From: news@sifon.cc.mcgill.ca
Newsgroups: rec.games.frp.advocacy
Subject: Re: Vampire vs. Hero vs. Gurps etc...(Long!)
Date: 23 Nov 92 16:34:34 GMT
Organization: McGill University

In article <1992Nov23.043345.16198@news.columbia.edu> jhk6@cunixb.cc.columbia.edu (John H Kim) writes:

> So what exactly is the flexibility that you are saying is gained
>by having these two rolls? In AD&D you can distinguish an attack which missed
>due to the defender's armor class, and an attack which would have missed
>even if the defender was AC10 (fairly simple, just did he roll less than his
>THAC0 minus 10?).
> I am in no way advocating AD&D here - it's combat system is simplistic
>and ridiculous. I am just saying that a single roll can take just as much into
>account as two rolls. Sometimes it will be easier to represent certain
>probabilities in two rolls rather than one, certainly, and some other
>probabilities are easier to take into account in one roll. But the former
>is not 'innately' more flexible.

Well, John, I'll agree that two rolls are not any more *flexible*;
but there are a few situations where two rolls have some type of
advantage over one. The first is in the case of what most systems
call a "critical success" result. It is generally true that in
this instance, if you have only one roll, the special result is
completely determined right then and there, while if there are
two rolls, the recipient of a critical result has the chance to
counter it with an equally good result.
     In fact, this example is simply a very specific case of
the more general situation where a bell curve is artificially
truncated, or a linear distribution is made non-linear. Using
my system (GURPS) as an example, we always say that a 3 or 4
is success and 17 or 18 is failure, no matter what; as well, we
limit a success number for a resisted ability by an upper bound
of 16. Both of these are truncating operations, and, since they
are not always applied symmetrically, the resulting probability
determination is *not* equal to a single roll on the bell curve.
     The contest situation is not easily represented with a
single roll. What a contest is, in effect, is a situation where
character A is trying to make a roll at minus the amount character
B did. There is a random roll *and* a random modifier, in effect.
This is what a contest can be reduced to. How would one do this
with a single roll? You can't, without being unfair.
     The other **major** reason for a two roll system is that
it allows *both* parties to feel like they are doing something,
which is important in a game. Which is more interesting: the GM
rolling dice and saying "You're hit!", or him rolling dice and
saying "Roll a defense, or you're hit"? What about situations
where two players are competing? Is it fair to let just one
player determine the outcome? I, for one, don't think so!

     In a sense, we're mixing apples and oranges here. There
are a few distinct philosophies out there: the Hero-like

ROLL = FIXED BASE NUMBER + ATTACKER'S MOD - DEFENDER'S MOD

the AD&D-like

ROLL = MATRIXED ATTACKER'S ABILITY vs. DEFENDER'S PROTECTION
       +/- SITUATION MODIFIERS FOR ATTACKER and/or DEFENDER

system; and the GURPS-like

MAX( ATTACKER'S MARGIN OF SUCCESS , DEFENDER'S MARGIN OF SUCCESS )

philosophy.
     There is a lot to recommend all of the above, but comparing
them as techniques, in the absence of the underlying rules system,
is a fruitless and hopeless debate.

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