<s>
An	O
ARTag	B-Application
is	O
a	O
fiducial	B-Architecture
marker	I-Architecture
system	O
to	O
support	O
3D	O
registration	O
(	O
alignment	O
)	O
and	O
pose	B-Operating_System
tracking	I-Operating_System
in	O
augmented	B-General_Concept
reality	I-General_Concept
.	O
</s>
<s>
Like	O
the	O
earlier	O
ARToolKit	B-General_Concept
system	O
,	O
they	O
allow	O
for	O
video	O
tracking	O
capabilities	O
that	O
calculate	O
a	O
camera	O
's	O
position	O
and	O
orientation	O
relative	O
to	O
physical	O
markers	O
in	O
real	O
time	O
.	O
</s>
<s>
Once	O
the	O
camera	O
's	O
position	O
is	O
known	O
,	O
a	O
virtual	O
camera	O
can	O
be	O
positioned	O
at	O
the	O
same	O
point	O
,	O
revealing	O
the	O
virtual	O
object	O
at	O
the	O
location	O
of	O
the	O
ARTag	B-Application
.	O
</s>
<s>
It	O
thus	O
addresses	O
two	O
of	O
the	O
key	O
problems	O
in	O
Augmented	B-General_Concept
Reality	I-General_Concept
:	O
viewpoint	O
tracking	O
and	O
virtual	O
object	O
interaction	O
.	O
</s>
<s>
An	O
ARTag	B-Application
appears	O
on	O
the	O
Mars	O
Science	O
Laboratory	O
.	O
</s>
<s>
ARTag	B-Application
is	O
supported	O
by	O
the	O
open	B-Application
source	I-Application
Goblin	O
XNA	O
software	O
.	O
</s>
