<s>
In	O
vector	O
computer	O
graphics	O
,	O
CAD	B-Application
systems	I-Application
,	O
and	O
geographic	B-Application
information	I-Application
systems	I-Application
,	O
geometric	B-Algorithm
primitive	I-Algorithm
(	O
or	O
prim	O
)	O
is	O
the	O
simplest	O
(	O
i.e.	O
</s>
<s>
Sometimes	O
the	O
subroutines	O
that	O
draw	O
the	O
corresponding	O
objects	O
are	O
called	O
"	O
geometric	B-Algorithm
primitives	I-Algorithm
"	O
as	O
well	O
.	O
</s>
<s>
The	O
most	O
"	O
primitive	B-Algorithm
"	O
primitives	B-Algorithm
are	O
point	O
and	O
straight	O
line	O
segment	O
,	O
which	O
were	O
all	O
that	O
early	O
vector	O
graphics	O
systems	O
had	O
.	O
</s>
<s>
In	O
constructive	O
solid	O
geometry	O
,	O
primitives	B-Algorithm
are	O
simple	O
geometric	O
shapes	O
such	O
as	O
a	O
cube	O
,	O
cylinder	O
,	O
sphere	O
,	O
cone	O
,	O
pyramid	O
,	O
torus	O
.	O
</s>
<s>
Modern	O
2D	O
computer	O
graphics	O
systems	O
may	O
operate	O
with	O
primitives	B-Algorithm
which	O
are	O
curves	O
(	O
segments	O
of	O
straight	O
lines	O
,	O
circles	O
and	O
more	O
complicated	O
curves	O
)	O
,	O
as	O
well	O
as	O
shapes	O
(	O
boxes	O
,	O
arbitrary	O
polygons	B-General_Concept
,	O
circles	O
)	O
.	O
</s>
<s>
A	O
common	O
set	O
of	O
two-dimensional	O
primitives	B-Algorithm
includes	O
lines	O
,	O
points	O
,	O
and	O
polygons	B-General_Concept
,	O
although	O
some	O
people	O
prefer	O
to	O
consider	O
triangles	O
primitives	B-Algorithm
,	O
because	O
every	O
polygon	B-General_Concept
can	O
be	O
constructed	O
from	O
triangles	O
.	O
</s>
<s>
All	O
other	O
graphic	O
elements	O
are	O
built	O
up	O
from	O
these	O
primitives	B-Algorithm
.	O
</s>
<s>
In	O
three	O
dimensions	O
,	O
triangles	O
or	O
polygons	B-General_Concept
positioned	O
in	O
three-dimensional	O
space	O
can	O
be	O
used	O
as	O
primitives	B-Algorithm
to	O
model	O
more	O
complex	O
3D	O
forms	O
.	O
</s>
<s>
may	O
be	O
considered	O
primitives	B-Algorithm
;	O
in	O
other	O
cases	O
,	O
curves	O
are	O
complex	O
forms	O
created	O
from	O
many	O
straight	O
,	O
primitive	B-Algorithm
shapes	O
.	O
</s>
<s>
The	O
set	O
of	O
geometric	B-Algorithm
primitives	I-Algorithm
is	O
based	O
on	O
the	O
dimension	O
of	O
the	O
region	O
being	O
represented	O
:	O
</s>
<s>
In	O
GIS	B-Application
,	O
the	O
terrain	O
surface	O
is	O
often	O
spoken	O
of	O
colloquially	O
as	O
"	O
2	O
1/2	O
dimensional	O
,	O
"	O
because	O
only	O
the	O
upper	O
surface	O
needs	O
to	O
be	O
represented	O
.	O
</s>
<s>
Thus	O
,	O
vector	O
data	O
structures	O
typically	O
represent	O
geometric	B-Algorithm
primitives	I-Algorithm
using	O
a	O
strategic	O
sample	O
,	O
organized	O
in	O
structures	O
that	O
facilitate	O
the	O
software	O
interpolating	B-Algorithm
the	O
remainder	O
of	O
the	O
shape	O
at	O
the	O
time	O
of	O
analysis	O
or	O
display	O
,	O
using	O
the	O
algorithms	O
of	O
Computational	O
geometry	O
.	O
</s>
<s>
The	O
software	O
is	O
expected	O
to	O
interpolate	B-Algorithm
the	O
intervening	O
shape	O
of	O
the	O
line	O
between	O
adjacent	O
points	O
in	O
the	O
list	O
as	O
a	O
parametric	O
curve	O
,	O
most	O
commonly	O
a	O
straight	O
line	O
,	O
but	O
other	O
types	O
of	O
curves	O
are	O
frequently	O
available	O
,	O
including	O
circular	O
arcs	O
,	O
cubic	B-Algorithm
splines	I-Algorithm
,	O
and	O
Bézier	O
curves	O
.	O
</s>
<s>
A	O
Polygon	B-General_Concept
is	O
a	O
polyline	O
that	O
closes	O
at	O
its	O
endpoints	O
,	O
representing	O
the	O
boundary	O
of	O
a	O
two-dimensional	O
region	O
.	O
</s>
<s>
A	O
Parametric	O
shape	O
is	O
a	O
standardized	O
two-dimensional	O
or	O
three-dimensional	O
shape	O
defined	O
by	O
a	O
minimal	O
set	O
of	O
parameters	O
,	O
such	O
as	O
an	O
ellipse	O
defined	O
by	O
two	O
points	O
at	O
its	O
foci	O
,	O
or	O
three	O
points	O
at	O
its	O
center	O
,	O
vertex	B-Algorithm
,	O
and	O
co-vertex	O
.	O
</s>
<s>
A	O
Polyhedron	O
or	O
Polygon	B-Algorithm
mesh	I-Algorithm
is	O
a	O
set	O
of	O
polygon	B-General_Concept
faces	O
in	O
three-dimensional	O
space	O
that	O
are	O
connected	O
at	O
their	O
edges	O
to	O
completely	O
enclose	O
a	O
volumetric	O
region	O
.	O
</s>
<s>
A	O
triangle	B-Algorithm
mesh	I-Algorithm
is	O
a	O
subtype	O
of	O
polyhedron	O
in	O
which	O
all	O
faces	O
must	O
be	O
triangles	O
,	O
the	O
only	O
polygon	B-General_Concept
that	O
will	O
always	O
be	O
planar	O
,	O
including	O
the	O
Triangulated	B-Algorithm
irregular	I-Algorithm
network	I-Algorithm
(	O
TIN	O
)	O
commonly	O
used	O
in	O
GIS	B-Application
.	O
</s>
<s>
A	O
parametric	O
mesh	B-Algorithm
represents	O
a	O
three-dimensional	O
surface	O
by	O
a	O
connected	O
set	O
of	O
parametric	O
functions	O
,	O
similar	O
to	O
a	O
spline	O
or	O
Bézier	O
curve	O
in	O
two	O
dimensions	O
.	O
</s>
<s>
The	O
most	O
common	O
structure	O
is	O
the	O
Non-uniform	B-Algorithm
rational	I-Algorithm
B-spline	I-Algorithm
(	O
NURBS	B-Algorithm
)	O
,	O
supported	O
by	O
most	O
CAD	B-Application
and	O
animation	O
software	O
.	O
</s>
<s>
A	O
wide	O
variety	O
of	O
vector	O
data	O
structures	O
and	O
formats	O
have	O
been	O
developed	O
during	O
the	O
history	O
of	O
Geographic	B-Application
information	I-Application
systems	I-Application
,	O
but	O
they	O
share	O
a	O
fundamental	O
basis	O
of	O
storing	O
a	O
core	O
set	O
of	O
geometric	B-Algorithm
primitives	I-Algorithm
to	O
represent	O
the	O
location	O
and	O
extent	O
of	O
geographic	O
phenomena	O
.	O
</s>
<s>
They	O
also	O
share	O
the	O
need	O
to	O
store	O
a	O
set	O
of	O
attributes	O
of	O
each	O
geographic	O
feature	O
alongside	O
its	O
shape	O
;	O
traditionally	O
,	O
this	O
has	O
been	O
accomplished	O
using	O
the	O
data	O
models	O
,	O
data	O
formats	O
,	O
and	O
even	O
software	O
of	O
relational	B-Application
databases	I-Application
.	O
</s>
<s>
Early	O
vector	O
formats	O
,	O
such	O
as	O
POLYVRT	O
,	O
the	O
ARC/INFO	O
Coverage	O
,	O
and	O
the	O
Esri	O
shapefile	O
support	O
a	O
basic	O
set	O
of	O
geometric	B-Algorithm
primitives	I-Algorithm
:	O
points	O
,	O
polylines	O
,	O
and	O
polygons	B-General_Concept
,	O
only	O
in	O
two	O
dimensional	O
space	O
and	O
the	O
latter	O
two	O
with	O
only	O
straight	O
line	O
interpolation	B-Algorithm
.	O
</s>
<s>
TIN	O
data	O
structures	O
for	O
representing	O
terrain	O
surfaces	O
as	O
triangle	B-Algorithm
meshes	I-Algorithm
were	O
also	O
added	O
.	O
</s>
<s>
Since	O
the	O
mid	O
1990s	O
,	O
new	O
formats	O
have	O
been	O
developed	O
that	O
extend	O
the	O
range	O
of	O
available	O
primitives	B-Algorithm
,	O
generally	O
standardized	O
by	O
the	O
Open	O
Geospatial	O
Consortium	O
's	O
Simple	O
Features	O
specification	O
.	O
</s>
<s>
Common	O
geometric	B-Algorithm
primitive	I-Algorithm
extensions	O
include	O
:	O
three-dimensional	O
coordinates	O
for	O
points	O
,	O
lines	O
,	O
and	O
polygons	B-General_Concept
;	O
a	O
fourth	O
"	O
dimension	O
"	O
to	O
represent	O
a	O
measured	O
attribute	O
or	O
time	O
;	O
curved	O
segments	O
in	O
lines	O
and	O
polygons	B-General_Concept
;	O
text	O
annotation	O
as	O
a	O
form	O
of	O
geometry	O
;	O
and	O
polygon	B-Algorithm
meshes	I-Algorithm
for	O
three-dimensional	O
objects	O
.	O
</s>
<s>
In	O
CAD	B-Application
software	I-Application
or	O
3D	O
modelling	O
,	O
the	O
interface	O
may	O
present	O
the	O
user	O
with	O
the	O
ability	O
to	O
create	O
primitives	B-Algorithm
which	O
may	O
be	O
further	O
modified	O
by	O
edits	O
.	O
</s>
<s>
In	O
this	O
use	O
the	O
primitive	B-Algorithm
is	O
just	O
a	O
convenient	O
starting	O
point	O
,	O
rather	O
than	O
the	O
fundamental	O
unit	O
of	O
modelling	O
.	O
</s>
<s>
A	O
3D	O
package	O
may	O
also	O
include	O
a	O
list	O
of	O
extended	O
primitives	B-Algorithm
which	O
are	O
more	O
complex	O
shapes	O
that	O
come	O
with	O
the	O
package	O
.	O
</s>
<s>
For	O
example	O
,	O
a	O
teapot	O
is	O
listed	O
as	O
a	O
primitive	B-Algorithm
in	O
3D	B-Language
Studio	I-Language
Max	I-Language
.	O
</s>
<s>
Various	O
graphics	B-Architecture
accelerators	I-Architecture
exist	O
with	O
hardware	B-General_Concept
acceleration	I-General_Concept
for	O
rendering	O
specific	O
primitives	B-Algorithm
such	O
as	O
lines	O
or	O
triangles	O
,	O
frequently	O
with	O
texture	O
mapping	O
and	O
shaders	O
.	O
</s>
<s>
Modern	O
3D	B-Architecture
accelerators	I-Architecture
typically	O
accept	O
sequences	O
of	O
triangles	O
as	O
triangle	O
strips	O
.	O
</s>
