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Billing Server

Billing
Database

Load Balancer

Chat Server

Game
Database

Game Node 1 .. n

NPC Node 1 .. k

Dispatcher

Firewall

PS2

XBox

GameCube

Apple

Mobile

Web Server

Figure 1: Parallel Cluster Architecture for an actual MMOG

2.3

Virtual World Model

Zereal's MMOG world representation is a roguelike model, mostly inspired by Nethack
(roguelike refers to the game Rogue). Roguelike means that it has simple graphics, typically
a 2D environment with a bird's-eye view of the game. Roguelike also usually means that the
the game has an enormous variety and amount of features [13], but in our simulation platform
we've chosen to provide only some basic features.

The virtual world map is represented as 2D rectangel with borderwalls and doors on the

outer limit of the map, and internal walls with doors inside the map to split it up in rooms
or smaller outside spaces. Researchers at the Intelligent Computer Entertainment Laboratory
at the Ritsumeikan University in Japan has developed a GUI client to Zereal called Zere-
alViewer, see figure 2 for a screenshot.

Figure 2: Parts of a typical Zereal Virtual World

Each map is a subworld which resides on its own processor in the cluster and the sub-

worlds borders each other after a squared model and send players between them. This world
representation is easy to represent in memory, and extension of the world is only limited by
memory and power on the clusternodes. Most landscapes can be "made believe" in the maps,
and the usually resource demanding task of sensing has less complex data to process. Players

Scalable MMOG Player Simulation

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