<s>
In	O
3D	O
computer	O
graphics	O
,	O
normal	B-Application
mapping	I-Application
,	O
or	O
Dot3	O
bump	O
mapping	O
,	O
is	O
a	O
texture	O
mapping	O
technique	O
used	O
for	O
faking	O
the	O
lighting	O
of	O
bumps	O
and	O
dents	O
–	O
an	O
implementation	O
of	O
bump	O
mapping	O
.	O
</s>
<s>
A	O
common	O
use	O
of	O
this	O
technique	O
is	O
to	O
greatly	O
enhance	O
the	O
appearance	O
and	O
details	O
of	O
a	O
low	O
polygon	O
model	O
by	O
generating	O
a	O
normal	O
map	O
from	O
a	O
high	O
polygon	O
model	O
or	O
height	B-Data_Structure
map	I-Data_Structure
.	O
</s>
<s>
Normal	B-Application
maps	I-Application
are	O
commonly	O
stored	O
as	O
regular	O
RGB	O
images	O
where	O
the	O
RGB	O
components	O
correspond	O
to	O
the	O
X	O
,	O
Y	O
,	O
and	O
Z	O
coordinates	O
,	O
respectively	O
,	O
of	O
the	O
surface	O
normal	O
.	O
</s>
<s>
SIGGRAPH	O
1996	O
,	O
where	O
this	O
approach	O
was	O
used	O
for	O
creating	O
displacement	O
maps	O
over	O
nurbs	B-Algorithm
.	O
</s>
<s>
In	O
1998	O
,	O
two	O
papers	O
were	O
presented	O
with	O
key	O
ideas	O
for	O
transferring	O
details	O
with	O
normal	B-Application
maps	I-Application
from	O
high	O
to	O
low	O
polygon	O
meshes	O
:	O
"	O
Appearance	O
Preserving	O
Simplification	O
"	O
,	O
by	O
Cohen	O
et	O
al	O
.	O
</s>
<s>
However	O
object-space	O
normal	B-Application
maps	I-Application
cannot	O
be	O
easily	O
reused	O
on	O
multiple	O
models	O
,	O
as	O
the	O
orientation	O
of	O
the	O
surfaces	O
differ	O
.	O
</s>
<s>
Since	O
color	O
texture	O
maps	O
can	O
be	O
reused	O
freely	O
,	O
and	O
normal	B-Application
maps	I-Application
tend	O
to	O
correspond	O
with	O
a	O
particular	O
texture	O
map	O
,	O
</s>
<s>
it	O
is	O
desirable	O
for	O
artists	O
that	O
normal	B-Application
maps	I-Application
have	O
the	O
same	O
property	O
.	O
</s>
<s>
Tangent	O
space	O
normal	B-Application
maps	I-Application
can	O
be	O
identified	O
by	O
their	O
dominant	O
purple	O
color	O
,	O
corresponding	O
to	O
a	O
vector	O
facing	O
directly	O
out	O
from	O
the	O
surface	O
.	O
</s>
<s>
If	O
a	O
character	O
's	O
arm	O
is	O
bent	O
,	O
the	O
normal	B-Application
maps	I-Application
must	O
be	O
able	O
to	O
reflect	O
the	O
new	O
orientation	O
without	O
computationally	O
expensive	O
updates	O
to	O
texture	O
data	O
in	O
the	O
transform	O
.	O
</s>
<s>
The	O
tangent	O
is	O
part	O
of	O
the	O
tangent	O
plane	O
and	O
can	O
be	O
transformed	O
simply	O
with	O
the	O
linear	B-Algorithm
part	O
of	O
the	O
matrix	O
(	O
the	O
upper	O
3x3	O
)	O
.	O
</s>
<s>
Let	O
t	O
be	O
tangent	O
,	O
b	O
be	O
bitangent	O
,	O
n	O
be	O
normal	O
,	O
M3x3	O
be	O
the	O
linear	B-Algorithm
part	O
of	O
model	O
matrix	O
,	O
and	O
V3x3	O
be	O
the	O
linear	B-Algorithm
part	O
of	O
the	O
view	O
matrix	O
.	O
</s>
<s>
These	O
spatial	O
dimensions	O
are	O
relative	O
to	O
a	O
constant	O
coordinate	O
system	O
for	O
object-space	O
normal	B-Application
maps	I-Application
,	O
or	O
to	O
a	O
smoothly	O
varying	O
coordinate	O
system	O
(	O
based	O
on	O
the	O
derivatives	O
of	O
position	O
with	O
respect	O
to	O
texture	O
coordinates	O
)	O
in	O
the	O
case	O
of	O
tangent-space	O
normal	B-Application
maps	I-Application
.	O
</s>
<s>
Unit	O
Normal	O
vectors	O
corresponding	O
to	O
the	O
u	O
,	O
v	O
texture	O
coordinate	O
are	O
mapped	O
onto	O
normal	B-Application
maps	I-Application
.	O
</s>
<s>
Since	O
a	O
normal	O
will	O
be	O
used	O
in	O
the	O
dot	O
product	O
calculation	O
for	O
the	O
diffuse	O
lighting	O
computation	O
,	O
we	O
can	O
see	O
that	O
the	O
{	O
0	O
,	O
0	O
,	O
–	O
1}	O
would	O
be	O
remapped	O
to	O
the	O
{	O
128	O
,	O
128	O
,	O
255}	O
values	O
,	O
giving	O
that	O
kind	O
of	O
sky	O
blue	O
color	O
seen	O
in	O
normal	B-Application
maps	I-Application
(	O
blue	O
(	O
z	O
)	O
coordinate	O
is	O
perspective	O
(	O
deepness	O
)	O
coordinate	O
and	O
RG-xy	O
flat	O
coordinates	O
on	O
screen	O
)	O
.	O
</s>
<s>
Interactive	O
normal	O
map	O
rendering	O
was	O
originally	O
only	O
possible	O
on	O
PixelFlow	O
,	O
a	O
parallel	B-Operating_System
rendering	I-Operating_System
machine	O
built	O
at	O
the	O
University	O
of	O
North	O
Carolina	O
at	O
Chapel	O
Hill	O
.	O
</s>
<s>
It	O
was	O
later	O
possible	O
to	O
perform	O
normal	B-Application
mapping	I-Application
on	O
high-end	O
SGI	O
workstations	O
using	O
multi-pass	O
rendering	O
and	O
framebuffer	B-Algorithm
operations	O
or	O
on	O
low	O
end	O
PC	O
hardware	O
with	O
some	O
tricks	O
using	O
paletted	O
textures	O
.	O
</s>
<s>
However	O
,	O
with	O
the	O
advent	O
of	O
shaders	O
in	O
personal	O
computers	O
and	O
game	O
consoles	O
,	O
normal	B-Application
mapping	I-Application
became	O
widely	O
used	O
in	O
commercial	O
video	O
games	O
starting	O
in	O
late	O
2003	O
.	O
</s>
<s>
Normal	B-Application
mapping	I-Application
's	O
popularity	O
for	O
real-time	B-General_Concept
rendering	I-General_Concept
is	O
due	O
to	O
its	O
good	O
quality	O
to	O
processing	O
requirements	O
ratio	O
versus	O
other	O
methods	O
of	O
producing	O
similar	O
effects	O
.	O
</s>
<s>
mipmapping	B-Data_Structure
)	O
,	O
meaning	O
that	O
more	O
distant	O
surfaces	O
require	O
less	O
complex	O
lighting	O
simulation	O
.	O
</s>
<s>
Many	O
authoring	O
pipelines	O
use	O
high	O
resolution	O
models	O
baked	O
into	O
low/medium	O
resolution	O
in-game	O
models	O
augmented	O
with	O
normal	B-Application
maps	I-Application
.	O
</s>
<s>
Basic	O
normal	B-Application
mapping	I-Application
can	O
be	O
implemented	O
in	O
any	O
hardware	O
that	O
supports	O
palettized	O
textures	O
.	O
</s>
<s>
The	O
first	O
game	O
console	O
to	O
have	O
specialized	O
normal	B-Application
mapping	I-Application
hardware	O
was	O
the	O
Sega	B-Operating_System
Dreamcast	I-Operating_System
.	O
</s>
<s>
However	O
,	O
Microsoft	O
's	O
Xbox	B-Operating_System
was	O
the	O
first	O
console	O
to	O
widely	O
use	O
the	O
effect	O
in	O
retail	O
games	O
.	O
</s>
<s>
Out	O
of	O
the	O
sixth	B-Application
generation	I-Application
consoles	I-Application
,	O
only	O
the	O
PlayStation	B-Device
2	I-Device
's	O
GPU	O
lacks	O
built-in	O
normal	B-Application
mapping	I-Application
support	O
,	O
though	O
it	O
can	O
be	O
simulated	O
using	O
the	O
PlayStation	B-Device
2	I-Device
hardware	O
's	O
vector	O
units	O
.	O
</s>
<s>
Games	O
for	O
the	B-Operating_System
Xbox	I-Operating_System
360	I-Operating_System
and	O
the	O
PlayStation	B-Operating_System
3	I-Operating_System
rely	O
heavily	O
on	O
normal	B-Application
mapping	I-Application
and	O
were	O
the	O
first	O
game	O
console	O
generation	O
to	O
make	O
use	O
of	O
parallax	O
mapping	O
.	O
</s>
<s>
The	O
Nintendo	B-Operating_System
3DS	I-Operating_System
has	O
been	O
shown	O
to	O
support	O
normal	B-Application
mapping	I-Application
,	O
as	O
demonstrated	O
by	O
Resident	B-Application
Evil	I-Application
:	I-Application
Revelations	I-Application
and	O
Metal	B-Application
Gear	I-Application
Solid	I-Application
3	I-Application
:	I-Application
Snake	I-Application
Eater	I-Application
.	O
</s>
