[MUD-Dev] Understanding Simulation (was: Point of View)

[Ted L. Chen]

John Robert Arras Wrote
> On Sun, 22 Sep 2002 listsub at wickedgrey.com wrote:

> But it should be. You can do so much more then. Instead of
> attacking when players are there, set up populations and have them
> attack whenever they feel like it. Maybe players are there, maybe
> they aren't. Maybe they do something, maybe they don't. If they
> aren't there, then they could find out through news or rumors of
> some kind that propogate throughout the world. If you set up
> general "population" code, then you have to do it once, and never
> have to think about it again. And, if you improve the code, then
> you get improvements across the board.

[ lots of snippage ]

Not to harp on John - as he's not the only self-proscribed
simulationist on this list - but I roll my eyes whenever someone
offers the roaming wolf example as if that system would be stable
throughout the course of any game.  Raph and some of the boys from
UO in the early days can probably attest to the stability of
programmed ecology systems.

So in hopes of helping people break out of the "Star Trek Simulation
Syndrome", I suggest that anyone seriously interested in simulation
as a tool for MMOGs to read up on:

  "Road Maps: A Guide to Learning System Dynamics"
  from the MIT System Dynamics in Education Project
  http://sysdyn.mit.edu/road-maps/rm-toc.html

It's a useful primer if academic text-books strike fear in your
hearts.  It's in small PDF chunks that start from the very beginning
and works its way up in complexity.  The examples are based on their
learning program STELLA but I think most readers here are
comfortable enough with computers to make due without it.

Road Maps #1 through #5 will show you the basic structures.

Things get more interesting and applicable to MMOGs at Road Map #6,
where they start to combine the elements learned in "Economics
Supply and Demand" Something of interest for anyone interested in
player-driven economies.  Most people assume equilibrium from the
get go, and the example serves to illustrate the oscillation that
occurs in even a simple system that uses the most basic of rules.
For those pondering a purely player-driven economy, I suggest you
take and play with the model.  I've been playing with the effects of
demand noise and have destablized the system with only 15% noise.
If you want the matlab code or discuss the specifics in detail,
email me off list.

For those who wish for close-system ecologies, I suggest looking at:
"Generic Structures: S-shaped growth I" in Roadmap #5.  "Oscillating
Systems 2: Sustained Oscillation" in Roadmap #8.  then "Generic
Structures: Overshoot and Collapse" in Roadmap #9.

   Overshoot and collapse is a behavior in which a stock, in the
   case of Goldfield, the population of the town, relies upon a
   depletable resource, gold. When the gold is abundant, the
   population grows quickly. As the population grows, however, it
   depletes the supply of gold. When gold becomes scarce, the
   population drops rapidly as the miners leave to try their luck
   elsewhere.

The first two are what I think most people expect with ecology
models.  Birth, food, death.  But those systems are only valid if
there are no external factors (or if those factors are constant).
So unless you keep your wolf population numbers independent of
everything else (including players) you're going to have an
interesting time keeping it active.

If you're still reading up to now and have thought that negative
feedback loops can solve everything, I can also point you toward
excellent textbooks on nonlinear control systems to disway you from
that theory.

So, are complex systems based on simple rules possible?  Of course
they are.  Nature is a prime example of that.  But don't discount
all the natural extinctions that have occurred in the past.  So
unless you're cool with resetting your players every few days,
losing all content you've created so far (wolf meat is no longer
available... they're extinct!), all in the attempt to find that rare
local equilibrium point, I really suggest reading up and
understanding what simulation can and cannot do.

So bringing it all back, John was making the point of coding the
rules of the dynamic systems, letting it run (based on those rules),
and generate the story from that.  To which I have to say is
fiddlesticks.  If you want an interesting story from such a system,
you're going to need a lot of factors and dependencies in that
simulation.  And by "a lot", I mean any number greater than 3.
Which unfortunately, is already one too many.


TLC


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