<s>
Newell	B-Algorithm
's	I-Algorithm
Algorithm	I-Algorithm
is	O
a	O
3D	O
computer	O
graphics	O
procedure	O
for	O
elimination	O
of	O
polygon	B-General_Concept
cycles	O
in	O
the	O
depth	O
sorting	O
required	O
in	O
hidden	O
surface	O
removal	O
.	O
</s>
<s>
In	O
the	O
depth	O
sorting	O
phase	O
of	O
hidden	O
surface	O
removal	O
,	O
if	O
two	O
polygons	B-General_Concept
have	O
no	O
overlapping	O
extents	O
or	O
extreme	O
minimum	O
and	O
maximum	O
values	O
in	O
the	O
x	O
,	O
y	O
,	O
and	O
z	O
directions	O
,	O
then	O
they	O
can	O
be	O
easily	O
sorted	O
.	O
</s>
<s>
If	O
two	O
polygons	B-General_Concept
,	O
and	O
,	O
do	O
have	O
overlapping	O
extents	O
in	O
the	O
Z	O
direction	O
,	O
then	O
it	O
is	O
possible	O
that	O
cutting	O
is	O
necessary	O
.	O
</s>
<s>
In	O
that	O
case	O
Newell	B-Algorithm
's	I-Algorithm
algorithm	I-Algorithm
tests	O
the	O
following	O
:	O
</s>
<s>
The	O
polygons	B-General_Concept
must	O
be	O
planar	O
.	O
</s>
<s>
If	O
there	O
is	O
an	O
attempt	O
to	O
switch	O
the	O
order	O
of	O
a	O
polygon	B-General_Concept
a	O
second	O
time	O
,	O
there	O
is	O
a	O
visibility	O
cycle	O
,	O
and	O
the	O
polygons	B-General_Concept
must	O
be	O
split	O
.	O
</s>
<s>
Splitting	O
is	O
accomplished	O
by	O
selecting	O
one	O
polygon	B-General_Concept
and	O
cutting	O
it	O
along	O
the	O
line	O
of	O
intersection	O
with	O
the	O
other	O
polygon	B-General_Concept
.	O
</s>
<s>
The	O
above	O
tests	O
are	O
again	O
performed	O
,	O
and	O
the	O
algorithm	O
continues	O
until	O
all	O
polygons	B-General_Concept
pass	O
the	O
above	O
tests	O
.	O
</s>
