<s>
Stereoscopic	B-Algorithm
depth	I-Algorithm
rendition	I-Algorithm
specifies	O
how	O
the	O
depth	O
of	O
a	O
three-dimensional	O
object	O
is	O
encoded	O
in	O
a	O
stereoscopic	B-Algorithm
reconstruction	O
.	O
</s>
<s>
A	O
stereogram	B-Algorithm
consists	O
of	O
a	O
pair	O
of	O
two-dimensional	O
frames	O
,	O
one	O
for	O
each	O
eye	O
.	O
</s>
<s>
Other	O
factors	O
,	O
however	O
,	O
contribute	O
to	O
the	O
depth	O
seen	O
in	O
a	O
stereoscopic	B-Algorithm
view	I-Algorithm
and	O
whether	O
it	O
corresponds	O
to	O
that	O
in	O
the	O
actual	O
object	O
;	O
the	O
act	O
of	O
viewing	O
a	O
stereoscopic	B-Algorithm
display	I-Algorithm
often	O
alters	O
observers	O
 '	O
three-dimensional	O
perception	O
.	O
</s>
<s>
The	O
right	O
and	O
left	O
eyes	O
 '	O
panels	O
in	O
a	O
stereoscopic	B-Algorithm
reconstruction	O
are	O
created	O
by	O
projection	O
from	O
the	O
principal	O
points	O
of	O
the	O
twin	O
recording	O
camera	O
.	O
</s>
<s>
In	O
the	O
left	O
eye	O
panel	O
of	O
the	O
stereogram	B-Algorithm
the	O
distance	O
AB	O
is	O
the	O
representation	O
of	O
the	O
front	O
face	O
of	O
the	O
cube	O
,	O
in	O
the	O
right	O
eye	O
panel	O
,	O
there	O
is	O
in	O
addition	O
BC	O
,	O
the	O
representation	O
of	O
the	O
cube	O
's	O
depth	O
,	O
i.e.	O
,	O
the	O
intercept	O
on	O
the	O
screen	O
of	O
the	O
rays	O
from	O
the	O
cameras’	O
principal	O
points	O
to	O
the	O
back	O
of	O
the	O
cube	O
.	O
</s>
<s>
(	O
To	O
simplify	O
the	O
account	O
,	O
the	O
right	O
and	O
left	O
screens	O
are	O
taken	O
to	O
be	O
superimposed	O
,	O
as	O
they	O
would	O
be	O
in	O
a	O
3D	B-Algorithm
display	I-Algorithm
with	I-Algorithm
LCD	I-Algorithm
goggles	I-Algorithm
.	O
)	O
</s>
<s>
This	O
stereogram	B-Algorithm
with	O
the	O
cube	O
,	O
whose	O
depth/width	O
ratio	O
had	O
been	O
captured	O
with	O
recording	O
parameters	O
ac	O
and	O
zc	O
and	O
embodied	O
in	O
the	O
ratio	O
BC/AB	O
=	O
rc	O
=	O
ac/zc	O
,	O
is	O
now	O
viewed	O
by	O
an	O
observer	O
with	O
interocular	O
separation	O
ao	O
at	O
a	O
distance	O
zo	O
.	O
</s>
<s>
The	O
stereoscopic	B-Algorithm
depth	I-Algorithm
rendition	I-Algorithm
r	O
is	O
a	O
measure	O
of	O
the	O
flattening	O
or	O
expansion	O
in	O
depth	O
for	O
a	O
display	O
situation	O
and	O
is	O
equal	O
to	O
the	O
ratio	O
of	O
the	O
angles	O
of	O
depth	O
and	O
width	O
subtended	O
at	O
the	O
eye	O
in	O
the	O
stereogram	B-Algorithm
reconstruction	O
of	O
a	O
small	O
cubical	O
element	O
.	O
</s>
<s>
This	O
stereogram	B-Algorithm
is	O
now	O
viewed	O
from	O
a	O
distance	O
of	O
39cm	O
(	O
the	O
magnification	O
does	O
not	O
matter	O
,	O
only	O
the	O
ratio	O
BC/AB	O
has	O
to	O
have	O
been	O
conserved	O
)	O
by	O
an	O
observer	O
with	O
interocular	O
distance	O
6.5cm	O
,	O
i.e.	O
,	O
ro	O
=	O
6.5/39	O
=	O
0.167	O
.	O
</s>
<s>
According	O
to	O
equation	O
(	O
1	O
)	O
for	O
this	O
view	O
the	O
structure	O
has	O
a	O
stereoscopic	B-Algorithm
depth	I-Algorithm
rendition	I-Algorithm
given	O
by	O
R	O
=	O
rc/ro	O
=	O
0.25/0.167	O
=	O
1.5	O
,	O
meaning	O
that	O
the	O
observer	O
is	O
presented	O
with	O
the	O
geometrical	O
situation	O
not	O
of	O
a	O
cube	O
but	O
of	O
a	O
structure	O
1.5	O
×	O
as	O
deep	O
as	O
it	O
is	O
wide	O
.	O
</s>
<s>
This	O
example	O
illustrates	O
that	O
a	O
given	O
stereoscopic	B-Algorithm
presentation	O
for	O
a	O
given	O
observer	O
gains	O
in	O
depth/width	O
ratio	O
(	O
expands	O
in	O
depth	O
)	O
with	O
increasing	O
observation	O
distance	O
.	O
</s>
<s>
This	O
particular	O
condition	O
has	O
been	O
termed	O
homeomorphic	O
by	O
Moritz	O
von	O
Rohr	O
and	O
was	O
contrasted	O
by	O
him	O
with	O
the	O
heteromorphic	O
one	O
in	O
which	O
the	O
r	O
values	O
of	O
the	O
stereoscopic	B-Algorithm
and	O
actual	O
views	O
differ	O
.	O
</s>
<s>
But	O
homeomorphic	O
rendition	O
with	O
geometrical	O
parameters	O
identical	O
to	O
the	O
original	O
does	O
not	O
assure	O
that	O
an	O
observer	O
's	O
perception	O
of	O
depth	O
in	O
a	O
stereoscopic	B-Algorithm
image	I-Algorithm
is	O
the	O
same	O
as	O
that	O
in	O
the	O
actual	O
three-dimensional	O
structure	O
.	O
</s>
<s>
In	O
contrast	O
to	O
the	O
rules	O
,	O
laid	O
out	O
above	O
,	O
for	O
calculating	O
the	O
geometrically	O
defined	O
stereoscopic	B-Algorithm
depth	I-Algorithm
rendition	I-Algorithm
,	O
the	O
perceived	O
depth	O
involves	O
factors	O
—	O
context	O
,	O
previous	O
experience	O
—	O
that	O
are	O
individual	O
and	O
not	O
specifiable	O
with	O
the	O
same	O
degree	O
of	O
generality	O
.	O
</s>
<s>
This	O
is	O
by	O
no	O
means	O
fixed	O
:	O
the	O
subjective	O
z	O
is	O
only	O
vaguely	O
related	O
to	O
the	O
actual	O
object	O
distance	O
,	O
as	O
is	O
obvious	O
in	O
watching	O
3D	B-Algorithm
film	I-Algorithm
.	O
</s>
<s>
On	O
the	O
other	O
hand	O
,	O
recent	O
research	O
confirms	O
that	O
the	O
relative	O
depths	O
seen	O
in	O
three-dimensional	O
configurations	O
scale	O
up	O
more	O
or	O
less	O
in	O
proportion	O
to	O
the	O
stereoscopic	B-Algorithm
depth	I-Algorithm
rendition	I-Algorithm
arrived	O
at	O
within	O
the	O
purely	O
geometrical	O
framework	O
.	O
</s>
