Follow along with the video below to see how to install our site as a web app on your home screen.
Note: This feature may not be available in some browsers.
Welcome to rpgcodex.net, a site dedicated to discussing computer based role-playing games in a free and open fashion. We're less strict than other forums, but please refer to the rules.
"This message is awaiting moderator approval": All new users must pass through our moderation queue before they will be able to post normally. Until your account has "passed" your posts will only be visible to yourself (and moderators) until they are approved. Give us a week to get around to approving / deleting / ignoring your mundane opinion on crap before hassling us about it. Once you have passed the moderation period (think of it as a test), you will be able to post normally, just like all the other retards.
Note: Let me know if I have forgotten any factor in the formulas.
All right then, here are the calculations for attacking the Astradaemon in Vordakai's Tomb with Octavia. I have assumed a lvl12 Octavia with DEX bonus +4, while for the Astradaemon I have assumed the following stats: https://pathfinderkingmaker.gamepedia.com/Astradaemon
For Octavia I have assumed a build of Rogue1/Wiz3/AT8
I have assumed that she has taken the feats Accomplished Sneak Attacker, Point Blank Shot, Precise Shot, Weapon Focus(Ray), which are core to her job. At lvl12, this leaves a maximum of 2 available feats for Penetration.
Main Premise:
Your single-target attacks need to overcome 2 obstacles in order to hit: They will need to overcome the Astradaemon's Touch AC and they will also need to overcome the Astradaemon's considerable SR. So we need to calculate probabilities for 2 different things and combine them in order to find out our overall probability of success.
Step A: Overcome Touch AC
Main formula: BAB+1d20+DEX+Other >= 19 in order to hit
For BAB=5, DEX=4, and assuming Point Blank Shot, Precise Shot, and Weapon Focus(Ray) have been taken (ie, Other = +2), this translates to 1d20>=8.
Therefore, you have 65% to hit and 35% to miss.
For spellcaster level 12, this translates to
1d20 >= 15 – Bonuses,
where Bonuses is the potential bonus from up to two Spell Penetration feats.
Case A: No Penetration feats
1d20>=15, ie 30% to hit and 70% to miss
Case B: Spell Penetration
1d20>=13, ie 40% to hit and 60% to miss
Case C: Greater Spell Penetration
1d20>=11, ie 50% to hit and 50% to miss
Step 3: Combining Step A and Step B
Case A: No Spell Penetration feat:
0.65*0.30 = ~20% to hit and 80% to miss
Case B: Spell Penetration feat:
0.65*0.40 = 26% to hit and 74% to miss
Note that this result means that you still have ~55% chance to miss 2 in a row, ~40% chance to miss 3 in a row, and ~30% chance to miss 4 in a row.
Case C: Greater Spell Penetration feat:
0.65*0.5 = ~33% to hit and 67% to miss
Note that this result means that you still have ~45% chance to miss 2 in a row, ~30% chance to miss 3 in a row, and 20% chance to miss 4 in a row.
Conclusion:
I will let you guys scrutinize my post for objections and mistakes.
As things stand, my conclusion is what I have been saying all along.
PS. Thanks Xamenos for the correction to a calculation.
Hopefully the post above has answered your question. The main thing I am trying to show you guys is that you cannot depend on penetration against opponents with high SR, Penetration feats or not. You need a backup plan. And since you need a backup plan anyway, the penetration feats are not very important.
Well, I will let people smarter than I to discuss, but I wonder: doesn't the event "SR penetrated on the premise that touch attack was successful" follow the rules of conditional probability instead of the probability of 2 completely independent events?
In that case, instead of overcoming Touch AC you will have to overcome one of the saving throws. So the logic is similar, and you still have to combine the probability of success for overcoming SR with the probability of success for overcoming the saving throw, ie it is not going to be easy.
Depending on how high the related saving through is in comparison to the Touch AC, you may or may not have a better chance.
So I generally suggest that you keep your spells for where they are going to work. Ie, opponents with insignificant SR and some low saving throw (or low Touch AC) that you can exploit.
I wonder: doesn't the event "SR penetrated on the premise that touch attack was successful" follow the rules of conditional probability instead of the probability of 2 completely independent events?
Well, I will let people smarter than I to discuss, but I wonder: doesn't the event "SR penetrated on the premise that touch attack was successful" follow the rules of conditional probability instead of the probability of 2 completely independent events?
For BAB=5, DEX=4, and assuming Point Blank Shot, Precise Shot, and Weapon Focus(Ray) have been taken (ie, Other can easily go up to +20 and higher if you really want it), this translates to 1d20>=1.
Therefore, you have 65% 95% to hit and 35% 5% to miss if you really want it.
Step B: Overcome SR
No Penetration feats:
1d20>=13, ie 40% to hit and 60% to miss
Greater Spell Penetration:
1d20>=9, ie 60% to hit and 40% to miss
Therefore, Greater Spell Penetration provides 150% multiplier to base chance to overcome SR in this particular case.
Step 3: Combining Step A and Step B
...is not needed Because step A is completely irrelevant to discussion about spell penetration, only step B matters
Conclusion(Trashos):
...my conclusion is what I have been saying all along (SP is not very important).
Correct Conclusion:
Greater Spell Penetration provides 20% flat bonus or 150% multiplier to base chance to overcome SR in this particular case.
Which roughly means 3 connected spells instead of 2 for 5 attempts in this particular case. Or roughly33%more damage in this particular case.
Whether this worth 2 feats or not is up to you to decide.
panda well, you have illustrated that it is much easier to increase attack by buffs and / or decrease AC by debuffs than decrease SR. This is correct. But this is not the point.
Hopefully the post above has answered your question. The main thing I am trying to show you guys is that you cannot depend on penetration against opponents with high SR, Penetration feats or not. You need a backup plan. And since you need a backup plan anyway, the penetration feats are not very important.
Not everyone boycotts bards and buffs like you do Trash. Yeah, if you can’t hit the broadside of a barn you’re correct that Spell Pen ain’t helping you. Of course you can also use non-ray spells if that’s the case.
And if your action economy plan is being a caster in the hardest fights (the reason people play pure casters) then you leave no stone unturned to beat those saves. Saying Spell Pen sux because you can’t beat the saves anyway just means you don’t have any experience playing a full caster.
I'm not sure if calculating in the ability to overcome touch AC or saving throws is a good idea. Co-mingling them skews the results and requires too many assumptions. An Eldritch Knight is going to have a very different chance to land that touch attack. The variance is also large if you're attacking its Fortitude (12) instead of Reflex (17). Too many assumptions, too many variables. I really understand their inclusion, but it's a separate argument that has to be built of the SR question first.
SR 27 - 13 CL = 14
35% chance to overcome spell resistance with no Spell Penetration (45% with Elf)
45% chance to overcome spell resistance with Spell Penetration (55% with Elf)
55% chance to overcome spell resistance with Greater Spell Penetration (65% with Elf)
As a +4 bonus in a D20 game would suggest, it increases your probability to overcome SR by 20% in a singular instance. The arithmetic is pretty simple, and positive. You go from a 1/3 chance to a 1/2 chance. Too bad all the significant considerations are rational, rather than mathematical.
As Trashos points out, The enemies with high SR are not common. There are a wealth of options to deal with them (this is a party game), and many potent spells ignore SR or demand repeated checks which dramatically. PFKM also has significant bloat, so your odds of overcoming saves may already be marginal, in which case relying on an offensive spell is not practical anyway. Ultimately in Kingmaker, I end up taking them around Level 10 because I've already selected most important feats by that time, and the alternatives are few. The marginal improvement in success rate of spells I do use is greater than alternatives. This changes if you're not a pure caster arcane caster though.
My conclusions:
Full Arcane Caster: Greater Spell Penetration, by virtue of poor alternatives and action economy dependent on offensive spells.
Full Divine Caster: Not worth it, unless they are your only full caster.
Full Bard: Worth it if support. Not worth it if mixes in melee.
Gish or Multi-class: Not worth it.
Party has a Mystic Theurge + other spellcaster: Not worth it (use teamwork feat)
Conditionals don't make for a satisfying conclusion, but that's my take anyway.
“As a +4 bonus in a D20 game would suggest, it increases your probability to overcome SR by 20% in a singular instance.”
No, that isn’t how the math works. In your case your probability is increased 11/7 which is quite a bit more than 6/5 (20% increase). It’s a roughly 57% increase.
Now to Trashos’ point if that only gets you a bite at an apple you’re missing half the time on the backend then maybe you’re better off fighting with weapons (my thing) but there are several casters here who can fill you in on how to do much better than that.
They all bring the Spell Pen to maximize the chance to show their big DC/damage skillZ.
You do know that saving throws don't usually negate damage entirely, right? Even if something gets their reflex save they still take half the fireball, which is probably more damage than anything your caster could be doing with a weapon. Sirocco fails to knock them over but still does damage every round, etc
Or, hell, just spam magic missile. Give your wizard the magic missile amulet and just fill your whole spellbook with them if you like. No more caring about AC and saves for you!
We are not supposed to have a Paladin. To my horror, no Jubilost either. But your point is exactly one of my points, in Pathfinder we are generally supposed to attack opponents where it hurts, and this is not what we are doing in our example.
You do know that saving throws don't usually negate damage entirely, right? Even if something gets their reflex save they still take half the fireball, which is probably more damage than anything your caster could be doing with a weapon. Sirocco only fails to knock them over, etc.
Whenever I ever get finished with the Wrath playthrough I've just switched to pure caster Octavia in my current P:K run. She gets an extra +4 Spell Pen from the Ruin Quarterstaff and another +2 from something else. She's getting awfully close to SR being the weak point that she does attack.
This is what a full caster looks like. (Not my shot)
