# [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
oddities.

> 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
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
than others.

--
J C Lawrence                               Internet: claw at null.net
(Contractor)                               Internet: coder at ibm.net
---------(*)                     Internet: claw at under.engr.sgi.com
...Honourary Member of Clan McFud -- Teamer's Avenging Monolith...

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