[MUD-Dev] Geographical space paritioning

[ceo]

Adam Martin (that's me) wrote::

> ...You want to be abstracting things that work together in
> practical terms e.g. by looking at working-sets (c.f. a google
> search for "working set" if you don't know the term) and making
> sure each clump of related/non-independent data is grouped
> together in the abstraction. ISTR JC spoke a couple of times about
> dependent working sets on the night before the MDC (in relation to
> a dicussion on geographical partitioning).

Which reminds me that I think I never finished explaining why
geographical partitioning just doesn't work in general, unless you
have close to trivially small groups of players. If those of you who
were in that conversation can bear for me to have another go at
it... ;). (although finishing this post I just got a severe case of
deja vu, so apologies if I *have* already explained this).

The gist is that your working-sets don't coalesce into nice small
independent clumps, unless you play god with your game design and
pretty much force them to (having a game played entirely underground
in a huge maze would be a nice simple way of achieving this).

They tend more often to coalesce into huge clumps in small areas
(too big for a single server to handle) or into lots of small clumps
that keep touching each other and producing chains of
inter-dependent working-sets. This ends up producing transitory
working-sets that are huge, but keep splitting and recombining at a
high rate.

If you design your game around this, no problem. If it's a critical
part of your game design that the world is open (which covers a lot
of the current RPG-style MMOG's at the moment), then geographic
partioning is a dead-end. Mountains are obviously one of your best
friends, especially if you don't allow anyone to walk along the
ridgetops (make it too steep in the last 10 feet below the summit).

Particular problems for games that allow a lot of flying, especially
at low speed on a normal-sized landscape. Even worse if the game has
a large number of players walking around on the ground, which could
cause everyone in the air to be linked to everyone else almost
everywhere. Ouch.

P.S. Dan, do you remember which book it was:

  "There is an article about these movable cell boundaries in one of
  the multiplayer game development books. It has some anecdotes
  about how traumatic a scheme like this can be, and it was more
  than enough to put me off."

Adam M
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