<s>
Vector	B-Application
General	I-Application
(	O
VG	O
)	O
was	O
a	O
series	O
of	O
graphics	O
terminals	O
and	O
the	O
name	O
of	O
the	O
Californian	O
company	O
that	O
produced	O
them	O
.	O
</s>
<s>
The	O
terminals	O
were	O
based	O
on	O
a	O
common	O
platform	O
that	O
read	O
vectors	O
provided	O
by	O
a	O
host	O
minicomputer	B-Architecture
and	O
included	O
hardware	O
that	O
could	O
perform	O
basic	O
mathematical	O
transformations	O
in	O
the	O
terminal	O
.	O
</s>
<s>
The	O
transformed	O
vectors	O
were	O
then	O
displayed	O
on	O
the	O
terminal	O
's	O
built-in	O
vector	B-General_Concept
monitor	I-General_Concept
.	O
</s>
<s>
In	O
contrast	O
to	O
similar	O
terminals	O
from	O
other	O
vendors	O
,	O
the	O
Vector	B-Application
General	I-Application
systems	O
included	O
little	O
internal	O
memory	B-General_Concept
.	O
</s>
<s>
Instead	O
,	O
they	O
stored	O
vectors	O
on	O
the	O
host	O
computer	O
's	O
memory	B-General_Concept
and	O
accessed	O
them	O
via	O
direct	B-General_Concept
memory	I-General_Concept
access	I-General_Concept
(	O
DMA	O
)	O
.	O
</s>
<s>
Fully	O
equipped	O
VG3D	O
terminals	O
ran	O
at	O
about	O
$	O
31,000	O
including	O
a	O
low-end	O
PDP-11	B-Device
computer	O
,	O
compared	O
to	O
machines	O
like	O
the	O
IBM	B-Device
2250	I-Device
which	O
cost	O
$	O
100,000	O
for	O
just	O
the	O
terminal	O
.	O
</s>
<s>
Among	O
a	O
number	O
of	O
famous	O
uses	O
known	O
within	O
the	O
computer	O
graphics	O
field	O
,	O
it	O
was	O
a	O
VG3D	O
terminal	O
connected	O
to	O
a	O
PDP-11/45	B-Device
that	O
was	O
used	O
to	O
produce	O
the	O
"	O
attacking	O
the	O
Death	B-Operating_System
Star	I-Operating_System
will	O
not	O
be	O
easy	O
"	O
animations	O
in	O
Star	O
Wars	O
.	O
</s>
<s>
A	O
common	O
attempt	O
in	O
the	O
late	O
1960s	O
to	O
improve	O
performance	O
of	O
graphics	O
display	O
,	O
especially	O
in	O
3D	O
,	O
was	O
to	O
use	O
special	O
terminals	O
that	O
held	O
a	O
list	O
of	O
vectors	O
in	O
internal	O
memory	B-General_Concept
and	O
then	O
used	O
hardware	O
or	O
software	O
running	O
in	O
the	O
display	O
controller	O
to	O
provide	O
basic	O
transformations	O
like	O
rotation	O
and	O
scaling	O
.	O
</s>
<s>
Systems	O
performing	O
at	O
least	O
some	O
of	O
these	O
operations	O
included	O
the	O
IDI	O
,	O
Adage	O
,	O
and	O
Imlac	B-Device
PDS-1	I-Device
.	O
</s>
<s>
A	O
key	O
innovation	O
in	O
the	O
VG	O
series	O
terminals	O
was	O
the	O
use	O
of	O
direct	B-General_Concept
memory	I-General_Concept
access	I-General_Concept
(	O
DMA	O
)	O
to	O
allow	O
it	O
to	O
access	O
a	O
host	O
computer	O
's	O
memory	B-General_Concept
.	O
</s>
<s>
This	O
meant	O
that	O
the	O
terminals	O
did	O
not	O
need	O
much	O
storage	O
of	O
their	O
own	O
,	O
and	O
gave	O
them	O
the	O
ability	O
to	O
rapidly	O
access	O
the	O
data	O
without	O
it	O
being	O
copied	O
over	O
a	O
slower	O
link	O
like	O
the	O
serial-based	O
Tektronix	B-General_Concept
4010	I-General_Concept
or	O
similar	O
systems	O
.	O
</s>
<s>
The	O
basic	O
concept	O
was	O
that	O
the	O
host	O
computer	O
would	O
run	O
calculations	O
to	O
produce	O
a	O
series	O
of	O
points	O
for	O
the	O
2D	O
or	O
3D	O
model	O
and	O
express	O
that	O
as	O
12-bit	O
values	O
,	O
normally	O
stored	O
in	O
16-bit	O
words	O
with	O
extra	O
stuffed	B-Protocol
status	O
bits	O
.	O
</s>
<s>
Each	O
point	O
was	O
read	O
one-by-one	O
into	O
the	O
local	O
memory	B-General_Concept
registers	I-General_Concept
for	O
temporary	O
storage	O
while	O
mathematical	O
functions	O
were	O
applied	O
to	O
them	O
to	O
scale	O
,	O
translate	O
and	O
(	O
optionally	O
)	O
rotate	O
,	O
and	O
when	O
the	O
final	O
values	O
were	O
calculated	O
,	O
those	O
points	O
were	O
sent	O
to	O
the	O
cathode-ray	B-Device
tube	I-Device
(	O
CRT	O
)	O
for	O
display	O
.	O
</s>
<s>
The	O
most	O
basic	O
system	O
included	O
the	O
hardware	O
needed	O
to	O
pan	O
and	O
zoom	O
2D	O
images	O
,	O
in	O
which	O
case	O
the	O
terminal	O
containing	O
it	O
would	O
be	O
known	O
as	O
a	O
Vector	B-Application
General	I-Application
2D	O
.	O
</s>
<s>
The	O
company	O
referred	O
to	O
this	O
type	O
of	O
operation	O
as	O
"	O
random	B-General_Concept
scan	I-General_Concept
"	O
,	O
although	O
it	O
is	O
universally	O
referred	O
to	O
as	O
a	O
vector	B-General_Concept
monitor	I-General_Concept
in	O
modern	O
references	O
.	O
</s>
<s>
The	O
most	O
common	O
was	O
a	O
70-key	O
keyboard	B-Device
,	O
while	O
others	O
included	O
a	O
bank	O
of	O
momentary	O
pushbuttons	O
switches	O
with	O
internal	O
register-controlled	O
lights	O
,	O
a	O
graphics	B-Device
tablet	I-Device
,	O
a	O
light	B-Device
pen	I-Device
,	O
a	O
dial	B-Device
box	I-Device
,	O
and	O
a	O
joystick	B-Device
.	O
</s>
<s>
The	O
system	O
allowed	O
vectors	O
to	O
be	O
represented	O
in	O
a	O
number	O
of	O
ways	O
in	O
memory	B-General_Concept
.	O
</s>
<s>
This	O
could	O
halve	O
the	O
number	O
of	O
points	O
needed	O
to	O
describe	O
a	O
complete	O
drawing	O
,	O
if	O
the	O
data	O
was	O
continuous	O
like	O
a	O
line	B-Application
chart	I-Application
.	O
</s>
<s>
"	O
Incremental	O
"	O
vectors	O
further	O
reduced	O
memory	B-General_Concept
by	O
using	O
only	O
6-bits	O
for	O
each	O
point	O
,	O
allowing	O
the	O
data	O
to	O
be	O
packed	B-Application
into	O
less	O
memory	B-General_Concept
in	O
the	O
host	O
.	O
</s>
<s>
Finally	O
,	O
"	O
autoincrementing	O
"	O
vectors	O
further	O
reduced	O
the	O
memory	B-General_Concept
requirements	O
by	O
requiring	O
only	O
one	O
value	O
to	O
be	O
stored	O
,	O
with	O
the	O
others	O
being	O
incremented	O
by	O
a	O
preset	O
amount	O
as	O
each	O
new	O
point	O
was	O
read	O
in	O
.	O
</s>
<s>
The	O
system	O
included	O
a	O
number	O
of	O
greek	O
letters	O
and	O
mathematical	O
symbols	O
in	O
addition	O
to	O
the	O
normal	O
ASCII	B-Protocol
characters	I-Protocol
.	O
</s>
<s>
The	O
terminal	O
periodically	O
read	O
the	O
main	O
memory	B-General_Concept
of	O
the	O
host	O
computer	O
using	O
DMA	O
to	O
refresh	O
the	O
display	O
.	O
</s>
<s>
This	O
allowed	O
the	O
display	O
to	O
perform	O
a	O
sort	O
of	O
"	O
page	O
flipping	O
"	O
by	O
writing	O
out	O
separate	O
sets	O
of	O
points	O
within	O
the	O
computer	O
's	O
memory	B-General_Concept
and	O
then	O
changing	O
the	O
display	O
all	O
at	O
once	O
by	O
changing	O
the	O
value	O
of	O
register	O
14	O
to	O
point	O
to	O
a	O
different	O
base	O
address	O
.	O
</s>
<s>
This	O
was	O
limited	O
by	O
the	O
amount	O
of	O
memory	B-General_Concept
available	O
on	O
the	O
host	O
computer	O
.	O
</s>
<s>
The	O
VG3D	O
is	O
historically	O
notable	O
for	O
its	O
use	O
in	O
Star	O
Wars	O
,	O
but	O
is	O
also	O
well	O
known	O
for	O
its	O
early	O
role	O
in	O
the	O
development	O
of	O
computer	B-Application
aided	I-Application
design	I-Application
.	O
</s>
<s>
Larry	O
Cuba	O
produced	O
two	O
segments	O
of	O
computer	O
animation	O
for	O
Star	O
Wars	O
on	O
a	O
PDP-11/45	B-Device
with	O
a	O
VG3D	O
terminal	O
.	O
</s>
<s>
The	O
first	O
segment	O
,	O
which	O
shows	O
the	O
exterior	O
of	O
the	O
Death	B-Operating_System
Star	I-Operating_System
,	O
is	O
based	O
entirely	O
on	O
the	O
VG3D	O
's	O
internal	O
display	O
capabilities	O
.	O
</s>
<s>
The	O
model	O
consisted	O
of	O
a	O
simple	O
series	O
of	O
3D	O
points	O
representing	O
the	O
outline	O
of	O
the	O
station	O
held	O
in	O
the	O
PDP-11	B-Device
'	O
s	O
memory	B-General_Concept
,	O
constructed	O
algorithmically	O
using	O
the	O
associated	O
GRASS	B-Language
programming	I-Language
language	I-Language
's	O
curve	O
generation	O
code	O
.	O
</s>
<s>
Mike	O
Muuss	O
recounts	O
that	O
the	O
US	O
Army	O
's	O
Ballistic	O
Research	O
Laboratory	O
had	O
purchased	O
a	O
Cyber	B-Device
173	I-Device
and	O
three	O
workstations	O
consisting	O
of	O
a	O
VG3D	O
terminal	O
and	O
a	O
PDP-11/34	O
to	O
drive	O
it	O
.	O
</s>
<s>
He	O
first	O
output	O
it	O
as	O
a	O
static	O
image	O
on	O
a	O
Tektronix	B-General_Concept
4014	I-General_Concept
,	O
but	O
the	O
next	O
night	O
managed	O
to	O
get	O
the	O
display	O
onto	O
the	O
VG3D	O
where	O
it	O
could	O
be	O
easily	O
spun	O
around	O
using	O
the	O
internal	O
vector	O
hardware	O
.	O
</s>
<s>
The	O
demo	O
became	O
so	O
well	O
known	O
that	O
Muuss	O
was	O
able	O
to	O
begin	O
development	O
of	O
BRL-CAD	B-Language
.	O
</s>
