<s>
Visualization	B-Language
Library	I-Language
(	O
VL	O
)	O
is	O
an	O
open	O
source	O
C++	B-Language
middleware	O
for	O
2D/3D	O
graphics	O
applications	O
based	O
on	O
OpenGL	B-Application
4	O
,	O
designed	O
to	O
develop	O
portable	O
applications	O
for	O
the	O
Microsoft	B-Application
Windows	I-Application
,	O
Linux	B-Application
and	O
Mac	B-Operating_System
OS	I-Operating_System
X	I-Operating_System
operating	O
systems	O
.	O
</s>
<s>
Visualization	B-Language
Library	I-Language
was	O
designed	O
to	O
:	O
</s>
<s>
Implement	O
an	O
intuitive	O
,	O
thin	O
and	O
portable	O
C++	B-Language
wrapper	O
around	O
OpenGL	B-Application
4	O
.	O
</s>
<s>
Be	O
fully	O
compatible	O
with	O
older	O
versions	O
of	O
OpenGL	B-Application
(	O
1.x	O
,	O
2.x	O
and	O
3.x	O
)	O
.	O
</s>
<s>
Avoid	O
the	O
architectural	O
limitations	O
of	O
the	O
uber-scene-graph	O
paradigm	O
.	O
</s>
<s>
Visualization	B-Language
Library	I-Language
design	O
is	O
based	O
on	O
algorithmic	O
and	O
data	O
structure	O
specialization	O
and	O
separation	O
,	O
unlike	O
many	O
other	O
3D	O
frameworks	O
part	O
of	O
the	O
so-called	O
"	O
uber	O
scene	B-Data_Structure
graph	I-Data_Structure
"	O
family	O
,	O
that	O
is	O
,	O
those	O
3d	O
engines	O
that	O
keep	O
all	O
the	O
rendering	O
information	O
in	O
a	O
single	O
hierarchical	O
structure	O
.	O
</s>
<s>
Thus	O
,	O
Visualization	B-Language
Library	I-Language
uses	O
different	O
data	O
structures	O
(	O
possibly	O
hierarchical	O
)	O
to	O
manage	O
each	O
particular	O
domain	O
of	O
the	O
rendering	O
pipeline	O
.	O
</s>
<s>
For	O
example	O
,	O
the	O
transform	O
tree	O
is	O
kept	O
in	O
a	O
separate	O
tree	O
graph	O
data	O
structure	O
and	O
the	O
objects	O
part	O
of	O
the	O
scene	O
(	O
"	O
Actors	O
"	O
in	O
Visualization	B-Language
Library	I-Language
parlance	O
)	O
can	O
freely	O
refer	O
to	O
a	O
node	O
of	O
the	O
transform	O
tree	O
.	O
</s>
<s>
Actors	O
are	O
kept	O
in	O
their	O
own	O
scene	O
partitioning	O
data	O
structure	O
from	O
which	O
their	O
visibility	O
is	O
tested	O
against	O
the	O
view	B-General_Concept
frustum	I-General_Concept
and	O
from	O
which	O
eventually	O
they	O
are	O
extracted	O
at	O
rendering	O
time	O
to	O
be	O
part	O
of	O
the	O
rendering	O
queue	O
.	O
</s>
<s>
This	O
allow	O
VL	O
to	O
be	O
independent	O
from	O
,	O
and	O
take	O
advantage	O
of	O
,	O
virtually	O
any	O
type	O
of	O
scene	O
management	O
technique	O
,	O
such	O
as	O
PVS	O
,	O
portal/sector	O
,	O
KdTree	B-Data_Structure
,	O
quadtrees	B-Data_Structure
,	O
octrees	B-Data_Structure
etc	O
.	O
</s>
<s>
However	O
VL	O
provides	O
a	O
ShaderNode	O
class	O
,	O
as	O
a	O
high	O
level	O
service	O
,	O
that	O
allows	O
the	O
user	O
to	O
update	O
and	O
manage	O
Shaders	O
in	O
a	O
hierarchical	O
way	O
using	O
inheritance	O
rules	O
similar	O
to	O
the	O
ones	O
commonly	O
available	O
in	O
uber-scene-graph	O
based	O
frameworks	O
.	O
</s>
<s>
OpenGL	B-Application
Support	O
:	O
1.x	O
,	O
2.x	O
,	O
3.x	O
,	O
4.x	O
.	O
</s>
<s>
OpenGL	B-Language
Shading	I-Language
Language	I-Language
1.x	O
to	O
4.x	O
support	O
including	O
geometry	O
and	O
tessellation	O
shaders	O
.	O
</s>
<s>
Provided	O
scene	O
managers	O
:	O
generic	O
hierarchical	O
volume	O
tree	O
,	O
KdTree	B-Data_Structure
,	O
portal-based	O
scene	B-Data_Structure
graph	I-Data_Structure
.	O
</s>
<s>
GLSL	B-Language
based	O
C++	B-Language
advanced	O
vector/matrix	O
library	O
.	O
</s>
<s>
The	O
first	O
public	O
release	O
of	O
Visualization	B-Language
Library	I-Language
was	O
on	O
May	O
7	O
,	O
2007	O
.	O
</s>
<s>
Visualization	B-Language
Library	I-Language
is	O
currently	O
at	O
its	O
second	O
stable	O
release	O
,	O
VL	O
2011.05.1140	O
,	O
which	O
follows	O
the	O
first	O
one	O
,	O
VL	O
2009.07.640	O
.	O
</s>
<s>
While	O
the	O
design	O
remained	O
essentially	O
the	O
same	O
the	O
latest	O
stable	O
release	O
differs	O
from	O
its	O
predecessor	O
mainly	O
for	O
:	O
supporting	O
OpenGL	B-Application
3	O
and	O
4	O
and	O
in	O
particular	O
tessellation	O
shaders	O
,	O
double	O
precision	O
uniform	O
variables	O
,	O
new	O
texture	O
formats	O
such	O
as	O
multisample	O
textures	O
and	O
texture	O
objects	O
,	O
extensive	O
framebuffer	O
object	O
support	O
and	O
a	O
better	O
tuning	O
for	O
applications	O
that	O
make	O
heavy	O
use	O
of	O
GLSL	B-Language
,	O
among	O
many	O
other	O
enhancements	O
.	O
</s>
