<s>
The	O
condensation	B-General_Concept
algorithm	I-General_Concept
(	O
Conditional	O
Density	O
Propagation	O
)	O
is	O
a	O
computer	B-Application
vision	I-Application
algorithm	O
.	O
</s>
<s>
The	O
principal	O
application	O
is	O
to	O
detect	O
and	O
track	B-Operating_System
the	O
contour	O
of	O
objects	O
moving	O
in	O
a	O
cluttered	O
environment	O
.	O
</s>
<s>
Object	O
tracking	O
is	O
one	O
of	O
the	O
more	O
basic	O
and	O
difficult	O
aspects	O
of	O
computer	B-Application
vision	I-Application
and	O
is	O
generally	O
a	O
prerequisite	O
to	O
object	O
recognition	O
.	O
</s>
<s>
Condensation	O
is	O
a	O
probabilistic	B-General_Concept
algorithm	I-General_Concept
that	O
attempts	O
to	O
solve	O
this	O
problem	O
.	O
</s>
<s>
The	O
algorithm	O
itself	O
is	O
described	O
in	O
detail	O
by	O
Isard	O
and	O
Blake	O
in	O
a	O
publication	O
in	O
the	O
International	O
Journal	O
of	O
Computer	B-Application
Vision	I-Application
in	O
1998	O
.	O
</s>
<s>
The	O
original	O
part	O
of	O
this	O
work	O
is	O
the	O
application	O
of	O
particle	B-Algorithm
filter	I-Algorithm
estimation	O
techniques	O
.	O
</s>
<s>
The	O
condensation	B-General_Concept
algorithm	I-General_Concept
in	O
its	O
most	O
general	O
form	O
requires	O
no	O
assumptions	O
about	O
the	O
probability	O
distributions	O
of	O
the	O
object	O
or	O
measurements	O
.	O
</s>
<s>
The	O
condensation	B-General_Concept
algorithm	I-General_Concept
seeks	O
to	O
solve	O
the	O
problem	O
of	O
estimating	O
the	O
conformation	O
of	O
an	O
object	O
described	O
by	O
a	O
vector	O
at	O
time	O
,	O
given	O
observations	O
of	O
the	O
detected	O
features	O
in	O
the	O
images	O
up	O
to	O
and	O
including	O
the	O
current	O
time	O
.	O
</s>
<s>
conditional	O
probability	O
density	O
by	O
applying	O
a	O
nonlinear	O
filter	O
based	O
on	O
factored	O
sampling	O
and	O
can	O
be	O
thought	O
of	O
as	O
a	O
development	O
of	O
a	O
Monte-Carlo	B-Algorithm
method	I-Algorithm
.	O
</s>
<s>
The	O
condensation	B-General_Concept
algorithm	I-General_Concept
is	O
a	O
generative	O
model	O
since	O
it	O
models	O
the	O
joint	O
distribution	O
of	O
the	O
object	O
and	O
the	O
observer	O
.	O
</s>
<s>
independent	O
of	O
each	O
other	O
and	O
the	O
dynamics	O
facilitate	O
the	O
implementation	O
of	O
the	O
condensation	B-General_Concept
algorithm	I-General_Concept
.	O
</s>
<s>
The	O
condensation	B-General_Concept
algorithm	I-General_Concept
is	O
relatively	O
simple	O
when	O
compared	O
to	O
the	O
computational	O
intensity	O
of	O
the	O
Ricatti	O
equation	O
required	O
for	O
Kalman	O
filtering	O
.	O
</s>
<s>
The	O
model	O
used	O
by	O
Isard	O
1998	O
is	O
a	O
linear	O
parameterization	O
of	O
B-splines	B-Algorithm
in	O
which	O
the	O
splines	O
are	O
limited	O
to	O
certain	O
configurations	O
.	O
</s>
<s>
Suitable	O
configurations	O
were	O
found	O
by	O
analytically	O
determining	O
combinations	O
of	O
contours	O
from	O
multiple	O
views	O
,	O
of	O
the	O
object	O
in	O
different	O
poses	O
,	O
and	O
through	O
principal	B-Application
component	I-Application
analysis	I-Application
(	O
PCA	O
)	O
on	O
the	O
deforming	O
object	O
.	O
</s>
<s>
Isard	O
1998	O
assumes	O
that	O
the	O
clutter	O
which	O
may	O
make	O
the	O
object	O
not	O
visible	O
is	O
a	O
Poisson	O
random	O
process	O
with	O
spatial	O
density	O
and	O
that	O
any	O
true	O
target	O
measurement	O
is	O
unbiased	O
and	O
normally	O
distributed	O
with	O
standard	B-General_Concept
deviation	I-General_Concept
.	O
</s>
<s>
The	O
basic	O
condensation	B-General_Concept
algorithm	I-General_Concept
is	O
used	O
to	O
track	B-Operating_System
a	O
single	O
object	O
in	O
time	O
.	O
</s>
<s>
It	O
is	O
possible	O
to	O
extend	O
the	O
condensation	B-General_Concept
algorithm	I-General_Concept
using	O
a	O
single	O
probability	O
distribution	O
to	O
describe	O
the	O
likely	O
states	O
of	O
multiple	O
objects	O
to	O
track	B-Operating_System
multiple	O
objects	O
in	O
a	O
scene	O
at	O
the	O
same	O
time	O
.	O
</s>
<s>
The	O
algorithm	O
can	O
be	O
used	O
for	O
vision-based	O
robot	B-General_Concept
localization	I-General_Concept
of	O
mobile	O
robots	O
.	O
</s>
<s>
Extensions	O
of	O
the	O
condensation	B-General_Concept
algorithm	I-General_Concept
have	O
also	O
been	O
used	O
to	O
recognize	B-General_Concept
human	I-General_Concept
gestures	I-General_Concept
in	O
image	O
sequences	O
.	O
</s>
<s>
This	O
application	O
of	O
the	O
condensation	B-General_Concept
algorithm	I-General_Concept
impacts	O
the	O
range	O
of	O
human	O
–	O
computer	O
interactions	O
possible	O
.	O
</s>
<s>
The	O
condensation	B-General_Concept
algorithm	I-General_Concept
has	O
also	O
been	O
used	O
for	O
face	O
recognition	O
in	O
a	O
video	O
sequence	O
.	O
</s>
<s>
An	O
implementation	O
of	O
the	O
condensation	B-General_Concept
algorithm	I-General_Concept
in	O
C	B-Language
can	O
be	O
found	O
on	O
.	O
</s>
<s>
An	O
implementation	O
in	O
MATLAB	B-Language
can	O
be	O
found	O
on	O
the	O
.	O
</s>
<s>
An	O
example	O
of	O
implementation	O
using	O
the	O
OpenCV	B-Language
library	O
can	O
be	O
found	O
on	O
the	O
.	O
</s>
