Game Development Reference
In-Depth Information
•
ARToolKit markers
: These are very popular. They look like thick, square
frames with simple contrast symbols inside. The system is notable for its use
of Japanese Kanji characters as standard patterns (pretty cyberpunk nov-
el, isn't it?), since ARToolKit was originally created by Dr. Hirokazu Kat from
Japan. One common marker displays the Kanji symbol: which looks like a
letter "A" without a crossbar and means human
.
Of course, other types of
images can be used, including the Latin alphabet, graphic illustrations, and
so on. This is an advantage because it can make the design very human
friendly.
•
ARTag
: This is a more advanced alternative to the traditional ARToolKit
markers, with fewer errors and good overall performance. Our system looks
like a grid of matrix barcodes in a small dimension (6 x 6 cells); they cover
the screen surface like some sort of digital pattern. Because there are a lot
of tiny markers, the accuracy of recognizing something that is displayed on
the screen is pretty high. If some of the markers are unreadable to a camera
because of the environment conditions or some occlusions, the other ones
may ensure the process takes place. In some sense, ARTag markers can be
considered a cheap alternative to advanced systems that scan surroundings
in depth. If an object in the surrounding environment is extensively covered
with markers, AR applications will perceive and include them in the impro-
vised virtual mapping. The disadvantage of ARTags is their machine-friendly
look, as the design is too technical.
•
Siemens Corporate Research (SCR) markers
: This system has an attract-
ive simplification as any marker looks like a square array of big dots (4 x 4
elements) and it is very easy to produce, even by drawing them by hand us-
ing a marker pen. Besides being logical code, SCR markers look good as
dots look pretty harmonic. A similar approach to designing markers is used
by the talented indie game developer, int13 (
http://int13.net
)
, in their AR pro-
jects, and they have proved the efficiency of the markers.
•
Canon markers
: These are graphic reference points developed by Canon
for its head-mounted display called MREAL. The markers consist of a black
frame and hexagonal grid of elements inside the display screen. The design
looks pretty elegant and according to developers, has few errors.
•
reacTIVision markers
: One of the most original reference symbol designs is
used in an open-source computer vision framework called reacTIVision (
ht-