<s>
ARToolKit	O
is	O
an	O
open-source	O
computer	O
tracking	O
library	O
for	O
creation	O
of	O
strong	O
augmented	B-General_Concept
reality	I-General_Concept
applications	O
that	O
overlay	O
virtual	O
imagery	O
on	O
the	O
real	O
world	O
.	O
</s>
<s>
Currently	O
,	O
it	O
is	O
maintained	O
as	O
an	O
open-source	O
project	O
hosted	O
on	O
GitHub	B-Application
.	O
</s>
<s>
In	O
order	O
to	O
create	O
strong	O
augmented	B-General_Concept
reality	I-General_Concept
,	O
it	O
uses	O
video	O
tracking	O
capabilities	O
that	O
calculate	O
the	O
real	O
camera	O
position	O
and	O
orientation	O
relative	O
to	O
square	O
physical	O
markers	O
or	O
natural	O
feature	O
markers	O
in	O
real	O
time	O
.	O
</s>
<s>
So	O
ARToolKit	O
solves	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>
ARToolKit	O
was	O
one	O
of	O
the	O
first	O
AR	O
SDKs	O
for	O
mobile	O
,	O
seen	O
running	O
first	O
on	O
Symbian	B-Operating_System
in	O
2005	O
,	O
then	O
iOS	B-Application
with	O
the	O
iPhone	O
3G	O
in	O
2008	O
,	O
and	O
finally	O
Android	B-Application
as	O
early	O
as	O
2010	O
with	O
a	O
professional	O
version	O
by	O
ARToolWorks	O
later	O
in	O
2011	O
.	O
</s>
<s>
ARToolKit	O
was	O
acquired	O
by	O
DAQRI	B-Device
and	O
re-released	O
open-source	O
starting	O
at	O
version	O
5.2	O
on	O
May	O
13	O
,	O
2015	O
,	O
including	O
all	O
of	O
the	O
features	O
that	O
were	O
previously	O
only	O
available	O
in	O
the	O
professional	O
licensed	O
version	O
.	O
</s>
<s>
Tracking	O
of	O
simple	O
black	O
squares	O
(	O
any	O
square	O
marker	B-Architecture
patterns	I-Architecture
)	O
.	O
</s>
<s>
Plugins	B-Application
for	O
Unity	B-Application
and	O
OpenSceneGraph	O
.	O
</s>
<s>
Optical	B-General_Concept
head-mounted	I-General_Concept
display	I-General_Concept
support	O
.	O
</s>
<s>
Free	B-Application
and	I-Application
open	I-Application
source	I-Application
software	I-Application
.	O
</s>
<s>
The	O
current	O
version	O
of	O
ARToolKit	O
supports	O
Microsoft	B-Application
Windows	I-Application
,	O
Mac	B-Operating_System
OS	I-Operating_System
X	I-Operating_System
,	O
Linux	B-Application
,	O
iOS	B-Application
,	O
and	O
Android	B-Application
platforms	I-Application
.	O
</s>
<s>
Other	O
versions	O
of	O
ARToolKit	O
have	O
also	O
been	O
ported	O
to	O
Symbian	B-Operating_System
,	O
and	O
Windows	B-Application
Phone	O
to	O
support	O
mobile	O
AR	O
applications	O
.	O
</s>
<s>
ARToolKit	O
is	O
also	O
available	O
as	O
a	O
plugin	B-Application
for	O
the	O
Unity	B-Application
game	I-Application
engine	I-Application
for	O
example	O
to	O
align	O
a	O
virtual	O
camera	O
within	O
Unity	B-Application
with	O
a	O
real-world	O
camera	O
relative	O
to	O
a	O
tracked	O
marker	O
target	O
and	O
taking	O
care	O
of	O
communicating	O
with	O
the	O
camera	O
.	O
</s>
<s>
The	O
plugin	B-Application
supports	O
Unity	B-Application
on	O
OS	B-Operating_System
X	I-Operating_System
,	O
Unity	B-Application
on	O
Windows	B-Application
,	O
Unity	B-Application
on	O
Android	B-Application
,	O
and	O
Unity	B-Application
on	O
iOS	B-Application
.	O
</s>
