[MUD-Dev] Systems you use

[Ling]

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.


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.


Combinational dice, nDm + c (eg: 3D6 + 1):
The usual run of the mill in paper rpgs.  Far too many variants and
systems to list.  Includes AD&D...  :)  Generally looks like a
bell/normal/gaussian/binomial distribution curve with the lumpiness
dependent upon the number of dice used and the range depending upon
size of each die.


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.

For Shadowrun (FASA): character rolls number of D6's equal to their skill.
Any 1's result in a fumble, any 6's allow another roll which is added to
that die roll (so rolling the same die and getting two 6's and a 2 will
give a total of 14).  I'll take a bastardized combat example.  A firearms
weapon could inflict 4L2 damage.  A character with firearms skill of 5
(quite high) needs to roll at least one 4 to hit and inflict Light damage,
for every 2 successes, the damage is increased by one notch.  Pretend the
roll was 4, 2, 4, 5, 6+3.  There are 4 successes in that roll so the damage
is increased twice, from Light to Medium to Heavy (which does 3, 6, 9 damage
respectively, all characters and objects have 10 hitpoints).  Regarding
fumbles, I had a houserule that stated any fumbles are countered by a success.
Btw, there's also 


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:

Ratio		die roll		- miss
	1   2   3   4   5   6		d disabled
2:1     -   -   -   -   -   -		x killed
2:3     -   -   -   -   -   d
1:1     -   -   -   -   d   d
3:2	-   -   -   d   d   x
2:1     -   -   d   d   x   x
3:1     -   d   d   x   x   x 		...etc...


Cards and chits:
Includes Magic: The Gathering (WotC), Awful Green Things from Outer
Space (SGJ), Sword of the Stars (can't remember who?).  Shalln't go into
too much detail into M:TG.  For AGTfOS, weapons/items had unknown effect
on the Awful Green Things until at time of use, a random chit is drawn
to find out - this chit stays with the weapon for the duration of the game.
('Aaargh! Rocket fuel makes them multiply', 'Well you won't do that again!')
In Sword of the Stars, players obtained a number of 'action cards' and
declared their action, assigning each card to the particular action.  Upon
executing the action, the appropriate card was flipped to find out the result.
Characterised by each card containing packets of data instead of being
separate.  (ie: A card might say: Failed action AND this or that side 
effect.)


Other:
Random numbers are dependent upon stats.  Eg: Strength of 200 will allow
rolls of 1-200 or variation of.

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.


  |    Ling Lo of Remora (Top Banana)
_O_O_  Elec Eng Dept, Loughborough University, UK.     kllo at iee.org


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