<s>
Fast	B-Algorithm
approximate	I-Algorithm
anti-aliasing	I-Algorithm
(	O
FXAA	B-Algorithm
)	O
is	O
a	O
screen-space	O
anti-aliasing	B-Algorithm
algorithm	O
created	O
by	O
Timothy	O
Lottes	O
at	O
Nvidia	O
.	O
</s>
<s>
FXAA	B-Algorithm
3	O
is	O
released	O
under	O
a	O
public	O
domain	O
license	O
.	O
</s>
<s>
A	O
later	O
version	O
,	O
FXAA	B-Algorithm
3.11	O
,	O
is	O
released	O
under	O
a	O
3-clause	O
BSD	O
license	O
.	O
</s>
<s>
This	O
data	O
could	O
be	O
passed	O
into	O
the	O
FXAA	B-Algorithm
algorithm	O
from	O
the	O
rendering	O
step	O
as	O
an	O
alpha	B-Algorithm
channel	I-Algorithm
embedded	O
into	O
the	O
image	O
to	O
be	O
antialiased	O
,	O
calculated	O
from	O
the	O
rendered	O
image	O
,	O
or	O
approximated	O
by	O
using	O
the	O
green	O
channel	O
as	O
the	O
luminance	O
data	O
.	O
</s>
<s>
Find	O
high	O
contrast	O
pixels	B-Algorithm
by	O
using	O
a	O
high	O
pass	O
filter	O
that	O
uses	O
the	O
luminance	O
data	O
.	O
</s>
<s>
Low	O
contrast	O
pixels	B-Algorithm
that	O
are	O
found	O
are	O
excluded	O
from	O
being	O
further	O
altered	O
by	O
FXAA	B-Algorithm
.	O
</s>
<s>
The	O
high	O
pass	O
filter	O
that	O
excludes	O
low	O
contrast	O
pixels	B-Algorithm
can	O
be	O
tuned	O
to	O
balance	O
speed	O
and	O
sensitivity	O
.	O
</s>
<s>
Use	O
contrast	O
between	O
adjacent	O
pixels	B-Algorithm
to	O
heuristically	O
find	O
edges	B-Algorithm
,	O
and	O
determine	O
whether	O
the	O
edges	B-Algorithm
are	O
in	O
the	O
horizontal	O
or	O
vertical	O
directions	O
.	O
</s>
<s>
The	O
blend	O
direction	O
of	O
a	O
pixel	B-Algorithm
will	O
be	O
perpendicular	O
to	O
the	O
detected	O
edge	O
direction	O
on	O
that	O
pixel	B-Algorithm
.	O
</s>
<s>
Calculate	O
one	O
blend	O
factor	O
for	O
a	O
high-contrast	O
pixel	B-Algorithm
by	O
analyzing	O
the	O
luminance	O
data	O
in	O
the	O
3x3	O
grid	O
of	O
pixels	B-Algorithm
with	O
the	O
pixel	B-Algorithm
in	O
question	O
being	O
the	O
center	O
pixel	B-Algorithm
.	O
</s>
<s>
Blend	O
the	O
pixel	B-Algorithm
using	O
the	O
chosen	O
blend	O
direction	O
and	O
the	O
maximum	O
of	O
both	O
of	O
the	O
blend	O
factors	O
that	O
were	O
calculated	O
.	O
</s>
<s>
The	O
main	O
advantage	O
of	O
this	O
technique	O
over	O
conventional	O
spatial	B-Algorithm
anti-aliasing	I-Algorithm
is	O
that	O
it	O
does	O
not	O
require	O
large	O
amounts	O
of	O
computing	O
power	O
.	O
</s>
<s>
It	O
achieves	O
this	O
by	O
smoothing	O
undesirable	O
jagged	O
edges	B-Algorithm
(	O
"	O
jaggies	B-Algorithm
"	O
)	O
as	O
pixels	B-Algorithm
,	O
according	O
to	O
how	O
they	O
appear	O
on-screen	O
,	O
rather	O
than	O
analyzing	O
the	O
3D	O
model	O
itself	O
,	O
as	O
in	O
conventional	O
spatial	B-Algorithm
anti-aliasing	I-Algorithm
.	O
</s>
<s>
Since	O
it	O
is	O
not	O
based	O
on	O
the	O
actual	O
geometry	O
,	O
it	O
will	O
smooth	O
not	O
only	O
edges	B-Algorithm
between	O
triangles	O
,	O
but	O
also	O
edges	B-Algorithm
inside	O
alpha-blended	B-Algorithm
textures	I-Algorithm
,	O
or	O
those	O
resulting	O
from	O
pixel	B-Algorithm
shader	O
effects	O
,	O
which	O
are	O
immune	O
to	O
the	O
effects	O
of	O
multisample	B-Algorithm
anti-aliasing	I-Algorithm
(	O
MSAA	O
)	O
.	O
</s>
<s>
The	O
downsides	O
are	O
that	O
high	O
contrast	O
texture	O
maps	O
are	O
blurred	O
,	O
that	O
FXAA	B-Algorithm
must	O
be	O
applied	O
before	O
rendering	O
the	O
HUD	O
elements	O
of	O
a	O
game	O
lest	O
it	O
affect	O
them	O
too	O
,	O
and	O
that	O
polygonal	O
details	O
smaller	O
than	O
one	O
pixel	B-Algorithm
that	O
would	O
have	O
been	O
captured	O
and	O
rendered	O
by	O
MSAA	O
and	O
SSAA	O
cannot	O
be	O
captured	O
and	O
rendered	O
by	O
FXAA	B-Algorithm
alone	O
.	O
</s>
