<s>
PHIGS	B-Library
(	O
Programmer	B-Library
's	I-Library
Hierarchical	I-Library
Interactive	I-Library
Graphics	I-Library
System	I-Library
)	O
is	O
an	O
application	B-Application
programming	I-Application
interface	I-Application
(	O
API	B-Application
)	O
standard	O
for	O
rendering	O
3D	O
computer	O
graphics	O
,	O
considered	O
to	O
be	O
the	O
3D	O
graphics	O
standard	O
for	O
the	O
1980s	O
through	O
the	O
early	O
1990s	O
.	O
</s>
<s>
Subsequently	O
,	O
a	O
combination	O
of	O
features	O
and	O
power	O
led	O
to	O
the	O
rise	O
of	O
OpenGL	B-Application
,	O
which	O
became	O
the	O
most	O
popular	O
professional	O
3D	O
API	B-Application
of	O
the	O
mid	O
to	O
late	O
1990s	O
.	O
</s>
<s>
Large	O
vendors	O
typically	O
offered	O
versions	O
of	O
PHIGS	B-Library
for	O
their	O
platforms	O
,	O
including	O
DEC	B-Library
PHIGS	I-Library
,	O
IBM	O
's	O
graPHIGS	B-Library
and	O
Sun	O
's	O
SunPHIGS	B-Library
.	O
</s>
<s>
It	O
could	O
also	O
be	O
used	O
within	O
the	O
X	B-Operating_System
Window	I-Operating_System
System	I-Operating_System
,	O
supported	O
via	O
PEX	O
.	O
</s>
<s>
PEX	O
consisted	O
of	O
an	O
extension	O
to	O
X	B-Operating_System
,	O
adding	O
commands	O
that	O
would	O
be	O
forwarded	O
from	O
the	O
X	B-Operating_System
server	O
to	O
the	O
PEX	O
system	O
for	O
rendering	O
.	O
</s>
<s>
PHIGS	B-Library
was	O
designed	O
in	O
the	O
1980s	O
,	O
inheriting	O
many	O
of	O
its	O
ideas	O
from	O
the	O
Graphical	O
Kernel	O
System	O
(	O
GKS	O
)	O
of	O
the	O
late	O
1970s	O
,	O
and	O
became	O
a	O
standard	O
by	O
1988	O
:	O
ANSI	O
(	O
ANSI	O
X3.144-1988	O
)	O
,	O
FIPS	O
(	O
FIPS	B-Library
153	I-Library
)	O
and	O
then	O
ISO	O
(	O
ISO/IEC	B-Library
9592	I-Library
and	O
ISO/IEC	B-Library
9593	I-Library
)	O
.	O
</s>
<s>
Due	O
to	O
its	O
early	O
gestation	O
,	O
the	O
standard	O
supports	O
only	O
the	O
most	O
basic	O
3D	O
graphics	O
,	O
including	O
basic	O
geometry	O
and	O
meshes	O
,	O
and	O
only	O
the	O
basic	O
Gouraud	B-Algorithm
,	O
"	O
Dot	O
"	O
,	O
and	O
Phong	O
shading	O
for	O
rendering	O
scenes	O
.	O
</s>
<s>
Although	O
PHIGS	B-Library
ultimately	O
expanded	O
to	O
contain	O
advanced	O
functions	O
(	O
including	O
the	O
more	O
accurate	O
Phong	O
lighting	O
model	O
and	O
Data	O
Mapping	O
)	O
,	O
other	O
features	O
considered	O
standard	O
by	O
the	O
mid-1990s	O
were	O
not	O
supported	O
(	O
notably	O
texture	O
mapping	O
)	O
,	O
nor	O
were	O
many	O
machines	O
of	O
the	O
era	O
physically	O
capable	O
of	O
optimizing	O
it	O
to	O
perform	O
in	O
real	O
time	O
.	O
</s>
<s>
The	O
word	O
"	O
hierarchical	O
"	O
in	O
the	O
name	O
refers	O
to	O
a	O
notable	O
feature	O
of	O
PHIGS	B-Library
:	O
unlike	O
most	O
graphics	O
systems	O
,	O
PHIGS	B-Library
included	O
a	O
scene	B-Data_Structure
graph	I-Data_Structure
system	O
as	O
a	O
part	O
of	O
the	O
basic	O
standard	O
.	O
</s>
<s>
CSSes	O
could	O
be	O
shared	O
among	O
a	O
number	O
of	O
virtual	O
devices	O
,	O
known	O
under	O
PHIGS	B-Library
as	O
workstations	O
,	O
each	O
of	O
which	O
could	O
contain	O
any	O
number	O
of	O
views	O
.	O
</s>
<s>
Displaying	O
graphics	O
on	O
the	O
screen	O
in	O
PHIGS	B-Library
was	O
a	O
three-step	O
process	O
;	O
first	O
the	O
model	O
would	O
be	O
built	O
into	O
a	O
CSS	O
,	O
then	O
a	O
workstation	O
would	O
be	O
created	O
and	O
opened	O
,	O
and	O
finally	O
the	O
model	O
would	O
be	O
connected	O
to	O
the	O
workstation	O
.	O
</s>
<s>
PHIGS	B-Library
originally	O
lacked	O
the	O
capability	O
to	O
render	O
illuminated	O
scenes	O
,	O
and	O
was	O
superseded	O
by	O
PHIGS+	B-Library
.	O
</s>
<s>
PHIGS+	B-Library
works	O
in	O
essentially	O
the	O
same	O
manner	O
,	O
but	O
added	O
methods	O
for	O
lighting	O
and	O
filling	O
surfaces	O
within	O
a	O
3D	O
scene	O
.	O
</s>
<s>
PHIGS+	B-Library
also	O
introduced	O
more	O
advanced	O
graphics	O
primitives	O
,	O
such	O
as	O
Non-uniform	B-Algorithm
rational	I-Algorithm
B-spline	I-Algorithm
(	O
NURBS	B-Algorithm
)	O
surfaces	O
.	O
</s>
<s>
An	O
ad	O
hoc	O
ANSI	O
committee	O
was	O
formed	O
around	O
these	O
proposed	O
extensions	O
to	O
PHIGS	B-Library
,	O
changing	O
its	O
name	O
to	O
the	O
more	O
descriptive	O
and	O
(	O
optimistically	O
)	O
extensible	O
name	O
"	O
PHIGS	B-Library
PLUS	O
"	O
--	O
"	O
PLUS	O
"	O
being	O
a	O
slightly	O
tongue-in-cheek	O
acronym	O
for	O
"	O
Plus	O
Lumière	O
Und	O
Surfaces	O
"	O
(	O
the	O
two	O
major	O
areas	O
of	O
advancement	O
over	O
the	O
base	O
PHIGS	B-Library
standard	O
)	O
.	O
</s>
<s>
OpenGL	B-Application
,	O
unlike	O
PHIGS	B-Library
,	O
was	O
an	O
immediate-mode	O
rendering	O
system	O
with	O
no	O
"	O
state	O
"	O
;	O
once	O
an	O
object	O
is	O
sent	O
to	O
a	O
view	O
to	O
be	O
rendered	O
it	O
essentially	O
disappears	O
.	O
</s>
<s>
For	O
simple	O
projects	O
,	O
PHIGS	B-Library
was	O
considerably	O
easier	O
to	O
use	O
and	O
work	O
with	O
.	O
</s>
<s>
However	O
,	O
OpenGL	B-Application
's	O
"	O
low-level	O
"	O
API	B-Application
allowed	O
the	O
programmer	O
to	O
make	O
dramatic	O
improvements	O
in	O
rendering	O
performance	O
by	O
first	O
examining	O
the	O
data	O
on	O
the	O
CPU-side	O
before	O
trying	O
to	O
send	O
it	O
over	O
the	O
bus	O
to	O
the	O
graphics	O
engine	O
.	O
</s>
<s>
This	O
was	O
kept	O
private	O
in	O
PHIGS	B-Library
,	O
making	O
it	O
much	O
more	O
difficult	O
to	O
tune	O
performance	O
,	O
but	O
enabling	O
tuning	O
to	O
happen	O
"	O
for	O
free	O
"	O
within	O
the	O
PHIGS	B-Library
implementation	O
.	O
</s>
<s>
Given	O
the	O
low	O
performance	O
systems	O
of	O
the	O
era	O
and	O
the	O
need	O
for	O
high-performance	O
rendering	O
,	O
OpenGL	B-Application
was	O
generally	O
considered	O
to	O
be	O
much	O
more	O
"	O
powerful	O
"	O
for	O
3D	O
programming	O
.	O
</s>
<s>
PHIGS	B-Library
fell	O
into	O
disuse	O
.	O
</s>
<s>
PEX	O
was	O
mostly	O
removed	O
from	O
XFree86	B-Device
4.2.x	O
(	O
2002	O
)	O
and	O
finally	O
removed	O
from	O
the	O
X	B-Operating_System
Window	I-Operating_System
System	I-Operating_System
altogether	O
in	O
X11R6.7.0	O
(	O
April	O
2004	O
)	O
.	O
</s>
