Why THAC0 Rocks

[Mercule]

I've been running 1e for 25-odd years and still haven't figured out THAC0. To me, it just adds an unnecessary layer of complication

Generally agree. While I've been playing 3e for most of its life, I've been playing D&D in some form since the early 1980s. I found THAC0 to be a lousy, cluttering addition to 2e or late 1e. I've never seen it's advantage, from either side of the screen, and the repeating 20s make the math more difficult than it is usually portrayed. I've always used a DM screen, so I always have the attack tables in front of me -- which results in me actually being quicker at finding a hit/miss than any player has ever done the math for me. Sure, the 2e character sheets had the row of boxes to write out the AC various die rolls would hit, but that's not using THAC0; it's just copying the table from the DMG.

I do think the BAB was one of the best changes in 3e and was glad to see them keep it in 4e. I don't love it enough that I'd ever try to reverse engineer older editions, but I sure wouldn't use THAC0.

So, my opinion:

BAB >> to-hit tables >> THAC0

 

[Obryn]

All math is just addition.

Addition = ....addition
Subtraction = adding the negative
Multiplication = adding something to its self a number of times
Division = adding a part rather than a whole of something to something else.

Is this really your argument?

"Subtraction is just as easy as addition, since subtraction is just adding a negative number."

"Multiplication is just as easy as addition, since it's just adding numbers a lot of times."

I think that's a rather specious argument that doesn't consider how an actual human brain deals with numbers.

-O

 

[justanobody]

THAC0's explanation always seemed a little weird to me.

The lower your AC/THAC0, the better. You want to roll high, but your final attack value must be lower than your opponent's AC for you to hit.

Dave created the system based on naval vessel rqtings, where the lower number was better.

Think of it like spaceships vs watercraft, and underwater craft.

We live at 1 atmosphere. Spaceships must be built to survive 0 atmospheres.

Normal ships require 1 atmosphere to not be crushed under Earth's gravity.

So a spaceship can survive 1 and 0 atmospheres.
Watercraft can survive at least 1 atmosphere.
Underwater craft can survive 1 atmosphere, 2 atmospheres, etc as they can go deeper.

The ratings i think go negative to show how far below sea level a vessel can travel before it reaches crush depth.

so a -1 rating would mean it can withstand twice normal atmospheric conditions or 32.x PSI from the outside.

Which is what a hit is in regards to damaging something. Pressure from the outside needed to cause damage.

So something with a -2 rating could take more pressure before being damaged than something with a 1 or -1. Thus THAC0 and its use of lower equals better.

Its what happens when smart people make games with technical backgrounds.

You could always rewrite THAC0 and have the numbers go up. that is all BAB did. same sytem, just different window dressing.

But i hope that explains a bit why the lower numbers were better with THAC0. maybe on of the Dragon Magazines gives it in better detail. Check that thread to see if it has been mentioned yet by un in "reading the entire run".

So all in all the main problem with the THAC0 system, is people just get caught up on the math. All there is to it.

So for anyone having problems with THAC0, just use the one for the players that simple algebra lets you extract that i gave above, and will repeat here:

Player uses:
THAC0 - (Number rolled + modifiers) = AC you can hit

And let the DM do the comparisons.

player number =< AC of target means a successful hit.

 

[Reynard]

Do you think it's that uncommon for people to be able to experience the rules of the game and the fictional world of the game at the same time, without one interfering with the other? The ability to do that sounds like a requirement for enjoying role-playing games.

Many years, many people and many game systems tells me that few, if any, people do each in equal measure, and that the system in question has the largest effect on which aspect is prevalent at any given moment (though individuals' experience level with a particular system will also have an impact). Basically, when calculations or rules/sheet referencing is required during play, immersion suffers. Note that this has nothing to do with role-playing -- immersion is a completely separate issue and one i think has a far greater impact on the final "fun" quotient.

In short: yes, I think it is uncommon for people experience the rules of the game and the immersive aspect of play in equal measure.

 

[Filcher]

Dave created the system based on naval vessel rqtings, where the lower number was better. [snip]

This was an awesome history lesson.

 

[justanobody]

Is this really your argument?

"Subtraction is just as easy as addition, since subtraction is just adding a negative number."

"Multiplication is just as easy as addition, since it's just adding numbers a lot of times."

I think that's a rather specious argument that doesn't consider how an actual human brain deals with numbers.

-O

The human brain is a moot point.

Math is math.

2 + 2 will always equal 4 in a base10 system.
2 -(-2) will also always equal 4 in a base10 system.

My arguement was the way people look at THAC0. Again se the Player one presented and you get the same math, but a different variable. It just takes the algebra to manipulate the equation to get what you need.

A - X = B

you have to solve for X so do it before you do the math.

You know you dont have X so solve for X.

A - X + X = B + X
Since X - X = 0 remove them from the left hand side

A - (-B) = B + X - B
Since B - B = 0 remove them from the right hand side

A + B = X

Now you just have to plug in the A and B to find your X that you dont know.

So rather than using a DM view of the formula, since he knows your THAC0 by asking, and knows the AC...

THAC0 - AC = # needed to hit (dice roll + modifiers)

The DM can tell you what you need to roll with your modifiers to hit.

Use the player view of what you know. Your modifiers, your THAC0, and what the dice gives you and tell the DM what AC you can hit.

THAC0 - (Number rolled + modifiers) = AC you can hit

Same equation, different looks at it depending on your knowns and the variables you have available to YOU.

Just depends on what you are trying to figure out.

You don't need a monsters AC to know what you can hit. You don't ever need to know it, but can figure it out. That was my point.

Since a list of monsters ACs are not provided in the PHB, you use what you know to determine what you can do. Heaven forbid someone creating something on their own and someone doesn't know its AC by looking it up in a published book!

So like the rest of the game, take the information you have, and determine what to do with it. Don't trivialize over a chance to hit, just because of the math.

You have two doors to pick from. how do you know which one is the right door when you enter a room form a third door. You use what you know, or look for the right clues. You know the correct door isn't the one you entered from.

THAC0 gave you all the clues you needed represented in mathematical expressions.

So use the information given to figure out what you need to do. Be it with THAC0, BAB, or picking between those two unopened doors.

 

[Obryn]

The human brain is a moot point.

Math is math.

When it's human brains - not computers - actually doing the calculations in real-time at the game table, it's anything but a moot point.

As for the rest - I don't really know how it applies. I know THAC0, and I know BAB. I don't need a discussion of base 10 calculations. As a real person and a DM, I'm concerned about two things:

(1) Numbers that are easy to grasp for real people, including casual gamers.
(2) Quick calculations at the table.

I think BAB and positive ACs fit criterion 1 perfectly. "High is good" is the natural way peoples' minds work, and it fits in with their expectations.

Also, addition is quicker and more intuitive than subtraction for the human brain, so criterion 2 is fulfilled.

-O

 

[Umbran]

The human brain is a moot point.

Math is math.

Oh, really?

There's a song by Tom Lehrer called "New Math". It goes through the process of subtracting 173 from 342, in base ten and then base 8.

Folks who went through school from the 1960s and onward don't get what's so funny. He's just doing arithmetic as we learned it. The funny thing is that the folks who learned arithmetic earlier did it differently, such that during the transition (when the song was written), parents had difficulty helping their kids do their homework - the parents could get the same answer (because math is math), but confused their kids when they tried to show them how to get that answer, because the schoolteacher showed them something else.

You can, if you wish, go about the process of adding 19 and 1 via set theory, starting at the definition of the null set and working your way up. But you'd not want to do that at the gaming table. Rather cumbersome. THAC0 is notably less cumbersome than set theory, but a bit more cumbersome than BAB.

 

[justanobody]

Right. Bigger is better. How is your bag phone working for you now? How about that phonograph you carry your music around on to listen to? Not to forget that 14 inch quill you use and ink pot to dip it in and the scrolls on which you write.

I have no idea what you do when you have a minotaur that just cant fit through a hole in a wall. Probably make the hole bigger rather than let the gnome or other creature go through it and unlock the door for everyone else.

 

[Obryn]

Right. Bigger is better. How is your bag phone working for you now? How about that phonograph you carry your music around on to listen to? Not to forget that 14 inch quill you use and ink pot to dip it in and the scrolls on which you write.

I have no idea what you do when you have a minotaur that just cant fit through a hole in a wall. Probably make the hole bigger rather than let the gnome or other creature go through it and unlock the door for everyone else.

I really don't know how this applies, unless you honestly don't understand human psychology and the way the human mind interprets numbers.

I know you want to make this an issue of pure math, but pure math gets distorted once you add people. Human brains are not perfect computers; they exhibit tendencies and preferences. If you ignore those tendencies and preferences, you end up with confusion.

-O