[MUD-Dev] Re: Systems you use
J C Lawrence
claw at under.engr.sgi.com
Thu Apr 23 10:39:49 New Zealand Standard Time 1998
On Thu, 23 Apr 1998 13:17:52 +0100 (BST)
Ling <K.L.Lo-94 at student.lboro.ac.uk> wrote:
> Out of interest, what system do people use for their randomness and
> why? Here's a list of some of the ones I can immediately remember
> with short explanations of how I know they're used.
I have a random number generator which claims to be "non-lumpy"
(picked it out of DDJ some years ago).
> Linear probability, percentile, 1D100, 1D20: Self-explanatory,
> probably the most popular one. Often conducted as a 'roll higher to
> succeed'. Eg: 60% chance of hitting someone, minus their defensive
> modifiers, plus attacking modifiers. Roll over to achieve.
> Variants include systems using a float those value hovers between 0
> and 1 (simply a finer version) and Palladium games using a 1D20.
I use percentile variants almost exclusively. Choice of suitable
multiple break points for your criteria can make almost any curve form
-- including the multiple-roll/extreme-peak/trough variations. Note:
I've found it easier and sufficiently cheap to use the multiple-roll
technique for the very low probability oddities to not bother with
figuring the appropriate percentile marks to get the same curve.
> Strange multiple D6 only: Easier to give examples for this one.
> For Heavy Gear (DP9): character rolls number of D6's equal to their
> skill. Complete 1's result in a fumble. Result of the roll is
> equal to the highest die rolled. In the event of multiple 6's,
> additional 6's contribute a +1 to the roll. Coz of this, the
> probability curve is *highly* non-linear after 7. Simple, quick.
Note: I use a *lot* of non-linear curves. My random function returns
a 64bit unsigned integer. I then define value ranges for the vcarious
responses, at leat one of which ranges results in a further (possibly
several) number generation(s) for torqued curves. I could of cour do
the same thing by defining very small sub-ranges for the torques, but
accuracy of probability definition suffers as well as ease of defining
> Combat Resolution Table (CRT): Advocated by Steve Jackson (of SJG
> fame). Attacking strength and defensive strength are turned into a
> ratio and a single die is rolled to get a list of potential results.
> Eg: Hovercraft Alpha with fires with a strength of 3 at APC Beta
> with defence of 2, ratio is 3:2. A table might look something like:
I do cascaded effects. I guess in a way I use a generated table (its
really just an f(x) return), to determine the result of a given
attempted action. I then use that result to determine what resultant
actions to compute.
> Other: Random numbers are dependent upon stats. Eg: Strength of 200
> will allow rolls of 1-200 or variation of.
Yup, I use stats (well, probability fields -- see earlier discussion)
to modify and warp the base curves and distributions.
> When it comes down to it, some of the systems listed can emulate the
> others so it is all down to a matter of preference.
This is the real point. When you get right down to it any probability
system can be described in terms of any other probability system. The
only *real* advantage (other than comutational load) of any system
over another is the mental model it gives the programmer/user. People
find some models easier to "think with" and to apply to new situations
J C Lawrence Internet: claw at null.net
(Contractor) Internet: coder at ibm.net
---------(*) Internet: claw at under.engr.sgi.com
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