<s>
FreeTrack	B-Operating_System
is	O
a	O
general-purpose	O
optical	B-Application
motion	I-Application
tracking	I-Application
application	O
for	O
Microsoft	B-Application
Windows	I-Application
,	O
released	O
under	O
the	O
GNU	B-License
General	I-License
Public	I-License
License	I-License
,	O
that	O
can	O
be	O
used	O
with	O
common	O
inexpensive	O
cameras	O
.	O
</s>
<s>
Its	O
primary	O
focus	O
is	O
head	B-Application
tracking	I-Application
with	O
uses	O
in	O
virtual	B-Application
reality	I-Application
,	O
simulation	O
,	O
video	O
games	O
,	O
3D	O
modeling	O
,	O
computer	B-Application
aided	I-Application
design	I-Application
and	O
general	O
hands-free	O
computing	O
to	O
improve	O
computer	O
accessibility	O
.	O
</s>
<s>
Windows-compatible	O
video	O
devices	O
like	O
webcams	B-Protocol
are	O
supported	O
,	O
as	O
well	O
as	O
special	O
Nintendo	B-Device
Wii	I-Device
Remote	I-Device
camera	O
,	O
iPhone	O
Truedepth	O
camera	O
with	O
Eyeware	O
Beam	O
,	O
and	O
NaturalPoint	O
cameras	O
(	O
TrackIR	B-Operating_System
,	O
SmartNav	O
and	O
OptiTrack	O
)	O
.	O
</s>
<s>
FreeTrack	B-Operating_System
can	O
output	O
head-tracking	O
data	O
to	O
programs	O
directly	O
using	O
its	O
own	O
open	O
interface	O
,	O
as	O
well	O
as	O
TrackIR	B-Operating_System
,	O
SimConnect	O
and	O
FSUIPC	O
interfaces	O
.	O
</s>
<s>
Programs	O
that	O
support	O
these	O
interfaces	O
are	O
regarded	O
as	O
being	O
FreeTrack-compatible	O
.	O
</s>
<s>
FreeTrack	B-Operating_System
can	O
also	O
emulate	O
mouse	B-Device
,	O
keyboard	B-Device
,	O
and	O
joystick	B-Device
(	O
via	O
PPJoy	O
)	O
if	O
a	O
program	O
does	O
not	O
support	O
a	O
direct	O
interface	O
.	O
</s>
<s>
FreeTrack	B-Operating_System
is	O
coded	O
in	O
Delphi	B-Language
7	I-Language
and	O
uses	O
DirectShow	B-Library
and	O
DirectX	B-Application
.	O
</s>
<s>
Head	B-Application
tracking	I-Application
is	O
achieved	O
using	O
implementations	O
of	O
DeMenthon	O
's	O
four-point	O
iterative	O
pose	B-Architecture
estimation	O
algorithm	O
(	O
POSIT	O
)	O
and	O
Alter	O
's	O
three	O
point	O
geometric	O
algorithm	O
.	O
</s>
<s>
FreeTrack	B-Operating_System
uses	O
a	O
camera	O
to	O
collect	O
real-time	O
information	O
on	O
the	O
point	O
model	O
worn	O
by	O
the	O
user	O
.	O
</s>
<s>
These	O
coordinates	O
are	O
used	O
to	O
generate	O
an	O
estimate	O
of	O
the	O
real	O
head	O
pose	B-Architecture
,	O
which	O
can	O
be	O
transformed	O
by	O
the	O
user	O
in	O
a	O
number	O
of	O
ways	O
to	O
create	O
a	O
virtual	O
pose	B-Architecture
.	O
</s>
<s>
Finally	O
,	O
the	O
virtual	O
pose	B-Architecture
is	O
sent	O
to	O
the	O
user	O
's	O
choice	O
of	O
outputs	O
.	O
</s>
<s>
A	O
3D	O
preview	O
is	O
available	O
that	O
shows	O
the	O
virtual	O
head	O
position	O
and	O
orientation	O
for	O
a	O
given	O
real	O
head	O
pose	B-Architecture
and	O
can	O
be	O
viewed	O
from	O
multiple	O
perspectives	O
,	O
including	O
first-person	O
.	O
</s>
<s>
Keyboard	B-Device
,	O
mouse	B-Device
and	O
joystick	B-Device
buttons	O
can	O
be	O
used	O
to	O
toggle	O
tracking	O
settings	O
,	O
including	O
the	O
virtual	O
centre	O
location	O
(	O
like	O
adjusting	O
the	O
seat	O
position	O
in	O
a	O
car	O
)	O
and	O
individually	O
toggle	O
axes	O
and	O
outputs	O
.	O
</s>
<s>
For	O
NaturalPoint	O
cameras	O
,	O
FreeTrack	B-Operating_System
can	O
provide	O
advanced	O
features	O
and	O
a	O
level	O
of	O
customization	O
that	O
is	O
not	O
available	O
with	O
official	O
software	O
.	O
</s>
<s>
+	O
Comparison	O
of	O
some	O
cameras	O
compatible	O
with	O
FreeTrack	B-Operating_System
Camera	B-Algorithm
Sensor	I-Algorithm
resolution	O
FPS	O
Sensor	B-Algorithm
Angle( °	O
)	O
Output	O
CPU	B-Device
usage	I-Device
Subpixel	O
precision	O
IR	O
LEDs	O
Approx	O
.	O
</s>
<s>
price	O
(	O
USD	O
)	O
Ideal	O
webcam	B-Protocol
640×480	O
≥60	O
monochrome	O
42	O
highly	O
compressed	O
small	O
Software-dependent	O
Yes	O
?	O
</s>
<s>
OEM	O
IR	O
webcam	B-Protocol
640×480	O
30	O
color	B-Algorithm
42	O
JPEG	B-Application
compressed	I-Application
small	O
Software-dependent	O
Yes	O
$5	O
Sony	O
PlayStation	B-General_Concept
EyeToy	I-General_Concept
640×480	O
30	O
color	B-Algorithm
56	O
JPEG	B-Application
compressed	I-Application
small	O
Software-dependent	O
No	O
$16	O
Sony	O
PlayStation	B-Device
3	I-Device
Eye	I-Device
640×480	O
187@320x240(CLEye )	O
,	O
125@320x240(Directshow )	O
,	O
75@640x480(DirectShow )	O
color	B-Algorithm
75	O
,	O
56	O
JPEG	B-Application
compressed	I-Application
,	O
raw	O
small	O
Software-dependent	O
No	O
$24	O
Microsoft	O
Xbox	B-Device
Live	I-Device
Vision	I-Device
640×480	O
60	O
@320	O
×240	O
,	O
30	O
@640	O
×480	O
color	B-Algorithm
?	O
</s>
<s>
JPEG	B-Application
compressed	I-Application
,	O
raw	O
small	O
Software-dependent	O
No	O
$14	O
Nintendo	B-Device
Wii	I-Device
Remote	I-Device
128×96	O
100(Bluetooth )	O
,	O
250(I2C )	O
color	B-Algorithm
41	O
point	O
coordinates	O
none	O
1/8	O
No	O
$23	O
NaturalPoint	O
TrackIR	B-Operating_System
1	O
60k	O
pixels	O
(	O
e.g.	O
</s>
<s>
300×200	O
)	O
60	O
monochrome	O
33	O
binary	B-Algorithm
threshold	I-Algorithm
minimal	O
Yes	O
retired	O
NaturalPoint	O
TrackIR	B-Operating_System
2	O
60k	O
pixels	O
(	O
e.g.	O
</s>
<s>
300×200	O
)	O
100	O
monochrome	O
33	O
binary	B-Algorithm
threshold	I-Algorithm
minimal	O
Yes	O
retired	O
NaturalPoint	O
TrackIR	B-Operating_System
3	O
355×288	O
80	O
monochrome	O
33	O
binary	B-Algorithm
threshold	I-Algorithm
minimal	O
Yes	O
retired	O
NaturalPoint	O
TrackIR	B-Operating_System
3	O
Pro	O
355x288	O
120	O
monochrome	O
33	O
binary	B-Algorithm
threshold	I-Algorithm
minimal	O
Yes	O
retired	O
NaturalPoint	O
TrackIR	B-Operating_System
4	O
Pro	O
355×288	O
(	O
subsampled	O
at	O
710×480	O
)	O
120	O
monochrome	O
46	O
binary	B-Algorithm
threshold	I-Algorithm
minimal	O
1/20th	O
Yes	O
$99.95	O
NaturalPoint	O
TrackIR	B-Operating_System
5	I-Operating_System
640×480	O
120	O
monochrome	O
51.7	O
grayscale	O
threshold	O
minimal	O
1/150th	O
Yes	O
$149.95	O
NaturalPoint	O
SmartNav	O
1/2	O
60k	O
pixels	O
(	O
e.g.	O
</s>
<s>
In	O
most	O
cases	O
a	O
resolution	O
of	O
320×240	O
is	O
sufficient	O
,	O
this	O
is	O
capable	O
of	O
producing	O
a	O
much	O
higher	O
sub-pixel	B-Algorithm
resolution	I-Algorithm
,	O
enough	O
to	O
allow	O
accurate	O
cursor	O
control	O
on	O
a	O
high-resolution	B-Algorithm
monitor	O
.	O
</s>
<s>
Resolutions	O
640×480	O
and	O
above	O
have	O
diminishing	O
returns	O
and	O
correspond	O
to	O
an	O
exponential	O
increase	O
in	O
CPU	B-Device
usage	I-Device
when	O
not	O
sufficiently	O
compressed	O
before	O
reaching	O
the	O
computer	O
.	O
</s>
<s>
The	O
Wii	O
utilizes	O
a	O
low-resolution	O
128×96	O
sensor	B-Algorithm
,	O
which	O
is	O
found	O
by	O
some	O
to	O
produce	O
jittery	O
tracking	O
and	O
may	O
require	O
smoothing	O
to	O
improve	O
stability	O
at	O
the	O
cost	O
of	O
decreased	O
responsiveness	O
.	O
</s>
<s>
For	O
the	O
same	O
resolution	O
,	O
monochrome	O
sensors	B-Algorithm
can	O
resolve	O
finer	O
details	O
much	O
better	O
than	O
color	B-Algorithm
sensors	B-Algorithm
due	O
to	O
the	O
lack	O
of	O
a	O
color	B-Algorithm
filter	I-Algorithm
array	I-Algorithm
.	O
</s>
<s>
FreeTrack	B-Operating_System
uses	O
interpolation	B-Algorithm
with	O
low-frame-rate	O
video	O
devices	O
to	O
improve	O
panning	O
smoothness	O
.	O
</s>
<s>
However	O
,	O
responsiveness	O
is	O
fundamentally	O
limited	O
to	O
the	O
frame	O
rate	O
;	O
a	O
30	O
frame/s	O
webcam	B-Protocol
has	O
a	O
maximal	O
response	O
delay	O
of	O
33.3	O
milliseconds	O
compared	O
with	O
8.33	O
milliseconds	O
for	O
a	O
120	O
frame/s	O
camera	O
.	O
</s>
<s>
To	O
put	O
this	O
into	O
perspective	O
,	O
a	O
human	O
’s	O
reaction	O
time	O
to	O
visual	O
stimulus	O
(	O
finger	O
reflex	O
)	O
is	O
typically	O
around	O
200	O
ms	O
;	O
30	O
ms	O
can	O
be	O
regarded	O
as	O
a	O
competitive	O
ping	B-Protocol
in	O
online	O
reflex-based	O
games	O
,	O
and	O
an	O
LCD	O
monitor	O
refresh	O
rate	O
is	O
typically	O
17	O
ms.	O
</s>
<s>
Viewing	O
angle	O
can	O
be	O
reduced	O
by	O
using	O
digital	B-Algorithm
zoom	I-Algorithm
at	O
the	O
cost	O
of	O
resolution	O
.	O
</s>
<s>
The	O
Nintendo	B-Device
Wii	I-Device
Remote	I-Device
effectively	O
uses	O
no	O
CPU	B-Device
,	O
NaturalPoint	O
cameras	O
use	O
a	O
small	O
amount	O
,	O
and	O
general	O
video	O
devices	O
can	O
use	O
a	O
significant	O
amount	O
,	O
depending	O
on	O
the	O
brand	O
and	O
the	O
specific	O
camera	O
settings	O
in	O
use	O
.	O
</s>
<s>
A	O
PlayStation	B-Device
Eye	I-Device
running	O
at	O
the	O
same	O
resolution	O
and	O
frame	O
rate	O
as	O
a	O
TrackIR	B-Operating_System
4	O
would	O
be	O
very	O
demanding	O
on	O
a	O
single-core	O
CPU	B-Device
.	O
</s>
<s>
However	O
,	O
modern	O
multi-core	O
CPUs	B-Device
are	O
making	O
this	O
less	O
of	O
an	O
issue	O
.	O
</s>
<s>
Resolution	O
and	O
frame	O
rate	O
can	O
always	O
be	O
reduced	O
to	O
conserve	O
CPU	B-Device
resources	O
.	O
</s>
<s>
FreeTrack	B-Operating_System
requires	O
the	O
tracking	O
points	O
to	O
be	O
isolated	O
from	O
all	O
other	O
light	O
;	O
this	O
is	O
best	O
done	O
using	O
infrared	O
LEDs	O
and	O
a	O
visible-light	O
blocking	O
filter	O
in	O
front	O
of	O
the	O
camera	O
.	O
</s>
<s>
Photographic	O
film	O
or	O
the	O
magnetic	B-Architecture
storage	I-Architecture
medium	O
inside	O
floppy	B-Device
disks	I-Device
can	O
be	O
used	O
as	O
inexpensive	O
visible-light	O
filters	O
.	O
</s>
<s>
All	O
video	O
devices	O
like	O
webcams	B-Protocol
have	O
a	O
built-in	O
infrared-blocking	O
filter	O
,	O
which	O
can	O
be	O
removed	O
to	O
improve	O
sensitivity	O
to	O
infrared	O
light	O
,	O
allowing	O
better	O
point	O
isolation	O
and	O
the	O
possibility	O
of	O
retroreflective	O
tracking	O
.	O
</s>
<s>
This	O
is	O
normally	O
a	O
straightforward	O
and	O
reversible	O
procedure	O
for	O
most	O
webcams	B-Protocol
.	O
</s>
<s>
Wii	B-Device
Remotes	I-Device
and	O
NaturalPoint	O
cameras	O
are	O
designed	O
for	O
infrared	O
point	O
tracking	O
,	O
so	O
they	O
already	O
have	O
visible-light-blocking	O
filters	O
.	O
</s>
<s>
Three	O
point	O
clip	O
:	O
asymmetrical	O
triangular	O
arrangement	O
of	O
points	O
that	O
can	O
be	O
clipped	O
to	O
headphones	B-Device
and	O
positioned	O
to	O
the	O
side	O
of	O
the	O
head	O
.	O
</s>
<s>
Component	O
kits	O
and	O
fully	O
constructed	O
models	O
are	O
also	O
available	O
for	O
purchase	O
from	O
some	O
members	O
of	O
the	O
FreeTrack	B-Operating_System
community	O
.	O
</s>
<s>
An	O
active	O
point	O
model	O
uses	O
visible	O
or	O
infrared	O
LEDs	O
(	O
5mm	O
or	O
larger	O
)	O
to	O
represent	O
the	O
tracking	O
points	O
,	O
powered	O
by	O
battery	O
,	O
transformer	O
(	O
plug	O
pack	O
)	O
or	O
USB	B-Protocol
.	O
</s>
<s>
Common	O
LEDs	O
,	O
like	O
those	O
found	O
in	O
remote	B-Protocol
controls	I-Protocol
,	O
have	O
a	O
narrow	O
,	O
highly	O
focused	O
beam	O
which	O
is	O
not	O
suitable	O
for	O
optical	B-Application
motion	I-Application
tracking	I-Application
.	O
</s>
<s>
In	O
most	O
cases	O
a	O
webcam	B-Protocol
’s	O
internal	O
infrared	O
blocking	O
filter	O
needs	O
to	O
be	O
removed	O
to	O
increase	O
sensitivity	O
enough	O
that	O
the	O
infrared	O
light	O
reflected	O
by	O
the	O
tracking	O
points	O
can	O
be	O
seen	O
.	O
</s>
<s>
FreeTrack	B-Operating_System
has	O
a	O
simple	O
interface	O
that	O
can	O
be	O
freely	O
used	O
by	O
third	O
party	O
programs	O
such	O
as	O
Eyeware	O
Beam	O
to	O
access	O
6DOF	O
tracking	O
data	O
,	O
both	O
real	O
raw	O
measurements	O
and	O
virtual	O
.	O
</s>
<s>
Bohemia	O
Interactive	O
's	O
ARMA	B-Application
2	I-Application
is	O
the	O
first	O
game	O
to	O
support	O
the	O
FreeTrack	B-Operating_System
interface	O
and	O
is	O
the	O
first	O
to	O
have	O
exclusive	O
support	O
.	O
</s>
<s>
FreeTrack	B-Operating_System
is	O
compatible	O
with	O
the	O
unencrypted	O
version	O
of	O
NaturalPoint	O
's	O
head	B-Application
tracking	I-Application
TrackIR	B-Operating_System
interface	O
that	O
has	O
widespread	O
support	O
in	O
simulation	O
games	O
.	O
</s>
<s>
NaturalPoint	O
have	O
been	O
supplying	O
game	O
developers	O
with	O
an	O
encrypted	O
version	O
of	O
the	O
interface	O
for	O
more	O
popular	O
titles	O
since	O
late	O
2008	O
,	O
these	O
can	O
be	O
identified	O
as	O
requiring	O
TrackIR	B-Operating_System
software	O
version	O
4.1.036	O
or	O
higher	O
and	O
are	O
incompatible	O
with	O
FreeTrack	B-Operating_System
.	O
</s>
<s>
The	O
developers	O
of	O
the	O
first	O
game	O
affected	O
,	O
DCS	B-Language
:	I-Language
Black	I-Language
Shark	I-Language
,	O
tried	O
to	O
release	O
their	O
own	O
head	B-Application
tracking	I-Application
interface	O
but	O
soon	O
after	O
canceled	O
it	O
at	O
NaturalPoint	O
's	O
request	O
.	O
</s>
<s>
FreeTrack	B-Operating_System
compatibility	O
is	O
still	O
possible	O
using	O
to	O
remove	O
the	O
encryption	O
requirement	O
in	O
games	O
.	O
</s>
<s>
TIRViews.dll	O
is	O
a	O
dynamic-link	O
library	O
file	O
distributed	O
with	O
TrackIR	B-Operating_System
software	O
that	O
provides	O
tailored	O
support	O
for	O
a	O
small	O
number	O
of	O
mostly	O
older	O
games	O
,	O
using	O
special	O
interfaces	O
or	O
memory	O
hacks	B-Architecture
to	O
facilitate	O
view	O
control	O
.	O
</s>
<s>
Though	O
a	O
violation	O
of	O
the	O
TrackIR	B-Operating_System
software	O
's	O
EULA	O
,	O
</s>
<s>
it	O
is	O
possible	O
to	O
use	O
it	O
with	O
FreeTrack	B-Operating_System
.	O
</s>
<s>
and	O
is	O
covered	O
by	O
a	O
NDA	O
,	O
so	O
while	O
FreeTrack	B-Operating_System
is	O
free	B-Application
software	I-Application
,	O
the	O
TrackIR	B-Operating_System
interface	O
component	O
is	O
required	O
to	O
be	O
closed	B-Application
source	I-Application
.	O
</s>
