THAC0 calculated wrong
DemiGoth
Member Posts: 44
I was wondering if THAC0 was calculated right. My main char (mage/thief) walking around with high DEX and protected by the armor spell (comes down to an AC of 2) gets hit awfully much. So I toggled the attack info and here's what I found:
"Minsc - Attack roll: 16+7=23 HIT"
This is not right when I look at the PHB page 119 (revised edition):
"...THAC0 is modified by weapon bonuses, Strength bonuses, and the like. Figure Strength and weapon modifiers, subtract the total from the THAC0..."
This would mean that Minsc's attack roll would be 16-7=9. Hold this against a kobolt (AC10 iirc), the minimum he needs to roll is his THAC0 minus the kobolt's AC (13-10) is 3.
I know, it's still a hit, but the math behind the calculation is done wrong. Can the DEVs please comment on how the THAC0 is handled in BGEE? I figure that some sort of D&D3.x rule is implemented here and I fear it's done the wrong way around when still using AD&D2 AC values
"Minsc - Attack roll: 16+7=23 HIT"
This is not right when I look at the PHB page 119 (revised edition):
"...THAC0 is modified by weapon bonuses, Strength bonuses, and the like. Figure Strength and weapon modifiers, subtract the total from the THAC0..."
This would mean that Minsc's attack roll would be 16-7=9. Hold this against a kobolt (AC10 iirc), the minimum he needs to roll is his THAC0 minus the kobolt's AC (13-10) is 3.
I know, it's still a hit, but the math behind the calculation is done wrong. Can the DEVs please comment on how the THAC0 is handled in BGEE? I figure that some sort of D&D3.x rule is implemented here and I fear it's done the wrong way around when still using AD&D2 AC values
Post edited by Coriander on
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Comments
Jahiera has a base THAC0 of 19 using a sling+1 (in which she has a proficiency, making her THAC0 18). The hurls her sling to the kobolt (just checked the MM, AC 7(10), meaning 10 unarmored and 7 when wearing armor. The kobolts in the Naskel mines are unarmored). Following the above example of how AD&D2 calculates THAC0, Jahiera should roll (18-10=)8. She rolls 9 and BGEE tells me she misses..?
When determining a to-hit roll, the game generates a random number between 1-20. The game then ADDS any bonuses the character has to-hit. As per your Jaheira example, lets assume she's level 1. This gives her a base Thac0 of 20. Her +1 Sling and weapon proficiency give her a total bonus of +2 to-hit. This means she has a MODIFIED thac0 of 18, but her base Thac0 is still 20. On her character screen the game will display her modified thac0, but in the to-hit window it doesn't necessarily do that.
When calculating whether Jaheira hits then, the game generates a number between 1-20 and then adds 2. So if Jaheira rolls a 9+2, her result is an 11. With a base thac0 of 20, an 11 hits AC 9, which is insufficient to hit a kobold (AC 7).
The manual is misleading because it tells you how to determine your characters MODIFIED thac0, whereas the feedback window in game modifies your attack roll and then uses your BASE thac0 to determine whether you hit (which is confusing.)
Sorry if I was re-explaining things you already know about thac0, but I don't want to make assumptions.
What @nietzschelives says is correct. Bonus to hit can either be interpreted as lowering your THAC0 or increasing your attack roll. Lets say you have a base THAC0 of 10, a bonus of 3 to hit, and you're attacking an opponent with AC 0. You can either see this as: I have an effective THAC0 of 7, meaning I have to roll 7 or higher to hit this opponent or; I have a THAC0 of 10 meaning my total hit roll must be 10 or higher, and since I gain +3 to hit, i only need to roll a 7 on the D20 roll.
As far as I know Thac0 calculations are correct, but the feedback is definitely a little wonky.