<s>
In	O
the	O
field	O
of	O
3D	O
computer	O
graphics	O
,	O
Multiple	B-General_Concept
Render	I-General_Concept
Targets	I-General_Concept
,	O
or	O
MRT	O
,	O
is	O
a	O
feature	O
of	O
modern	O
graphics	B-Architecture
processing	I-Architecture
units	I-Architecture
(	O
GPUs	B-Architecture
)	O
that	O
allows	O
the	O
programmable	O
rendering	B-General_Concept
pipeline	I-General_Concept
to	O
render	O
images	O
to	O
multiple	O
render	B-General_Concept
target	I-General_Concept
textures	I-General_Concept
at	O
once	O
.	O
</s>
<s>
Introduced	O
by	O
OpenGL	B-Application
2.0	O
and	O
Direct3D	B-Application
9	O
,	O
MRT	O
can	O
be	O
invaluable	O
to	O
real-time	O
3D	O
applications	O
such	O
as	O
video	O
games	O
.	O
</s>
<s>
Before	O
the	O
advent	O
of	O
MRT	O
,	O
a	O
programmer	O
would	O
have	O
to	O
issue	O
a	O
command	O
to	O
the	O
GPU	B-Architecture
to	O
draw	O
the	O
3D	O
scene	O
once	O
for	O
each	O
render	B-General_Concept
target	I-General_Concept
texture	O
,	O
resulting	O
in	O
redundant	O
vertex	O
transformations	O
which	O
,	O
in	O
a	O
real-time	O
program	O
expected	O
to	O
run	O
as	O
fast	O
as	O
possible	O
,	O
can	O
be	O
quite	O
time-consuming	O
.	O
</s>
<s>
With	O
MRT	O
,	O
a	O
programmer	O
creates	O
a	O
pixel	O
shader	O
that	O
returns	O
an	O
output	O
value	O
for	O
each	O
render	B-General_Concept
target	I-General_Concept
.	O
</s>
<s>
This	O
pixel	O
shader	O
then	O
renders	O
to	O
all	O
render	B-General_Concept
targets	I-General_Concept
with	O
a	O
single	O
draw	O
command	O
.	O
</s>
<s>
To	O
do	O
this	O
in	O
real-time	O
,	O
MRT	O
is	O
used	O
to	O
store	O
the	O
required	O
information	O
for	O
the	O
lighting	O
calculations	O
in	O
multiple	B-General_Concept
render	I-General_Concept
targets	I-General_Concept
,	O
which	O
are	O
then	O
used	O
after	O
the	O
entire	O
scene	O
has	O
been	O
drawn	O
to	O
calculate	O
the	O
lit	O
final	O
image	O
.	O
</s>
<s>
Typically	O
one	O
render	B-General_Concept
target	I-General_Concept
holds	O
color	O
and	O
surface	O
information	O
of	O
objects	O
,	O
while	O
another	O
contains	O
the	O
surface	O
normals	O
and	O
depth	O
information	O
of	O
the	O
scene	O
which	O
are	O
used	O
to	O
calculate	O
the	O
reflection	O
of	O
light	O
.	O
</s>
<s>
Additional	O
render	B-General_Concept
targets	I-General_Concept
can	O
be	O
used	O
to	O
store	O
information	O
such	O
as	O
the	O
specularity	O
of	O
the	O
surface	O
and	O
ambient	O
occlusion	O
data	O
.	O
</s>
