<s>
A	O
scene	B-Data_Structure
graph	I-Data_Structure
is	O
a	O
general	O
data	B-General_Concept
structure	I-General_Concept
commonly	O
used	O
by	O
vector-based	O
graphics	O
editing	O
applications	O
and	O
modern	O
computer	O
games	O
,	O
which	O
arranges	O
the	O
logical	O
and	O
often	O
spatial	O
representation	O
of	O
a	O
graphical	O
scene	O
.	O
</s>
<s>
It	O
is	O
a	O
collection	O
of	O
nodes	O
in	O
a	O
graph	B-Application
or	O
tree	B-Application
structure	O
.	O
</s>
<s>
A	O
tree	B-Application
node	O
may	O
have	O
many	O
children	O
but	O
only	O
a	O
single	O
parent	O
,	O
with	O
the	O
effect	O
of	O
a	O
parent	O
applied	O
to	O
all	O
its	O
child	O
nodes	O
;	O
an	O
operation	O
performed	O
on	O
a	O
group	O
automatically	O
propagates	O
its	O
effect	O
to	O
all	O
of	O
its	O
members	O
.	O
</s>
<s>
In	O
many	O
programs	O
,	O
associating	O
a	O
geometrical	O
transformation	B-Algorithm
matrix	I-Algorithm
(	O
see	O
also	O
transformation	B-Algorithm
and	O
matrix	B-Architecture
)	O
at	O
each	O
group	O
level	O
and	O
concatenating	O
such	O
matrices	O
together	O
is	O
an	O
efficient	O
and	O
natural	O
way	O
to	O
process	O
such	O
operations	O
.	O
</s>
<s>
In	O
vector-based	O
graphics	O
editing	O
,	O
each	O
leaf	B-Data_Structure
node	I-Data_Structure
in	O
a	O
scene	B-Data_Structure
graph	I-Data_Structure
represents	O
some	O
atomic	O
unit	O
of	O
the	O
document	O
,	O
usually	O
a	O
shape	O
such	O
as	O
an	O
ellipse	O
or	O
Bezier	O
path	O
.	O
</s>
<s>
Although	O
shapes	O
themselves	O
(	O
particularly	O
paths	O
)	O
can	O
be	O
decomposed	O
further	O
into	O
nodes	O
such	O
as	O
spline	B-Algorithm
nodes	I-Algorithm
,	O
it	O
is	O
practical	O
to	O
think	O
of	O
the	O
scene	B-Data_Structure
graph	I-Data_Structure
as	O
composed	O
of	O
shapes	O
rather	O
than	O
going	O
to	O
a	O
lower	O
level	O
of	O
representation	O
.	O
</s>
<s>
Internally	O
,	O
there	O
may	O
be	O
no	O
real	O
structural	O
difference	O
between	O
layers	O
and	O
groups	O
at	O
all	O
,	O
since	O
they	O
are	O
both	O
just	O
nodes	O
of	O
a	O
scene	B-Data_Structure
graph	I-Data_Structure
.	O
</s>
<s>
If	O
differences	O
are	O
needed	O
,	O
a	O
common	O
type	O
declaration	O
in	O
C++	B-Language
would	O
be	O
to	O
make	O
a	O
generic	O
node	O
class	O
,	O
and	O
then	O
derive	O
layers	O
and	O
groups	O
as	O
subclasses	O
.	O
</s>
<s>
Scene	B-Data_Structure
graphs	I-Data_Structure
are	O
useful	O
for	O
modern	O
games	O
using	O
3D	O
graphics	O
and	O
increasingly	O
large	O
worlds	O
or	O
levels	O
.	O
</s>
<s>
In	O
such	O
applications	O
,	O
nodes	O
in	O
a	O
scene	B-Data_Structure
graph	I-Data_Structure
(	O
generally	O
)	O
represent	O
entities	O
or	O
objects	O
in	O
the	O
scene	O
.	O
</s>
<s>
The	O
scene	B-Data_Structure
graph	I-Data_Structure
would	O
have	O
a	O
'	O
horse	O
 '	O
node	O
with	O
a	O
'	O
knight	O
 '	O
node	O
attached	O
to	O
it	O
.	O
</s>
<s>
The	O
scene	B-Data_Structure
graph	I-Data_Structure
may	O
also	O
describe	O
the	O
spatial	O
,	O
as	O
well	O
as	O
the	O
logical	O
,	O
relationship	O
of	O
the	O
various	O
entities	O
:	O
the	O
knight	O
moves	O
through	O
3D	O
space	O
as	O
the	O
horse	O
moves	O
.	O
</s>
<s>
In	O
these	O
large	O
applications	O
,	O
memory	O
requirements	O
are	O
major	O
considerations	O
when	O
designing	O
a	O
scene	B-Data_Structure
graph	I-Data_Structure
.	O
</s>
<s>
For	O
this	O
reason	O
,	O
many	O
large	O
scene	B-Data_Structure
graph	I-Data_Structure
systems	O
use	O
geometry	B-General_Concept
instancing	I-General_Concept
to	O
reduce	O
memory	O
costs	O
and	O
increase	O
speed	O
.	O
</s>
<s>
This	O
means	O
that	O
only	O
a	O
single	O
copy	O
of	O
the	O
data	O
is	O
kept	O
,	O
which	O
is	O
then	O
referenced	O
by	O
any	O
'	O
knight	O
 '	O
nodes	O
in	O
the	O
scene	B-Data_Structure
graph	I-Data_Structure
.	O
</s>
<s>
The	O
simplest	O
form	O
of	O
scene	B-Data_Structure
graph	I-Data_Structure
uses	O
an	O
array	B-Data_Structure
or	O
linked	B-Data_Structure
list	I-Data_Structure
data	B-General_Concept
structure	I-General_Concept
,	O
and	O
displaying	O
its	O
shapes	O
is	O
simply	O
a	O
matter	O
of	O
linearly	O
iterating	O
the	O
nodes	O
one	O
by	O
one	O
.	O
</s>
<s>
Other	O
common	O
operations	O
,	O
such	O
as	O
checking	O
to	O
see	O
which	B-Data_Structure
shape	I-Data_Structure
intersects	I-Data_Structure
the	I-Data_Structure
mouse	I-Data_Structure
pointer	I-Data_Structure
are	O
also	O
done	O
via	O
linear	O
searches	O
.	O
</s>
<s>
For	O
small	O
scene	B-Data_Structure
graphs	I-Data_Structure
,	O
this	O
tends	O
to	O
suffice	O
.	O
</s>
<s>
Applying	O
an	O
operation	O
on	O
a	O
scene	B-Data_Structure
graph	I-Data_Structure
requires	O
some	O
way	O
of	O
dispatching	O
an	O
operation	O
based	O
on	O
a	O
node	O
's	O
type	O
.	O
</s>
<s>
For	O
example	O
,	O
in	O
a	O
render	O
operation	O
,	O
a	O
transformation	B-Algorithm
group	O
node	O
would	O
accumulate	O
its	O
transformation	B-Algorithm
by	O
matrix	B-Architecture
multiplication	O
,	O
vector	O
displacement	O
,	O
quaternions	O
or	O
Euler	O
angles	O
.	O
</s>
<s>
After	O
which	O
a	O
leaf	B-Data_Structure
node	I-Data_Structure
sends	O
the	O
object	O
off	O
for	O
rendering	B-Algorithm
to	O
the	O
renderer	O
.	O
</s>
<s>
Some	O
implementations	O
might	O
render	O
the	O
object	O
directly	O
,	O
which	O
invokes	O
the	O
underlying	O
rendering	B-Algorithm
API	B-General_Concept
,	O
such	O
as	O
DirectX	B-Application
or	O
OpenGL	B-Application
.	O
</s>
<s>
But	O
since	O
the	O
underlying	O
implementation	O
of	O
the	O
rendering	B-Algorithm
API	B-General_Concept
usually	O
lacks	O
portability	O
,	O
one	O
might	O
separate	O
the	O
scene	B-Data_Structure
graph	I-Data_Structure
and	O
rendering	B-Algorithm
systems	O
instead	O
.	O
</s>
<s>
In	O
object-oriented	O
languages	O
such	O
as	O
C++	B-Language
,	O
this	O
can	O
easily	O
be	O
achieved	O
by	O
virtual	B-Application
functions	I-Application
,	O
where	O
each	O
represents	O
an	O
operation	O
that	O
can	O
be	O
performed	O
on	O
a	O
node	O
.	O
</s>
<s>
Virtual	B-Application
functions	I-Application
are	O
simple	O
to	O
write	O
,	O
but	O
it	O
is	O
usually	O
impossible	O
to	O
add	O
new	O
operations	O
to	O
nodes	O
without	O
access	O
to	O
the	O
source	O
code	O
.	O
</s>
<s>
Alternatively	O
,	O
the	O
visitor	B-Language
pattern	I-Language
can	O
be	O
used	O
.	O
</s>
<s>
Other	O
techniques	O
involve	O
the	O
use	O
of	O
RTTI	B-Application
(	O
Run-Time	B-Application
Type	I-Application
Information	I-Application
)	O
.	O
</s>
<s>
The	O
operation	O
can	O
be	O
realised	O
as	O
a	O
class	O
that	O
is	O
passed	O
to	O
the	O
current	O
node	O
;	O
it	O
then	O
queries	O
the	O
node	O
's	O
type	O
using	O
RTTI	B-Application
and	O
looks	O
up	O
the	O
correct	O
operation	O
in	O
an	O
array	B-Data_Structure
of	O
callbacks	O
or	O
functors	B-Language
.	O
</s>
<s>
This	O
requires	O
that	O
the	O
map	O
of	O
types	O
to	O
callbacks	O
or	O
functors	B-Language
be	O
initialized	O
at	B-Library
runtime	I-Library
,	O
but	O
offers	O
more	O
flexibility	O
,	O
speed	O
and	O
extensibility	O
.	O
</s>
<s>
One	O
alternative	O
is	O
scene	B-Data_Structure
graph	I-Data_Structure
rebuilding	O
,	O
where	O
the	O
scene	B-Data_Structure
graph	I-Data_Structure
is	O
rebuilt	O
for	O
each	O
of	O
the	O
operations	O
performed	O
.	O
</s>
<s>
This	O
,	O
however	O
,	O
can	O
be	O
very	O
slow	O
,	O
but	O
produces	O
a	O
highly	O
optimised	O
scene	B-Data_Structure
graph	I-Data_Structure
.	O
</s>
<s>
It	O
demonstrates	O
that	O
a	O
good	O
scene	B-Data_Structure
graph	I-Data_Structure
implementation	O
depends	O
heavily	O
on	O
the	O
application	O
in	O
which	O
it	O
is	O
used	O
.	O
</s>
<s>
Traversals	B-Algorithm
are	O
the	O
key	O
to	O
the	O
power	O
of	O
applying	O
operations	O
to	O
scene	B-Data_Structure
graphs	I-Data_Structure
.	O
</s>
<s>
A	O
traversal	O
generally	O
consists	O
of	O
starting	O
at	O
some	O
arbitrary	O
node	O
(	O
often	O
the	O
root	O
of	O
the	O
scene	B-Data_Structure
graph	I-Data_Structure
)	O
,	O
applying	O
the	O
operation(s )	O
(	O
often	O
the	O
updating	O
and	O
rendering	B-Algorithm
operations	O
are	O
applied	O
one	O
after	O
the	O
other	O
)	O
,	O
and	O
recursively	O
moving	O
down	O
the	O
scene	B-Data_Structure
graph	I-Data_Structure
(	O
tree	B-Application
)	O
to	O
the	O
child	O
nodes	O
,	O
until	O
a	O
leaf	B-Data_Structure
node	I-Data_Structure
is	O
reached	O
.	O
</s>
<s>
At	O
this	O
point	O
,	O
many	O
scene	B-Data_Structure
graph	I-Data_Structure
engines	O
then	O
traverse	O
back	O
up	O
the	O
tree	B-Application
,	O
applying	O
a	O
similar	O
operation	O
.	O
</s>
<s>
For	O
example	O
,	O
consider	O
a	O
render	O
operation	O
that	O
takes	O
transformations	O
into	O
account	O
:	O
while	O
recursively	O
traversing	O
down	O
the	O
scene	B-Data_Structure
graph	I-Data_Structure
hierarchy	O
,	O
a	O
pre-render	O
operation	O
is	O
called	O
.	O
</s>
<s>
If	O
the	O
node	O
is	O
a	O
transformation	B-Algorithm
node	O
,	O
it	O
adds	O
its	O
own	O
transformation	B-Algorithm
to	O
the	O
current	O
transformation	B-Algorithm
matrix	I-Algorithm
.	O
</s>
<s>
Once	O
the	O
operation	O
finishes	O
traversing	O
all	O
the	O
children	O
of	O
a	O
node	O
,	O
it	O
calls	O
the	O
node	O
's	O
post-render	O
operation	O
so	O
that	O
the	O
transformation	B-Algorithm
node	O
can	O
undo	O
the	O
transformation	B-Algorithm
.	O
</s>
<s>
This	O
approach	O
drastically	O
reduces	O
the	O
necessary	O
amount	O
of	O
matrix	B-Architecture
multiplication	O
.	O
</s>
<s>
Some	O
scene	B-Data_Structure
graph	I-Data_Structure
operations	O
are	O
actually	O
more	O
efficient	O
when	O
nodes	O
are	O
traversed	O
in	O
a	O
different	O
order	O
–	O
this	O
is	O
where	O
some	O
systems	O
implement	O
scene	B-Data_Structure
graph	I-Data_Structure
rebuilding	O
to	O
reorder	O
the	O
scene	B-Data_Structure
graph	I-Data_Structure
into	O
an	O
easier-to-parse	O
format	O
or	O
tree	B-Application
.	O
</s>
<s>
For	O
example	O
,	O
in	O
2D	O
cases	O
,	O
scene	B-Data_Structure
graphs	I-Data_Structure
typically	O
render	O
themselves	O
by	O
starting	O
at	O
the	O
tree	B-Application
's	O
root	B-Application
node	I-Application
and	O
then	O
recursively	O
draw	O
the	O
child	O
nodes	O
.	O
</s>
<s>
The	O
tree	B-Application
's	O
leaves	O
represent	O
the	O
most	O
foreground	O
objects	O
.	O
</s>
<s>
Since	O
drawing	O
proceeds	O
from	O
back	O
to	O
front	O
with	O
closer	O
objects	O
simply	O
overwriting	O
farther	O
ones	O
,	O
the	O
process	O
is	O
known	O
as	O
employing	O
the	O
Painter	B-Algorithm
's	I-Algorithm
algorithm	I-Algorithm
.	O
</s>
<s>
Bounding	B-Data_Structure
Volume	I-Data_Structure
Hierarchies	I-Data_Structure
(	O
BVHs	O
)	O
are	O
useful	O
for	O
numerous	O
tasks	O
–	O
including	O
efficient	O
culling	O
and	O
speeding	O
up	O
collision	O
detection	O
between	O
objects	O
.	O
</s>
<s>
A	O
BVH	O
is	O
a	O
spatial	O
structure	O
,	O
but	O
does	O
n't	O
have	O
to	O
partition	O
the	O
geometry	O
(	O
see	O
spatial	B-Algorithm
partitioning	I-Algorithm
below	O
)	O
.	O
</s>
<s>
A	O
BVH	O
is	O
a	O
tree	B-Application
of	O
bounding	B-Algorithm
volumes	I-Algorithm
(	O
often	O
spheres	O
,	O
axis-aligned	B-Algorithm
bounding	I-Algorithm
boxes	I-Algorithm
or	O
oriented	B-Algorithm
bounding	I-Algorithm
boxes	I-Algorithm
)	O
.	O
</s>
<s>
At	O
the	O
root	O
of	O
the	O
tree	B-Application
is	O
a	O
volume	O
that	O
encompasses	O
all	O
the	O
volumes	O
in	O
the	O
tree	B-Application
(	O
the	O
whole	O
scene	O
)	O
.	O
</s>
<s>
If	O
an	O
object	O
's	O
bounding	B-Algorithm
volume	I-Algorithm
does	O
not	O
intersect	O
a	O
volume	O
higher	O
in	O
the	O
tree	B-Application
,	O
it	O
cannot	O
intersect	O
any	O
object	O
below	O
that	O
node	O
(	O
so	O
they	O
are	O
all	O
rejected	O
very	O
quickly	O
)	O
.	O
</s>
<s>
There	O
are	O
some	O
similarities	O
between	O
BVHs	O
and	O
scene	B-Data_Structure
graphs	I-Data_Structure
.	O
</s>
<s>
A	O
scene	B-Data_Structure
graph	I-Data_Structure
can	O
easily	O
be	O
adapted	O
to	O
include/become	O
a	O
BVH	O
–	O
if	O
each	O
node	O
has	O
a	O
volume	O
associated	O
or	O
there	O
is	O
a	O
purpose-built	O
"	O
bound	O
node	O
"	O
added	O
in	O
at	O
convenient	O
location	O
in	O
the	O
hierarchy	O
.	O
</s>
<s>
This	O
may	O
not	O
be	O
the	O
typical	O
view	O
of	O
a	O
scene	B-Data_Structure
graph	I-Data_Structure
,	O
but	O
there	O
are	O
benefits	O
to	O
including	O
a	O
BVH	O
in	O
a	O
scene	B-Data_Structure
graph	I-Data_Structure
.	O
</s>
<s>
An	O
effective	O
way	O
of	O
combining	O
spatial	B-Algorithm
partitioning	I-Algorithm
and	O
scene	B-Data_Structure
graphs	I-Data_Structure
is	O
by	O
creating	O
a	O
scene	O
leaf	B-Data_Structure
node	I-Data_Structure
that	O
contains	O
the	O
spatial	B-Algorithm
partitioning	I-Algorithm
data	O
.	O
</s>
<s>
This	O
can	O
increase	O
computational	O
efficiency	O
of	O
rendering	B-Algorithm
.	O
</s>
<s>
Some	O
systems	O
may	O
have	O
the	O
systems	O
and	O
their	O
rendering	B-Algorithm
separately	O
.	O
</s>
<s>
In	O
particular	O
,	O
it	O
is	O
bad	O
to	O
have	O
the	O
scene	B-Data_Structure
graph	I-Data_Structure
contained	O
within	O
the	O
spatial	B-Algorithm
partitioning	I-Algorithm
system	O
,	O
as	O
the	O
scene	B-Data_Structure
graph	I-Data_Structure
is	O
better	O
thought	O
of	O
as	O
the	O
grander	O
system	O
to	O
the	O
spatial	B-Algorithm
partitioning	I-Algorithm
.	O
</s>
<s>
Very	O
large	O
drawings	O
,	O
or	O
scene	B-Data_Structure
graphs	I-Data_Structure
that	O
are	O
generated	O
solely	O
at	B-Library
runtime	I-Library
(	O
as	O
happens	O
in	O
ray	B-Algorithm
tracing	I-Algorithm
rendering	B-Algorithm
programs	O
)	O
,	O
require	O
defining	O
of	O
group	O
nodes	O
in	O
a	O
more	O
automated	O
fashion	O
.	O
</s>
<s>
A	O
raytracer	B-Algorithm
,	O
for	O
example	O
,	O
will	O
take	O
a	O
scene	O
description	O
of	O
a	O
3D	O
model	O
and	O
build	O
an	O
internal	O
representation	O
that	O
breaks	O
up	O
its	O
individual	O
parts	O
into	O
bounding	B-Algorithm
boxes	I-Algorithm
(	O
also	O
called	O
bounding	O
slabs	O
)	O
.	O
</s>
<s>
If	O
the	O
user	O
has	O
magnified	O
a	O
document	O
so	O
that	O
only	O
part	O
of	O
it	O
is	O
visible	O
on	O
his	O
computer	O
screen	O
,	O
and	O
then	O
scrolls	O
in	O
it	O
,	O
it	O
is	O
useful	O
to	O
use	O
a	O
bounding	B-Algorithm
box	I-Algorithm
(	O
or	O
in	O
this	O
case	O
,	O
a	O
bounding	O
rectangle	O
scheme	O
)	O
to	O
quickly	O
determine	O
which	O
scene	B-Data_Structure
graph	I-Data_Structure
elements	O
are	O
visible	O
and	O
thus	O
actually	O
need	O
to	O
be	O
drawn	O
.	O
</s>
<s>
Depending	O
on	O
the	O
particulars	O
of	O
the	O
application	O
's	O
drawing	O
performance	O
,	O
a	O
large	O
part	O
of	O
the	O
scene	B-Data_Structure
graph	I-Data_Structure
's	O
design	O
can	O
be	O
impacted	O
by	O
rendering	B-Algorithm
efficiency	O
considerations	O
.	O
</s>
<s>
In	O
3D	O
video	O
games	O
such	O
as	O
Quake	B-Application
,	O
binary	O
space	B-Algorithm
partitioning	I-Algorithm
(	O
BSP	O
)	O
trees	O
are	O
heavily	O
favored	O
to	O
minimize	O
visibility	O
tests	O
.	O
</s>
<s>
BSP	O
trees	O
,	O
however	O
,	O
take	O
a	O
very	O
long	O
time	O
to	O
compute	O
from	O
design	O
scene	B-Data_Structure
graphs	I-Data_Structure
,	O
and	O
must	O
be	O
recomputed	O
if	O
the	O
design	O
scene	B-Data_Structure
graph	I-Data_Structure
changes	O
,	O
so	O
the	O
levels	O
tend	O
to	O
remain	O
static	O
,	O
and	O
dynamic	O
characters	O
are	O
n't	O
generally	O
considered	O
in	O
the	O
spatial	B-Algorithm
partitioning	I-Algorithm
scheme	O
.	O
</s>
<s>
Scene	B-Data_Structure
graphs	I-Data_Structure
for	O
dense	O
regular	O
objects	O
such	O
as	O
heightfields	B-Data_Structure
and	O
polygon	O
meshes	O
tend	O
to	O
employ	O
quadtrees	B-Data_Structure
and	O
octrees	B-Data_Structure
,	O
which	O
are	O
specialized	O
variants	O
of	O
a	O
3D	O
bounding	B-Algorithm
box	I-Algorithm
hierarchy	O
.	O
</s>
<s>
Since	O
a	O
heightfield	B-Data_Structure
occupies	O
a	O
box	O
volume	O
itself	O
,	O
recursively	O
subdividing	O
this	O
box	O
into	O
eight	O
subboxes	O
(	O
hence	O
the	O
'	O
oct	O
 '	O
in	O
octree	B-Data_Structure
)	O
until	O
individual	O
heightfield	B-Data_Structure
elements	O
are	O
reached	O
is	O
efficient	O
and	O
natural	O
.	O
</s>
<s>
A	O
quadtree	B-Data_Structure
is	O
simply	O
a	O
2D	O
octree	B-Data_Structure
.	O
</s>
<s>
PHIGS	B-Library
was	O
the	O
first	O
commercial	O
scene	B-Data_Structure
graph	I-Data_Structure
specification	O
,	O
and	O
became	O
an	O
ANSI	O
standard	O
in	O
1988	O
.	O
</s>
<s>
Disparate	O
implementations	O
were	O
provided	O
by	O
Unix	B-Application
hardware	O
vendors	O
.	O
</s>
<s>
The	O
HOOPS	B-Language
3D	I-Language
Graphics	I-Language
System	I-Language
appears	O
to	O
have	O
been	O
the	O
first	O
commercial	O
scene	B-Data_Structure
graph	I-Data_Structure
library	O
provided	O
by	O
a	O
single	O
software	O
vendor	O
.	O
</s>
<s>
Silicon	O
Graphics	O
(	O
SGI	O
)	O
released	O
OpenGL	B-Library
Performer	I-Library
or	O
more	O
commonly	O
called	O
Performer	B-Library
in	O
1991	O
which	O
was	O
the	O
primary	O
scenegraph	B-Data_Structure
system	O
for	O
most	O
SGI	O
products	O
into	O
the	O
future	O
.	O
</s>
<s>
IRIS	B-Application
Inventor	I-Application
1.0	O
(	O
1992	O
)	O
was	O
released	O
by	O
SGI	O
,	O
which	O
was	O
a	O
high	O
level	O
scene	B-Data_Structure
graph	I-Data_Structure
built	O
on	O
top	O
of	O
Performer	B-Library
.	O
</s>
<s>
It	O
was	O
followed	O
up	O
with	O
Open	B-Application
Inventor	I-Application
in	O
1994	O
,	O
another	O
iteration	O
of	O
the	O
high	O
level	O
scene	B-Data_Structure
graph	I-Data_Structure
built	O
on	O
top	O
of	O
newer	O
releases	O
of	O
Performer	B-Library
.	O
</s>
<s>
More	O
3D	O
scene	B-Data_Structure
graph	I-Data_Structure
libraries	O
can	O
be	O
found	O
in	O
:Category:3D	O
scenegraph	B-Data_Structure
APIs	B-General_Concept
.	O
</s>
<s>
X3D	B-Application
is	O
a	O
royalty-free	O
open	O
standards	O
file	O
format	O
and	O
run-time	O
architecture	O
to	O
represent	O
and	O
communicate	O
3D	O
scenes	O
and	O
objects	O
using	O
XML	B-Protocol
.	O
</s>
<s>
It	O
is	O
an	O
ISO-ratified	O
standard	O
that	O
provides	O
a	O
system	O
for	O
the	O
storage	O
,	O
retrieval	O
and	O
playback	O
of	O
real-time	O
graphics	O
content	O
embedded	O
in	O
applications	O
,	O
all	O
within	O
an	O
open	B-Architecture
architecture	I-Architecture
to	O
support	O
a	O
wide	O
array	B-Data_Structure
of	O
domains	O
and	O
user	O
scenarios	O
.	O
</s>
