<s>
Computer-aided	B-Application
design	I-Application
(	O
CAD	B-Application
)	O
is	O
the	O
use	O
of	O
computers	O
(	O
or	O
)	O
to	O
aid	O
in	O
the	O
creation	O
,	O
modification	O
,	O
analysis	O
,	O
or	O
optimization	O
of	O
a	O
design	O
.	O
</s>
<s>
Designs	O
made	O
through	O
CAD	B-Application
software	I-Application
are	O
helpful	O
in	O
protecting	O
products	O
and	O
inventions	O
when	O
used	O
in	O
patent	O
applications	O
.	O
</s>
<s>
CAD	B-Application
output	O
is	O
often	O
in	O
the	O
form	O
of	O
electronic	O
files	O
for	O
print	O
,	O
machining	O
,	O
or	O
other	O
manufacturing	O
operations	O
.	O
</s>
<s>
The	O
terms	O
computer-aided	B-Application
drafting	I-Application
(	O
CAD	B-Application
)	O
and	O
computer	B-Application
aided	I-Application
design	I-Application
and	I-Application
drafting	I-Application
(	O
CADD	B-Application
)	O
are	O
also	O
used	O
.	O
</s>
<s>
In	O
mechanical	O
design	O
it	O
is	O
known	O
as	O
mechanical	O
design	O
automation	O
(	O
MDA	O
)	O
,	O
which	O
includes	O
the	O
process	O
of	O
creating	O
a	O
technical	B-Application
drawing	I-Application
with	O
the	O
use	O
of	O
computer	B-Application
software	I-Application
.	O
</s>
<s>
CAD	B-Application
software	I-Application
for	O
mechanical	O
design	O
uses	O
either	O
vector-based	O
graphics	O
to	O
depict	O
the	O
objects	O
of	O
traditional	O
drafting	O
,	O
or	O
may	O
also	O
produce	O
raster	B-Algorithm
graphics	I-Algorithm
showing	O
the	O
overall	O
appearance	O
of	O
designed	O
objects	O
.	O
</s>
<s>
As	O
in	O
the	O
manual	O
drafting	O
of	O
technical	B-Application
and	O
engineering	B-Architecture
drawings	I-Architecture
,	O
the	O
output	O
of	O
CAD	B-Application
must	O
convey	O
information	O
,	O
such	O
as	O
materials	O
,	O
processes	O
,	O
dimensions	O
,	O
and	O
tolerances	O
,	O
according	O
to	O
application-specific	O
conventions	O
.	O
</s>
<s>
CAD	B-Application
may	O
be	O
used	O
to	O
design	O
curves	O
and	O
figures	O
in	O
two-dimensional	O
(	O
2D	O
)	O
space	O
;	O
or	O
curves	O
,	O
surfaces	O
,	O
and	O
solids	O
in	O
three-dimensional	O
(	O
3D	O
)	O
space	O
.	O
</s>
<s>
CAD	B-Application
is	O
an	O
important	O
industrial	O
art	O
extensively	O
used	O
in	O
many	O
applications	O
,	O
including	O
automotive	O
,	O
shipbuilding	O
,	O
and	O
aerospace	O
industries	O
,	O
industrial	O
and	O
architectural	O
design	O
(	O
building	B-Architecture
information	I-Architecture
modeling	I-Architecture
)	O
,	O
prosthetics	O
,	O
and	O
many	O
more	O
.	O
</s>
<s>
CAD	B-Application
is	O
also	O
widely	O
used	O
to	O
produce	O
computer	O
animation	O
for	O
special	O
effects	O
in	O
movies	O
,	O
advertising	O
and	O
technical	B-Application
manuals	O
,	O
often	O
called	O
DCC	O
digital	O
content	O
creation	O
.	O
</s>
<s>
Because	O
of	O
its	O
enormous	O
economic	O
importance	O
,	O
CAD	B-Application
has	O
been	O
a	O
major	O
driving	O
force	O
for	O
research	O
in	O
computational	O
geometry	O
,	O
computer	O
graphics	O
(	O
both	O
hardware	O
and	O
software	O
)	O
,	O
and	O
discrete	O
differential	O
geometry	O
.	O
</s>
<s>
The	O
design	O
of	O
geometric	B-Application
models	I-Application
for	O
object	O
shapes	O
,	O
in	O
particular	O
,	O
is	O
occasionally	O
called	O
computer-aided	B-Application
geometric	I-Application
design	I-Application
(	O
CAGD	B-Application
)	O
.	O
</s>
<s>
Computer-aided	B-Application
design	I-Application
is	O
one	O
of	O
the	O
many	O
tools	O
used	O
by	O
engineers	O
and	O
designers	O
and	O
is	O
used	O
in	O
many	O
ways	O
depending	O
on	O
the	O
profession	O
of	O
the	O
user	O
and	O
the	O
type	O
of	O
software	O
in	O
question	O
.	O
</s>
<s>
CAD	B-Application
is	O
one	O
part	O
of	O
the	O
whole	O
digital	O
product	O
development	O
(	O
DPD	O
)	O
activity	O
within	O
the	O
product	O
lifecycle	O
management	O
(	O
PLM	O
)	O
processes	O
,	O
and	O
as	O
such	O
is	O
used	O
together	O
with	O
other	O
tools	O
,	O
which	O
are	O
either	O
integrated	O
modules	O
or	O
stand-alone	O
products	O
,	O
such	O
as	O
:	O
</s>
<s>
Photorealistic	B-Application
rendering	I-Application
and	O
motion	O
simulation	O
.	O
</s>
<s>
CAD	B-Application
is	O
also	O
used	O
for	O
the	O
accurate	O
creation	O
of	O
photo	O
simulations	O
that	O
are	O
often	O
required	O
in	O
the	O
preparation	O
of	O
environmental	O
impact	O
reports	O
,	O
in	O
which	O
computer-aided	B-Application
designs	I-Application
of	O
intended	O
buildings	O
are	O
superimposed	O
into	O
photographs	O
of	O
existing	O
environments	O
to	O
represent	O
what	O
that	O
locale	O
will	O
be	O
like	O
,	O
where	O
the	O
proposed	O
facilities	O
are	O
allowed	O
to	O
be	O
built	O
.	O
</s>
<s>
Potential	O
blockage	O
of	O
view	O
corridors	O
and	O
shadow	O
studies	O
are	O
also	O
frequently	O
analyzed	O
through	O
the	O
use	O
of	O
CAD	B-Application
.	O
</s>
<s>
The	O
features	O
in	O
the	O
CAD	B-Application
system	O
can	O
be	O
used	O
for	O
the	O
variety	O
of	O
tools	O
for	O
measurement	O
such	O
as	O
tensile	O
strength	O
,	O
yield	O
strength	O
,	O
electrical	O
,	O
or	O
electromagnetic	O
properties	O
.	O
</s>
<s>
There	O
are	O
several	O
different	O
types	O
of	O
CAD	B-Application
,	O
each	O
requiring	O
the	O
operator	O
to	O
think	O
differently	O
about	O
how	O
to	O
use	O
them	O
and	O
design	O
their	O
virtual	O
components	O
in	O
a	O
different	O
manner	O
for	O
each	O
.	O
</s>
<s>
3D	O
wireframe	B-Algorithm
is	O
basically	O
an	O
extension	O
of	O
2D	O
drafting	O
(	O
not	O
often	O
used	O
today	O
)	O
into	O
a	O
three-dimensional	O
space	O
.	O
</s>
<s>
The	O
operator	O
approaches	O
these	O
in	O
a	O
similar	O
fashion	O
to	O
the	O
2D	O
systems	O
,	O
although	O
many	O
3D	O
systems	O
allow	O
using	O
the	O
wireframe	B-Algorithm
model	I-Algorithm
to	O
make	O
the	O
final	O
engineering	B-Architecture
drawing	I-Architecture
views	O
.	O
</s>
<s>
Originally	O
software	O
for	O
CAD	B-Application
systems	O
was	O
developed	O
with	O
computer	O
languages	O
such	O
as	O
Fortran	B-Application
,	O
ALGOL	B-Language
but	O
with	O
the	O
advancement	O
of	O
object-oriented	B-Language
programming	I-Language
methods	O
this	O
has	O
radically	O
changed	O
.	O
</s>
<s>
Typical	O
modern	O
parametric	O
feature-based	O
modeler	O
and	O
freeform	O
surface	O
systems	O
are	O
built	O
around	O
a	O
number	O
of	O
key	O
C	B-Language
modules	O
with	O
their	O
own	O
APIs	B-Application
.	O
</s>
<s>
A	O
CAD	B-Application
system	O
can	O
be	O
seen	O
as	O
built	O
up	O
from	O
the	O
interaction	O
of	O
a	O
graphical	B-Application
user	I-Application
interface	I-Application
(	O
GUI	B-Application
)	O
with	O
NURBS	B-Algorithm
geometry	O
or	O
boundary	B-Algorithm
representation	I-Algorithm
(	O
B-rep	B-Algorithm
)	O
data	O
via	O
a	O
geometric	B-Algorithm
modeling	I-Algorithm
kernel	I-Algorithm
.	O
</s>
<s>
A	O
geometry	B-Application
constraint	I-Application
engine	I-Application
may	O
also	O
be	O
employed	O
to	O
manage	O
the	O
associative	O
relationships	O
between	O
geometry	O
,	O
such	O
as	O
wireframe	B-Algorithm
geometry	O
in	O
a	O
sketch	O
or	O
components	O
in	O
an	O
assembly	O
.	O
</s>
<s>
That	O
said	O
,	O
CAD	B-Application
models	I-Application
can	O
be	O
generated	O
by	O
a	O
computer	O
after	O
the	O
physical	O
prototype	O
has	O
been	O
scanned	O
using	O
an	O
industrial	O
CT	O
scanning	O
machine	O
.	O
</s>
<s>
Today	O
,	O
CAD	B-Application
systems	O
exist	O
for	O
all	O
the	O
major	O
platforms	O
(	O
Windows	B-Application
,	O
Linux	B-Application
,	O
UNIX	B-Application
and	O
Mac	B-Operating_System
OS	I-Operating_System
X	I-Operating_System
)	O
;	O
some	O
packages	O
support	O
multiple	O
platforms	O
.	O
</s>
<s>
Currently	O
,	O
no	O
special	O
hardware	O
is	O
required	O
for	O
most	O
CAD	B-Application
software	I-Application
.	O
</s>
<s>
However	O
,	O
some	O
CAD	B-Application
systems	O
can	O
do	O
graphically	O
and	O
computationally	O
intensive	O
tasks	O
,	O
so	O
a	O
modern	O
graphics	B-Device
card	I-Device
,	O
high	O
speed	O
(	O
and	O
possibly	O
multiple	O
)	O
CPUs	O
and	O
large	O
amounts	O
of	O
RAM	B-Architecture
may	O
be	O
recommended	O
.	O
</s>
<s>
The	O
human-machine	O
interface	O
is	O
generally	O
via	O
a	O
computer	B-Device
mouse	I-Device
but	O
can	O
also	O
be	O
via	O
a	O
pen	O
and	O
digitizing	O
graphics	B-Device
tablet	I-Device
.	O
</s>
<s>
Some	O
systems	O
also	O
support	O
stereoscopic	O
glasses	O
for	O
viewing	B-Application
the	I-Application
3D	I-Application
model	I-Application
.	O
</s>
<s>
Starting	O
around	O
the	O
mid-1960s	O
,	O
with	O
the	O
IBM	O
Drafting	O
System	O
,	O
computer-aided	B-Application
design	I-Application
systems	O
began	O
to	O
provide	O
more	O
capability	O
than	O
just	O
an	O
ability	O
to	O
reproduce	O
manual	O
drafting	O
with	O
electronic	O
drafting	O
,	O
the	O
cost-benefit	O
for	O
companies	O
to	O
switch	O
to	O
CAD	B-Application
became	O
apparent	O
.	O
</s>
<s>
The	O
benefits	O
of	O
CAD	B-Application
systems	O
over	O
manual	O
drafting	O
are	O
the	O
capabilities	O
one	O
often	O
takes	O
for	O
granted	O
from	O
computer	O
systems	O
today	O
;	O
automated	O
generation	O
of	O
bills	O
of	O
materials	O
,	O
auto	O
layout	O
in	O
integrated	O
circuits	O
,	O
interference	O
checking	O
,	O
and	O
many	O
others	O
.	O
</s>
<s>
Eventually	O
,	O
CAD	B-Application
provided	O
the	O
designer	O
with	O
the	O
ability	O
to	O
perform	O
engineering	O
calculations	O
.	O
</s>
<s>
CAD	B-Application
was	O
a	O
revolutionary	O
change	O
in	O
the	O
engineering	O
industry	O
,	O
where	O
draftsmen	O
,	O
designers	O
,	O
and	O
engineering	O
roles	O
begin	O
to	O
merge	O
.	O
</s>
<s>
CAD	B-Application
is	O
an	O
example	O
of	O
the	O
pervasive	O
effect	O
computers	O
were	O
beginning	O
to	O
have	O
on	O
the	O
industry	O
.	O
</s>
<s>
Current	O
computer-aided	B-Application
design	I-Application
software	O
packages	O
range	O
from	O
2D	O
vector-based	O
drafting	O
systems	O
to	O
3D	O
solid	O
and	O
surface	O
modelers	O
.	O
</s>
<s>
Modern	O
CAD	B-Application
packages	O
can	O
also	O
frequently	O
allow	O
rotations	O
in	O
three	O
dimensions	O
,	O
allowing	O
viewing	O
of	O
a	O
designed	O
object	O
from	O
any	O
desired	O
angle	O
,	O
even	O
from	O
the	O
inside	O
looking	O
out	O
.	O
</s>
<s>
Some	O
CAD	B-Application
software	I-Application
is	O
capable	O
of	O
dynamic	O
mathematical	O
modeling	O
.	O
</s>
<s>
CAD	B-Application
technology	B-Algorithm
is	O
used	O
in	O
the	O
design	O
of	O
tools	O
and	O
machinery	O
and	O
in	O
the	O
drafting	O
and	O
design	O
of	O
all	O
types	O
of	O
buildings	O
,	O
from	O
small	O
residential	O
types	O
(	O
houses	O
)	O
to	O
the	O
largest	O
commercial	O
and	O
industrial	O
structures	O
(	O
hospitals	O
and	O
factories	O
)	O
.	O
</s>
<s>
CAD	B-Application
is	O
mainly	O
used	O
for	O
detailed	O
engineering	O
of	O
3D	O
models	O
or	O
2D	O
drawings	O
of	O
physical	O
components	O
,	O
but	O
it	O
is	O
also	O
used	O
throughout	O
the	O
engineering	O
process	O
from	O
conceptual	O
design	O
and	O
layout	O
of	O
products	O
,	O
through	O
strength	O
and	O
dynamic	O
analysis	O
of	O
assemblies	O
to	O
definition	O
of	O
manufacturing	O
methods	O
of	O
components	O
.	O
</s>
<s>
Furthermore	O
,	O
many	O
CAD	B-Application
applications	O
now	O
offer	O
advanced	O
rendering	O
and	O
animation	O
capabilities	O
so	O
engineers	O
can	O
better	O
visualize	O
their	O
product	O
designs	O
.	O
</s>
<s>
4D	O
BIM	B-Architecture
is	O
a	O
type	O
of	O
virtual	O
construction	O
engineering	O
simulation	O
incorporating	O
time	O
or	O
schedule-related	O
information	O
for	O
project	O
management	O
.	O
</s>
<s>
CAD	B-Application
has	O
become	O
an	O
especially	O
important	O
technology	B-Algorithm
within	O
the	O
scope	O
of	O
computer-aided	O
technologies	O
,	O
with	O
benefits	O
such	O
as	O
lower	O
product	O
development	O
costs	O
and	O
a	O
greatly	O
shortened	O
design	O
cycle	O
.	O
</s>
<s>
CAD	B-Application
enables	O
designers	O
to	O
layout	O
and	O
develop	O
work	O
on	O
screen	O
,	O
print	O
it	O
out	O
and	O
save	O
it	O
for	O
future	O
editing	O
,	O
saving	O
time	O
on	O
their	O
drawings	O
.	O
</s>
<s>
In	O
the	O
beginning	O
of	O
2000	O
,	O
some	O
CAD	B-Application
system	O
software	O
vendors	O
might	O
have	O
shipped	O
their	O
distributions	O
with	O
a	O
dedicated	O
license	O
manager	O
software	O
that	O
might	O
control	O
how	O
often	O
or	O
how	O
many	O
users	O
can	O
utilize	O
CAD	B-Application
system	O
.	O
</s>
<s>
It	O
could	O
run	O
either	O
on	O
a	O
local	O
machine	O
(	O
by	O
loading	O
from	O
a	O
local	O
storage	O
device	O
)	O
or	O
a	O
local	O
network	B-Application
fileserver	I-Application
and	O
was	O
usually	O
tied	O
to	O
a	O
specific	O
IP	O
address	O
in	O
latter	O
case	O
.	O
</s>
<s>
CAD	B-Application
software	I-Application
enables	O
engineers	O
and	O
architects	O
to	O
design	O
,	O
inspect	O
and	O
manage	O
engineering	O
projects	O
within	O
an	O
integrated	O
graphical	B-Application
user	I-Application
interface	I-Application
(	O
GUI	B-Application
)	O
on	O
a	O
personal	B-Device
computer	I-Device
system	O
.	O
</s>
<s>
Most	O
applications	O
support	O
solid	O
modeling	O
with	O
boundary	B-Algorithm
representation	I-Algorithm
(	O
B-Rep	B-Algorithm
)	O
and	O
NURBS	B-Algorithm
geometry	O
,	O
and	O
enable	O
the	O
same	O
to	O
be	O
published	O
in	O
a	O
variety	O
of	O
formats	O
.	O
</s>
<s>
A	O
geometric	B-Algorithm
modeling	I-Algorithm
kernel	I-Algorithm
is	O
a	O
software	O
component	O
that	O
provides	O
solid	O
modeling	O
and	O
surface	O
modeling	O
features	O
to	O
CAD	B-Application
applications	O
.	O
</s>
<s>
Based	O
on	O
market	O
statistics	O
,	O
commercial	B-Application
software	I-Application
from	O
Autodesk	O
,	O
Dassault	O
Systems	O
,	O
Siemens	O
PLM	O
Software	O
,	O
and	O
PTC	O
dominate	O
the	O
CAD	B-Application
industry	O
.	O
</s>
<s>
The	O
following	O
is	O
a	O
list	O
of	O
major	O
CAD	B-Application
applications	O
,	O
grouped	O
by	O
usage	O
statistics	O
.	O
</s>
