM. Each one would require its own Obscure. You should in theory Link them, but since they're Always On, that can probably be skipped.

Instead of purchasing dozens of them, I'd be willing to roll them all into a single Cosmic, Extended, all senses impacted by SM, +300%. I'm pretty sure +300% is a RAW price for a cosmic that represents "all variants thereof" in some broad category (again, don't have books on hand).

So, i suspect it would be something closer to:

Obscure Vision (Always On, -50%; Cosmic, Extended, All senses impacted by SM, +300%; Doesn't affect Area -50%; Defensive, +50%; Stealthy, +100%) [9/level]

So now we're closer to -10 per level of SM using this build to ballpark it.

Side question. Is Doesn't Affect Area for Obscure really worth -50%? I could have sworn I've seen it somewhere as being worth significantly less. If it is worth less, that would actually round up the final value to 10 x level. Ditto if my Always On for Obscure that I'm pricing by memory is worth less than -50% as well.


(Per my previous post, I wonder if this is how I determined the cost of my houserule SM at 10 points per level long ago. Oh well, it will just have to remain one of the unsolvable mysteries of the world, I guess. ;) )

[Varyon]

For SM specifically, my most recent breakdown of that is as follows. For high SM, the boost to Reach, Trampling, Evasion, etc is worth roughly [5] per +1, as adding Switchable +10% to it would basically give you Stretching [6] (technically that would be [5.5], but close enough); this is reversed to [-5] per -1 for low SM. The change to how difficult you are to detect and hit I consider to be worth [10] per -1, [-10] per +1, as explained upthread. The built-in poison resistance of high SM (you require more poison to affect) is worth [2] per +1 SM, and the boost to Intimidation is worth [3] per +1 SM; these get reversed to [-2] and [-3] for low SM. All this works out to a Feature.

... but then we get into the other effects. The bonus to grappling is probably worth [2] per +1 SM ([-2] per -1 SM) if just using the rules from Basic Set, but it gets a bit more complicated if using the weight-as-proxy rules from Technical Grappling. That puts high SM in the lead... but then we get to the issue of gear, supplies, life support, etc. I approximated this by calculating how many points in Lifting ST (Gear Only -20%) are needed to make an otherwise-ST 10 person as encumbered by appropriately-sized gear as they would be if SM 0, and then doubled this value to account for the fact there is a similar increase to price. This varies by SM (there's no simple [n]/level here), and works out to [-5*((M*100)^(1/2)-10)], where M is the multiplier to the SM-based weight multiplier. This is [-25] for +1 to SM (due to the x2.25 multiplier), [-50] for +2 to SM (x4), [-100] for +3 (x9), etc. For low SM, the same equation works, and you wind up with [15] for SM -1 (x0.49), [25] for SM -2 (x0.25), [35] for SM -3 (x0.09), etc.

Overwhelmingly, high SM is a Disadvantage while low SM is an Advantage (although high SM is more disadvantageous than low SM is advantageous - SM +6 would be [12] for the grappling bonus and [-450] for the increase to weight and cost due to everything being 100x heavier and more expensive, while SM -6 would be [-12] for the grappling penalty and [45] for everything being 1% as heavy and expensive). Using the ST discount, SM +1 balances out if you buy 23 levels of ST (total ST 33), SM +2 also balances out with ST +23 (total ST 33), SM +3 balances out at ST +32 (total ST 42), SM +4 balances out at ST +48 (total 58), etc. But it's far too complicated to just assign a per-SM price...