<s>
An	O
edge	B-General_Concept
loop	I-General_Concept
,	O
in	O
computer	O
graphics	O
,	O
can	O
loosely	O
be	O
defined	O
as	O
a	O
set	O
of	O
connected	O
edges	O
across	O
a	O
surface	O
.	O
</s>
<s>
In	O
a	O
stricter	O
sense	O
,	O
an	O
edge	B-General_Concept
loop	I-General_Concept
is	O
defined	O
as	O
a	O
set	O
of	O
edges	O
where	O
the	O
loop	O
follows	O
the	O
middle	O
edge	O
in	O
every	O
'	O
four	O
way	O
junction	O
 '	O
.	O
</s>
<s>
If	O
you	O
follow	O
the	O
middle	O
'	O
road	O
 '	O
each	O
time	O
,	O
you	O
would	O
either	O
end	O
up	O
with	O
a	O
completed	O
loop	O
or	O
the	O
edge	B-General_Concept
loop	I-General_Concept
would	O
end	O
at	O
another	O
type	O
of	O
junction	O
.	O
</s>
<s>
Edge	B-General_Concept
loops	I-General_Concept
are	O
especially	O
practical	O
in	O
organic	O
models	O
which	O
need	O
to	O
be	O
animated	O
.	O
</s>
<s>
In	O
organic	O
modeling	O
,	O
edge	B-General_Concept
loops	I-General_Concept
play	O
a	O
vital	O
role	O
in	O
proper	O
deformation	O
of	O
the	O
mesh	O
.	O
</s>
<s>
A	O
properly	O
modeled	O
mesh	O
will	O
take	O
into	O
careful	O
consideration	O
the	O
placement	O
and	O
termination	O
of	O
these	O
edge	B-General_Concept
loops	I-General_Concept
.	O
</s>
<s>
Generally	O
,	O
edge	B-General_Concept
loops	I-General_Concept
follow	O
the	O
structure	O
and	O
contour	O
of	O
the	O
muscles	O
that	O
they	O
mimic	O
.	O
</s>
<s>
For	O
example	O
,	O
in	O
modeling	O
a	O
human	O
face	O
,	O
edge	B-General_Concept
loops	I-General_Concept
should	O
follow	O
the	O
orbicularis	O
oculi	O
muscle	O
around	O
the	O
eyes	O
and	O
the	O
orbicularis	O
oris	O
muscle	O
around	O
the	O
mouth	O
.	O
</s>
<s>
An	O
edge	B-General_Concept
loop	I-General_Concept
closely	O
mimics	O
how	O
real	O
muscles	O
work	O
,	O
and	O
if	O
built	O
correctly	O
,	O
provides	O
control	O
over	O
contour	O
and	O
silhouette	O
in	O
any	O
position	O
.	O
</s>
<s>
"	O
Edge	B-General_Concept
loop	I-General_Concept
"	O
was	O
first	O
coined	O
as	O
a	O
modelling	O
term	O
in	O
1999	O
by	O
3D	O
artist	O
Bay	O
Raitt	O
,	O
in	O
an	O
article	O
called	O
Digital	O
sculpting	O
techniques	O
for	O
3D	O
Design	O
magazine	O
.	O
</s>
