cially available affordable
wearable computers and
head-mounted displays
(HMDs), it is possible to
cations suitable for an outdoor environment.
We extended an existing desktop game and
developed it into the ARQuake system [4], one
of the first systems that allows users to play aug-
mented reality games outdoors--allowing them
to move in the physical world, and at the same
time experience computer-generated graphical
monsters and objects.
person-perspective, shoot-em-up game ini-
tially released in 1996. In Quake, the player
runs around a virtual world, shooting at mon-
sters, collecting objects, and completing objec-
tives. The game is desktop-based, with the
board, and mouse. Although the game is rela-
tively old, the graphics engine is very powerful
and runs on a wide range of computing hard-
ware. Recently, id Software released the source
code for Quake, making it possible for enthu-
siasts and researchers to modify the game for
their own purposes.
images over a user's view of the physical world.
Using a transparent HMD placed on the user's
head, an internal half-silvered mirror com-
bines images from an LCD display with the
user's vision of the world (see Figure 1). By
combining this display technology with a
wearable computer, it is possible for the user
to walk outdoors and visualize graphical
objects that are not normally visible. A com-
prehensive survey article [1] discusses most
aspects of this research area.