<s>
OpenGL	B-Library
Performer	I-Library
,	O
formerly	O
known	O
as	O
IRIS	B-Library
Performer	I-Library
and	O
commonly	O
referred	O
to	O
simply	O
as	O
Performer	B-Library
,	O
is	O
a	O
commercial	O
library	O
of	O
utility	O
code	O
built	O
on	O
top	O
of	O
OpenGL	B-Application
for	O
the	O
purpose	O
of	O
enabling	O
hard	B-General_Concept
real-time	I-General_Concept
visual	O
simulation	O
applications	O
.	O
</s>
<s>
OpenGL	B-Library
Performer	I-Library
was	O
developed	O
by	O
SGI	O
which	O
continues	O
to	O
maintain	O
and	O
enhance	O
it	O
.	O
</s>
<s>
OpenGL	B-Library
Performer	I-Library
is	O
available	O
for	O
IRIX	B-Operating_System
,	O
Linux	B-Application
,	O
and	O
several	O
versions	O
of	O
Microsoft	B-Application
Windows	I-Application
.	O
</s>
<s>
Both	O
ANSI	O
C	O
and	O
C++	B-Language
bindings	O
are	O
available	O
.	O
</s>
<s>
Performer	B-Library
came	O
about	O
in	O
1991	O
when	O
a	O
group	O
from	O
SGI	O
's	O
Open	B-Application
Inventor	I-Application
project	O
,	O
then	O
known	O
as	O
IRIS	B-Application
Inventor	I-Application
,	O
decided	O
to	O
focus	O
on	O
performance	O
rather	O
than	O
ease	O
of	O
programmability	O
.	O
</s>
<s>
Whereas	O
Inventor	O
delivered	O
easy-to-use	O
objects	O
and	O
various	O
UI	O
elements	O
to	O
interact	O
with	O
them	O
,	O
Performer	B-Library
focused	O
on	O
a	O
scene	B-Data_Structure
graph	I-Data_Structure
system	O
that	O
could	O
be	O
re-arranged	O
on	O
the	O
fly	O
for	O
performance	O
reasons	O
,	O
allowing	O
the	O
various	O
passes	O
of	O
a	O
rendering	O
task	O
to	O
be	O
performed	O
in	O
parallel	O
in	O
multiple	O
threads	B-Operating_System
.	O
</s>
<s>
Performer	B-Library
allowed	O
the	O
scene	O
to	O
describe	O
levels	O
of	O
detail	O
with	O
hysteresis	O
bands	O
and	O
fade	O
capabilities	O
.	O
</s>
<s>
Other	O
key	O
features	O
of	O
Performer	B-Library
were	O
the	O
use	O
of	O
symmetric	B-Operating_System
multi-processing	I-Operating_System
capabilities	O
,	O
support	O
multiple	O
graphics	O
pipes	O
and	O
the	O
ability	O
to	O
utilize	O
the	O
scalable	O
resources	O
of	O
high	O
end	O
systems	O
.	O
</s>
<s>
In	O
this	O
regard	O
Performer	B-Library
was	O
actually	O
simple	O
to	O
use	O
given	O
the	O
underlying	O
complexity	O
.	O
</s>
<s>
Application	O
culling	O
and	O
rendering	O
could	O
be	O
running	O
in	O
different	O
threads	B-Operating_System
locked	O
to	O
different	O
physical	O
processors	O
.	O
</s>
<s>
In	O
a	O
multi-pipe	O
(	O
multiple	O
graphics	O
subsystems	O
)	O
configuration	O
rendering	O
to	O
each	O
graphics	O
pipe	O
would	O
have	O
a	O
dedicated	O
thread	B-Operating_System
and	O
similarly	O
culling	O
would	O
also	O
have	O
a	O
dedicated	O
processor	O
.	O
</s>
<s>
Advanced	O
features	O
like	O
database	O
paging	O
,	O
texture	O
paging	O
and	O
point	O
light	O
source	O
management	O
(	O
for	O
flight	O
simulation	O
)	O
and	O
intersection	O
testing	O
for	O
collision	O
detection	O
would	O
also	O
have	O
dedicated	O
processors	O
allowing	O
asynchronous	B-Architecture
I/O	I-Architecture
and	O
processing	O
to	O
occur	O
without	O
negatively	O
impacting	O
graphics	O
performance	O
.	O
</s>
<s>
Most	O
of	O
this	O
complexity	O
was	O
hidden	O
beneath	O
a	O
simpler	O
scene	B-Data_Structure
graph	I-Data_Structure
API	O
with	O
relatively	O
high	O
level	O
configuration	O
calls	O
which	O
could	O
be	O
made	O
to	O
set	O
up	O
the	O
threads	B-Operating_System
and	O
inter-process	O
communication	O
.	O
</s>
<s>
Performer	B-Library
did	O
not	O
have	O
a	O
native	O
file	O
format	O
,	O
merely	O
plugin	O
loaders	O
from	O
3rd	O
parties	O
such	O
as	O
MultiGen	O
's	O
OpenFlight	B-Application
format	O
loader	O
.	O
</s>
<s>
By	O
the	O
mid-1990s	O
it	O
started	O
to	O
become	O
clear	O
that	O
there	O
was	O
no	O
reason	O
that	O
Inventor	O
and	O
Performer	B-Library
could	O
not	O
be	O
combined	O
.	O
</s>
<s>
This	O
led	O
to	O
the	O
Cosmo	O
3D	O
project	O
that	O
SGI	O
was	O
intending	O
to	O
build	O
both	O
Inventor	O
and	O
Performer	B-Library
(	O
now	O
essentially	O
API	B-General_Concept
shims	I-General_Concept
)	O
out	O
of	O
,	O
as	O
well	O
as	O
promote	O
as	O
a	O
new	O
and	O
higher-level	O
standardized	O
API	O
for	O
future	O
work	O
on	O
the	O
SGI	O
platform	O
.	O
</s>
<s>
However	O
,	O
after	O
the	O
first	O
beta	O
release	O
of	O
Cosmo	O
3D	O
,	O
SGi	O
joined	O
with	O
Intel	O
and	O
IBM	O
(	O
and	O
later	O
DEC	O
)	O
to	O
create	O
OpenGL++	B-Library
,	O
essentially	O
a	O
cleaned	O
up	O
version	O
of	O
Cosmo	O
.	O
</s>
<s>
This	O
project	O
died	O
when	O
SGI	O
turned	O
their	O
attention	O
to	O
an	O
almost	O
identical	O
project	O
with	O
Microsoft	O
known	O
as	O
Fahrenheit	B-Library
,	O
which	O
was	O
also	O
killed	O
.	O
</s>
<s>
Today	O
Inventor	O
and	O
Performer	B-Library
remain	O
separate	O
products	O
,	O
and	O
none	O
of	O
the	O
combined	O
versions	O
ever	O
saw	O
the	O
light	O
of	O
day	O
.	O
</s>
<s>
Performer	B-Library
consists	O
primarily	O
of	O
two	O
libraries	O
:	O
the	O
lower-level	O
libpr	O
and	O
the	O
higher-level	O
libpf	O
.	O
</s>
<s>
The	O
libpf	O
library	O
includes	O
functions	O
for	O
the	O
generation	O
and	O
manipulation	O
of	O
hierarchical	O
scene	B-Data_Structure
graphs	I-Data_Structure
,	O
scene	O
processing	O
(	O
simulation	O
,	O
intersection	O
,	O
culling	O
,	O
and	O
drawing	O
tasks	O
)	O
,	O
level-of-detail	O
management	O
,	O
asynchronous	O
database	O
paging	O
,	O
dynamic	O
coordinate	O
systems	O
,	O
environment	O
models	O
,	O
light	O
points	O
,	O
and	O
so	O
on	O
.	O
</s>
<s>
Other	O
Performer	B-Library
libraries--libpfutil	O
,	O
libpfdb	O
,	O
libpfui	O
,	O
etc.--provide	O
functions	O
for	O
generating	O
optimized	O
geometry	O
,	O
database	O
conversion	O
,	O
device	O
input	O
(	O
such	O
as	O
for	O
interfacing	O
with	O
external	O
flyboxes	O
and	O
MIL-STD-1553	O
mux	O
busses	O
)	O
,	O
motion	O
models	O
,	O
collision	O
models	O
,	O
and	O
a	O
format-independent	O
database	O
interface	O
that	O
supports	O
common	O
data	O
formats	O
such	O
as	O
Open	B-Application
Inventor	I-Application
,	O
OpenFlight	B-Application
,	O
Designer	O
's	O
Workbench	O
,	O
Medit	O
,	O
and	O
Wavefront	O
.	O
</s>
