Distributed Mobile Multi-User Urban Simulation
Alan Cummins Carol O’Sullivan∗
This sketch gives an overview of the completed and ongoing
research involved in developing a 3D multi-user environment on
low-end mobile devices.
The overall aim of our research is to produce a distributed multi-
user virtual model of Dublin City (Figure 1) on low-end mobile
devices such as Personal Digital Assistants (PDA, Figure 2). The
project uses the model developed for the Virtual Dublin Project
[Hamill and O’Sullivan 2003]. There are two main areas to be
• Rendering: The display of 3D models of the buildings is an
area, which is very much influenced by the limited amount of
memory and storage space available on the PDAs.
• Distribution: This includes the multi-user factor, which
allows users that are logged onto the system to communicate
with each other.
To date three main areas of research have been focused upon to
speed up rendering times:
• Visibility Culling: Removal of parts of a given scene if they
are obscured by other buildings or are out of view.
Level of detail Rendering: Rendering of a given model at
various levels of detail allowing for a scene to be tailored for
the desired frame rate.
Impostor-based techniques: The use of flat 2D images to
build up a false impression of 3D scene information.
Figure 1. Screen Shots of TCD buildings
Also influencing rendering times of buildings and the correct
display of mobile clients locations is the factor that networked
mobile units constantly change point of access [Karimi et al.
2001]. This can result in packages requiring multiple hops via
mobile clients’ in the network from the point of leaving the server
to being received by the required mobile client instead of the
package being sent directly by the server to the client in one hop.
These multiple hop packages require more time to be received and
processed so that buildings are displayed in