<s>
A	O
volumetric	B-Algorithm
display	I-Algorithm
device	I-Device
is	O
a	O
display	B-Device
device	I-Device
that	O
forms	O
a	O
visual	O
representation	O
of	O
an	O
object	O
in	O
three	O
physical	O
dimensions	O
,	O
as	O
opposed	O
to	O
the	O
planar	O
image	O
of	O
traditional	O
screens	O
that	O
simulate	O
depth	O
through	O
a	O
number	O
of	O
different	O
visual	O
effects	O
.	O
</s>
<s>
One	O
definition	O
offered	O
by	O
pioneers	O
in	O
the	O
field	O
is	O
that	O
volumetric	B-Algorithm
displays	I-Algorithm
create	O
3D	O
imagery	O
via	O
the	O
emission	O
,	O
scattering	O
,	O
or	O
relaying	O
of	O
illumination	O
from	O
well-defined	O
regions	O
in	O
(	O
x	O
,	O
y	O
,	O
z	O
)	O
space	O
.	O
</s>
<s>
A	O
true	O
volumetric	B-Algorithm
display	I-Algorithm
produces	O
in	O
the	O
observer	O
a	O
visual	O
experience	O
of	O
a	O
material	O
object	O
in	O
three-dimensional	O
space	O
,	O
even	O
though	O
no	O
such	O
object	O
is	O
present	O
.	O
</s>
<s>
Volumetric	B-Algorithm
3D	I-Algorithm
displays	I-Algorithm
are	O
technically	O
not	O
autostereoscopic	B-Algorithm
,	O
even	O
though	O
they	O
create	O
three-dimensional	O
imagery	O
visible	O
to	O
the	O
unaided	O
eye	O
.	O
</s>
<s>
This	O
is	O
because	O
the	O
displays	O
do	O
not	O
generate	O
stereoscopic	O
images	O
;	O
They	O
naturally	O
provide	O
focally-accurate	O
holographic	B-Algorithm
wavefronts	O
to	O
the	O
eyes	O
.	O
</s>
<s>
Due	O
to	O
this	O
,	O
they	O
have	O
accurate	O
characteristics	O
of	O
material	O
objects	O
such	O
as	O
focal	O
depth	O
,	O
motion	O
parallax	O
,	O
and	O
vergence	B-Algorithm
.	O
</s>
<s>
Volumetric	B-Algorithm
displays	I-Algorithm
are	O
one	O
of	O
several	O
kinds	O
of	O
3D	B-Algorithm
displays	I-Algorithm
.	O
</s>
<s>
Other	O
types	O
are	O
stereoscopes	B-Algorithm
,	O
view-sequential	O
displays	O
,	O
electro-holographic	O
displays	O
,	O
"	O
two	O
view	O
"	O
displays	O
,	O
and	O
panoramagrams	O
.	O
</s>
<s>
Although	O
first	O
postulated	O
in	O
1912	O
,	O
and	O
a	O
staple	O
of	O
science	O
fiction	O
,	O
volumetric	B-Algorithm
displays	I-Algorithm
are	O
still	O
not	O
widely	O
used	O
in	O
everyday	O
life	O
.	O
</s>
<s>
There	O
are	O
numerous	O
potential	O
markets	O
for	O
volumetric	B-Algorithm
displays	I-Algorithm
with	O
use	O
cases	O
including	O
medical	O
imaging	O
,	O
mining	O
,	O
education	O
,	O
advertising	O
,	O
simulation	O
,	O
video	O
games	O
,	O
communication	O
and	O
geophysical	O
visualisation	O
.	O
</s>
<s>
When	O
compared	O
to	O
other	O
3D	O
visualisation	O
tools	O
such	O
as	O
virtual	B-Application
reality	I-Application
,	O
volumetric	B-Algorithm
displays	I-Algorithm
offer	O
an	O
inherently	O
different	O
mode	O
of	O
interaction	O
,	O
providing	O
the	O
opportunity	O
for	O
a	O
group	O
of	O
people	O
to	O
gather	O
around	O
the	O
display	O
and	O
interact	O
in	O
a	O
natural	O
manner	O
without	O
having	O
to	O
don	O
3D	O
glasses	O
or	O
other	O
head	O
gear	O
.	O
</s>
<s>
There	O
is	O
no	O
officially	O
accepted	O
"	O
taxonomy	O
"	O
of	O
the	O
variety	O
of	O
volumetric	B-Algorithm
displays	I-Algorithm
,	O
an	O
issue	O
which	O
is	O
complicated	O
by	O
the	O
many	O
permutations	B-Algorithm
of	O
their	O
characteristics	O
.	O
</s>
<s>
For	O
example	O
,	O
illumination	O
within	O
a	O
volumetric	B-Algorithm
display	I-Algorithm
can	O
either	O
reach	O
the	O
eye	O
directly	O
from	O
the	O
source	O
or	O
via	O
an	O
intermediate	O
surface	O
such	O
as	O
a	O
mirror	O
or	O
glass	O
;	O
likewise	O
,	O
this	O
surface	O
,	O
which	O
need	O
not	O
be	O
tangible	O
,	O
can	O
undergo	O
motion	O
such	O
as	O
oscillation	O
or	O
rotation	O
.	O
</s>
<s>
Swept-surface	O
(	O
or	O
"	O
swept-volume	O
"	O
)	O
volumetric	B-Algorithm
3D	I-Algorithm
displays	I-Algorithm
rely	O
on	O
the	O
human	O
persistence	O
of	O
vision	O
to	O
fuse	O
a	O
series	O
of	O
slices	O
of	O
the	O
3D	O
object	O
into	O
a	O
single	O
3D	O
image	O
.	O
</s>
<s>
Another	O
type	O
of	O
3D	B-Algorithm
display	I-Algorithm
that	O
is	O
a	O
candidate	O
member	O
of	O
the	O
class	O
of	O
swept-volume	O
3D	B-Algorithm
displays	I-Algorithm
is	O
the	O
varifocal	O
mirror	O
architecture	O
.	O
</s>
<s>
This	O
display	O
has	O
a	O
volume	O
area	O
that	O
is	O
18cm	O
*	O
18cm	O
*	O
8cm	O
deep	O
and	O
can	O
render	O
up	O
to	O
500	O
million	O
voxels	B-Algorithm
per	O
second	O
.	O
</s>
<s>
So-called	O
"	O
static-volume	O
"	O
volumetric	B-Algorithm
3D	I-Algorithm
displays	I-Algorithm
create	O
imagery	O
without	O
any	O
macroscopic	O
moving	O
parts	O
in	O
the	O
image	O
volume	O
.	O
</s>
<s>
This	O
is	O
probably	O
the	O
most	O
"	O
direct	O
"	O
form	O
of	O
volumetric	B-Algorithm
display	I-Algorithm
.	O
</s>
<s>
When	O
the	O
elements	O
(	O
called	O
voxels	B-Algorithm
)	O
are	O
activated	O
,	O
they	O
show	O
a	O
solid	O
pattern	O
within	O
the	O
space	O
of	O
the	O
display	O
.	O
</s>
<s>
Several	O
static-volume	O
volumetric	B-Algorithm
3D	I-Algorithm
displays	I-Algorithm
use	O
laser	O
light	O
to	O
encourage	O
visible	O
radiation	O
in	O
a	O
solid	O
,	O
liquid	O
,	O
or	O
gas	O
.	O
</s>
<s>
For	O
example	O
,	O
some	O
researchers	O
have	O
relied	O
on	O
two-step	O
upconversion	O
within	O
a	O
rare-earth-doped	O
material	O
when	O
illuminated	O
by	O
intersecting	O
infrared	O
laser	O
beams	O
of	O
the	O
appropriate	O
frequencies	O
.	O
</s>
<s>
For	O
instance	O
,	O
a	O
fog	B-General_Concept
display	I-General_Concept
using	O
multiple	O
projectors	O
can	O
render	O
a	O
3D	O
image	O
in	O
a	O
volume	O
of	O
space	O
,	O
resulting	O
in	O
a	O
static-volume	O
volumetric	B-Algorithm
display	I-Algorithm
.	O
</s>
<s>
The	O
technique	O
bypasses	O
the	O
need	O
to	O
use	O
high-powered	O
lasers	O
and	O
the	O
generation	O
of	O
plasma	O
,	O
which	O
alleviates	O
concerns	O
for	O
safety	O
and	O
dramatically	O
improves	O
the	O
accessibility	O
of	O
the	O
three-dimensional	B-Algorithm
displays	I-Algorithm
.	O
</s>
<s>
UV-light	O
and	O
green-light	O
patterns	O
are	O
aimed	O
at	O
the	O
dye	O
solution	O
,	O
which	O
initiates	O
photoactivation	O
and	O
thus	O
creates	O
the	O
"	O
on	O
"	O
voxel	B-Algorithm
.	O
</s>
<s>
The	O
device	O
is	O
capable	O
of	O
displaying	O
a	O
minimal	O
voxel	B-Algorithm
size	O
of	O
0.68mm3	O
,	O
with	O
200μm	O
resolution	O
,	O
and	O
good	O
stability	O
over	O
hundreds	O
of	O
on	O
–	O
off	O
cycles	O
.	O
</s>
<s>
The	O
unique	O
properties	O
of	O
volumetric	B-Algorithm
displays	I-Algorithm
,	O
which	O
may	O
include	O
360-degree	O
viewing	O
,	O
agreement	O
of	O
vergence	B-Algorithm
and	O
accommodation	O
cues	O
,	O
and	O
their	O
inherent	O
"	O
three-dimensionality	O
"	O
,	O
enable	O
new	O
user	B-Application
interface	I-Application
techniques	I-Application
.	O
</s>
<s>
There	O
is	O
recent	O
work	O
investigating	O
the	O
speed	O
and	O
accuracy	O
benefits	O
of	O
volumetric	B-Algorithm
displays	I-Algorithm
,	O
new	O
graphical	O
user	O
interfaces	O
,	O
and	O
medical	O
applications	O
enhanced	O
by	O
volumetric	B-Algorithm
displays	I-Algorithm
.	O
</s>
<s>
Also	O
,	O
software	O
platforms	O
exist	O
that	O
deliver	O
native	O
and	O
legacy	O
2D	O
and	O
3D	O
content	O
to	O
volumetric	B-Algorithm
displays	I-Algorithm
.	O
</s>
<s>
An	O
artform	O
called	O
Hologlyphics	O
has	O
been	O
explored	O
since	O
1994	O
,	O
combining	O
elements	O
of	O
holography	B-Algorithm
,	O
music	O
,	O
video	O
synthesis	O
,	O
visionary	O
film	O
,	O
sculpture	O
and	O
improvisation	O
.	O
</s>
<s>
Known	O
volumetric	B-Algorithm
display	I-Algorithm
technologies	O
also	O
have	O
several	O
drawbacks	O
that	O
are	O
exhibited	O
depending	O
on	O
trade-offs	O
chosen	O
by	O
the	O
system	O
designer	O
.	O
</s>
<s>
It	O
is	O
often	O
claimed	O
that	O
volumetric	B-Algorithm
displays	I-Algorithm
are	O
incapable	O
of	O
reconstructing	O
scenes	O
with	O
viewer-position-dependent	O
effects	O
,	O
such	O
as	O
occlusion	O
and	O
opacity	O
.	O
</s>
<s>
This	O
is	O
a	O
misconception	O
;	O
a	O
display	O
whose	O
voxels	B-Algorithm
have	O
non-isotropic	O
radiation	O
profiles	O
are	O
indeed	O
able	O
to	O
depict	O
position-dependent	O
effects	O
.	O
</s>
<s>
To-date	O
,	O
occlusion-capable	O
volumetric	B-Algorithm
displays	I-Algorithm
require	O
two	O
conditions	O
:	O
(	O
1	O
)	O
the	O
imagery	O
is	O
rendered	O
and	O
projected	O
as	O
a	O
series	O
of	O
"	O
views	O
,	O
"	O
rather	O
than	O
"	O
slices	O
,	O
"	O
and	O
(	O
2	O
)	O
the	O
time-varying	O
image	O
surface	O
is	O
not	O
a	O
uniform	O
diffuser	O
.	O
</s>
<s>
For	O
example	O
,	O
researchers	O
have	O
demonstrated	O
spinning-screen	O
volumetric	B-Algorithm
displays	I-Algorithm
with	O
reflective	O
and/or	O
vertically	O
diffuse	O
screens	O
whose	O
imagery	O
exhibits	O
occlusion	O
and	O
opacity	O
.	O
</s>
<s>
One	O
other	O
consideration	O
is	O
the	O
very	O
large	O
amount	O
of	O
bandwidth	O
required	O
to	O
feed	O
imagery	O
to	O
a	O
volumetric	B-Algorithm
display	I-Algorithm
.	O
</s>
<s>
For	O
example	O
,	O
a	O
standard	O
24	O
bits	O
per	O
pixel	O
,	O
1024×768	O
resolution	O
,	O
flat/2D	O
display	O
requires	O
about	O
135	O
MB/s	O
to	O
be	O
sent	O
to	O
the	O
display	O
hardware	O
to	O
sustain	O
60	O
frames	O
per	O
second	O
,	O
whereas	O
a	O
24	O
bits	O
per	O
voxel	B-Algorithm
,	O
1024×768×1024	O
(	O
1024	O
"	O
pixel	O
layers	O
"	O
in	O
the	O
Z	O
axis	O
)	O
volumetric	B-Algorithm
display	I-Algorithm
would	O
need	O
to	O
send	O
about	O
three	O
orders	O
of	O
magnitude	O
more	O
(	O
135	O
GB/s	O
)	O
to	O
the	O
display	O
hardware	O
to	O
sustain	O
60	O
volumes	O
per	O
second	O
.	O
</s>
<s>
Furthermore	O
,	O
a	O
3D	O
volumetric	B-Algorithm
display	I-Algorithm
would	O
require	O
two	O
to	O
three	O
orders	O
of	O
magnitude	O
more	O
CPU	B-Device
and/or	O
GPU	B-Architecture
power	O
beyond	O
that	O
necessary	O
for	O
2D	O
imagery	O
of	O
equivalent	O
quality	O
,	O
due	O
at	O
least	O
in	O
part	O
to	O
the	O
sheer	O
amount	O
of	O
data	O
that	O
must	O
be	O
created	O
and	O
sent	O
to	O
the	O
display	O
hardware	O
.	O
</s>
<s>
However	O
,	O
if	O
only	O
the	O
outer	O
surface	O
of	O
the	O
volume	O
is	O
visible	O
,	O
the	O
number	O
of	O
voxels	B-Algorithm
required	O
would	O
be	O
of	O
the	O
same	O
order	O
as	O
the	O
number	O
of	O
pixels	O
on	O
a	O
conventional	O
display	O
.	O
</s>
<s>
This	O
would	O
only	O
be	O
the	O
case	O
if	O
the	O
voxels	B-Algorithm
do	O
not	O
have	O
"	O
alpha	O
"	O
or	O
transparency	O
values	O
.	O
</s>
