Off-Hand THAc0

Giant2005

I have been mucking about with the editor comparing end-game builds (In this case Kensai/Thief vs Swash/Cleric), and one thing I noticed is that I have no idea how the hell Off-Hand THAC0 is calculated.

With 3 pips in Two-Weapon Style and a cloak that reduces Off-Hand THAC0 by 2, in theory both the main-hand and off-hand weapons should share the same THAC0. However the fully equipped 24 Kensai/28 Thief had a 13 point difference in THAC0 between his main and off-hand and the 25 Swash/28 Cleric had a 6 point difference in THAC0 between his main and off-hand.
In the Fighter' case, 3 points of that difference can be accounted for via the difference in weapon enchantments and the same can be said of 1 point of the Cleric's. However, I have no idea where the rest of the difference is coming from.
The gear isn't relevant as I watched the THAC0 of both weapons change appropriately as each item was equipped. Something within the characters themselves explains the disparity.

Caeria

Well, I just ran a test with both the characters you described as kitted, and I didn't have any problems. The off-hand THAC0 was calculated exactly as it should be. The main-hand THAC0 and off-hand THAC0 were exactly the same, barring the differences in item enchantment/elf bonuses.

I can't figure out what your problem would be, that you're having such discrepancies. Do you have any mods installed?

Giant2005

No mods but it is strange that it happened to me and not to you. Something which might account for the difference was that the Kensai/Thief had 25 Str and the Swash/Cleric had cast all of his self-only buffs and resulted in 24 Str (Plus the effects of all of the buffs).

I'm pretty sure the equipment isn't a factor as I watched it modify the THAC0 as it should, but I'll list it anyway just in case I missed something:

Belt of Inertial Barrier
Helm of Balduran
Gloves of Extraordinary Specialization
Amulet of the Master Harper
Ring of Gaxx
Ring of Earth Control
Belm (Off-Hand for both)
Shuruppak's Plate
Scarlet Ninja-To (Main-Hand for Swash/Cleric)
Club of Detonation +5 (Main-Hand for Kensai/Thief)
Montolio's Cloak

Caeria

Hmm...I know for sure after checking NI that the gloves and the helm increase THAC0 for both, and the cloak should even things out with the off-hand, like you mentioned. None of the other items should affect THAC0.

I can't promise I can help, but maybe upload your character file and let me take a look at it?

Giant2005

I deleted it already but I can make another. I'm just not sure if I can actually upload it - that hasn't worked for me in the past.

Caeria

You have to zip things up to upload them

Giant2005

Wow! That is some seriously helpful stuff right there! Until now I had been thinking that I was too new to these forums or hadn't made enough posts to earn the right to upload files or something.

As for the guy himself, I don't really know wtf is going on. Even when completely naked just putting a weapon in his off-hand shows an off-hand THAC0 well below the empty main-hand. I don't really recall at what moments the Specializations were taken but maybe the Dual-Classed Fighter thing isn't working as well as it seems to. I might have taken Grand Mastery as a Thief without the Grand Mastery actually counting for anything. Although on second thoughts, that probably isn't the case as I was witnessing similar effects although on a smaller scale with the Swash/Cleric dual-class and that doesn't even have Grand Mastery.

Pantalion

Considering you get 1 attack offhand versus 4 attacks main, and generally the best offhand weapons are things like Crom Faeyr and Kundane, neither of which are necessary for their damage, I can't say I've ever taken much notice of off-hand THAC0 in the first place. For the Kensai/Thief, do you have Grand Mastery in scimitars as well as clubs?

Caeria

After taking a look at your save, I am thoroughly confused. It's showing up as -25 on the main-hand and -22 on the off-hand, which is exactly what it should be. Are you getting something else?

Giant2005

Weird. I am getting -25 and -12. Here is an image of what I see:

And Pantalion, I agree - the Off-hand weapon is largely irrelevant. I just noticed the different values and was curious as to how off-hand THAC0 was calculated as I couldn't figure it out. Although now it seems that that curiosity was pointless as Off-Hand THAC0 is calculated the same as the main-hand. It is just that something weird is going on with me.

Caeria

Well if that isn't the darndest thing. I've never tried messing around with THAC0, so I don't even know where to being trying to figure out what went wrong.

Pantalion

Giant2005 said:

It is just that something weird is going on with me.

Well, I don't think I've ever had a game of BG2 where some weird, non-replicable bug didn't happen to me. All I can suggest is trying two unenchanted clubs and looking carefully through the list of THAC0 modifiers to see if something isn't being accounted for on your offhand.

Giant2005

Pantalion said:

Giant2005 said:

It is just that something weird is going on with me.

Well, I don't think I've ever had a game of BG2 where some weird, non-replicable bug didn't happen to me. All I can suggest is trying two unenchanted clubs and looking carefully through the list of THAC0 modifiers to see if something isn't being accounted for on your offhand.

I'm not sure I care enough any more to be honest. Learning how THAC0 works is interesting but if it is an isolated event that only applies to me then I don't really care. I don't need or even really want my off-hand THAC0 and something unique to me that I don't care about isn't worth investigating.

What is kind of interesting though is that I have Haer'Daelis Dual-Wielding too and his off-hand THAC0 is just fine.

MrNooby

For me, I'd have to keep looking into it until I found what was causing it, or it would drive me crazy.

And in the end, it'll be like that missing HP thing, where the problem is right in front of me, and makes me feel like an idiot :P

Lord_Tansheron

Pantalion said:

Considering you get 1 attack offhand versus 4 attacks main, and generally the best offhand weapons are things like Crom Faeyr and Kundane, neither of which are necessary for their damage

Would just like to say here that Crom Faeyr actually does decent damage, certainly on another level from Kundane, Belm, and SNT, which really are very underwhelming in their damage.

EXTRA: How to tell if it's better to use Crom Faeyr in the offhand or an APR weapon (assuming you don't want to pair CF + APR in the first place which is probably best)

APR = your total APR *without* an APR offhand
CFstr = the damage bonus you get from CF's 25 STR; this depends on how much STR you have without it
AVGmh = average damage of your main hand weapon, per hit (no bonuses, just pure weapon damage including procs)
APRbon = the amount of bonus APR you get from the APR offhand (usually 1)

Using those variables, we can calculate what would be needed for both variants (CF oh vs. APR oh) to break even:

APR*CFstr = AVGmh*APRbon

This can then be transformed to allow us to solve for the variable we'd like to look at:

AVGmh = (APR*CFstr)/APRbon

-> this tells you how much average main hand damage you'd need to do at least as much damage with a given APR bonus as you would with Crom Faeyr in the offhand

APRbon = (APR*CFstr)/AVGmh

-> this tells you how much APR bonus you would need to deal at least as much damage with a given main hand as with Crom Faeyr

EXAMPLE 1:

Foebane+5 as main hand; 13+ Fighter with Grand Mastery and 19 STR

APR = 4
CFstr = 7 [for 19->25 STR]
AVGmh = 12.5 [2d4+5+1d4]

How much APR bonus would we need for APR oh to be > CF oh?

APRbon = (APR*CFstr)/AVGmh

-> APRbon = (4*7)/12.5 = 2.24

Oh dear! The best APR offhand is only +1, meaning it's better to use Crom Faeyr!

EXAMPLE 2:

Kundane as offhand; 13+ Fighter with Grand Mastery and 22 STR

APR = 4
CFstr = 4 [for 22->25 STR]
APRbon = 1

How much average damage per hit would a main hand need to do so that APR oh > CF oh?

AVGmh = (APR*CFstr)/APRbon

-> AVGmh = (4*4)/1 = 16

Quite a lot! Is there a weapon with that much damage? The highest-damage mainhand (unmodded) is Flail of Ages+5, which does 19.5 average damage per hit (1d6+6+2+2+2+2+2) - yep, that's more! But that's no surprise, after all we've given this to a character already at 22 STR; this would usually be the one with the Girdle of Fire Giant Strength, or a CHARNAME loaded with STR bonuses (many people like to do that).


CONCLUSION: Crom Faeyr is an amazing offhand, for everyone except those with already very high STR.

CAVEAT: Crom Faeyr + APR offhand itself is still the best option, as CF actually has great damage main hand damage (2d4+3+5 = 13 average; more than Foebane+5). Also, THAC0 has been disregarded in this calculation, but can be VERY relevant in many scenarios; this gives a big advantage to CF as well, since STR increases melee THAC0.

AND AS ALWAYS: Individual setups make for HUGE differences! Always think about your own situation, and what variables are involved how. This is intended as a rough guideline to help you figure out your own personal puzzle.

Gotural

Kensai and Swashbuckler THAC0 bonuses don't apply to the off-hand, hence the bigger difference for the Kensai 24 than for the Swash 25.

MrNooby

Gotural said:

Kensai and Swashbuckler THAC0 bonuses don't apply to the off-hand, hence the bigger difference for the Kensai 24 than for the Swash 25.

Except that two people are getting two different results on the same character :P

Giant2005

Gotural said:

Kensai and Swashbuckler THAC0 bonuses don't apply to the off-hand, hence the bigger difference for the Kensai 24 than for the Swash 25.

I thought that might be it but it doesn't really add up. Look at that screenshot I posted earlier - 3 points of the deficit is due to the difference in the main-hand's +5 weapon and the off-hand's +2 weapon, but that still leaves 10 unexplained points. The Kensai class gives an 8 point bonus which isn't enough to explain it unless there was another 2 point factor somewhere?
Also Caeria had it working fine over there so obviously the Kensai bonus was being applied to the off-hand in that instance.

Gotural

I can't look at your screenshot on my phone but if you have GM (at least Mastery in fact) in your main hand and only specialization in off-hand it will explain the 2 points difference.

Gotural

Your Swash/Cleric has a 6 points difference : 5 from being a level 25 Swashbuckler, and the last one from the weapon enchantment level.

Giant2005

You might be on to something there. The math works out for the Swash/Cleric but not so much the Kensai/Thief as both weapons have Grand Mastery. However I am not sure when exactly those specialization points were taken - it may have only had specialization in Scimitars (The off-hand weapon) prior to unlocking the Kensai levels and the extra pips placed in with Thief levels may not have actually done anything.