<s>
Real-time	B-General_Concept
computer	I-General_Concept
graphics	I-General_Concept
or	O
real-time	B-General_Concept
rendering	I-General_Concept
is	O
the	O
sub-field	O
of	O
computer	O
graphics	O
focused	O
on	O
producing	O
and	O
analyzing	O
images	O
in	O
real	B-General_Concept
time	I-General_Concept
.	O
</s>
<s>
The	O
term	O
can	O
refer	O
to	O
anything	O
from	O
rendering	O
an	O
application	O
's	O
graphical	B-Application
user	I-Application
interface	I-Application
(	O
GUI	B-Application
)	O
to	O
real-time	O
image	B-General_Concept
analysis	I-General_Concept
,	O
but	O
is	O
most	O
often	O
used	O
in	O
reference	O
to	O
interactive	B-General_Concept
3D	O
computer	O
graphics	O
,	O
typically	O
using	O
a	O
graphics	B-Architecture
processing	I-Architecture
unit	I-Architecture
(	O
GPU	B-Architecture
)	O
.	O
</s>
<s>
Computers	O
have	O
been	O
capable	O
of	O
generating	O
2D	O
images	O
such	O
as	O
simple	O
lines	O
,	O
images	O
and	O
polygons	B-General_Concept
in	O
real	B-General_Concept
time	I-General_Concept
since	O
their	O
invention	O
.	O
</s>
<s>
Different	O
techniques	O
for	O
rendering	O
now	O
exist	O
,	O
such	O
as	O
ray-tracing	B-Algorithm
and	O
rasterization	O
.	O
</s>
<s>
This	O
means	O
that	O
the	O
user	O
can	O
respond	O
to	O
rendered	O
images	O
in	O
real	B-General_Concept
time	I-General_Concept
,	O
producing	O
an	O
interactive	B-General_Concept
experience	O
.	O
</s>
<s>
One	O
such	O
metric	O
is	O
the	O
number	O
of	O
frames	B-Algorithm
generated	I-Algorithm
in	O
a	O
given	O
second	O
.	O
</s>
<s>
Real-time	B-General_Concept
computer	I-General_Concept
graphics	I-General_Concept
systems	O
differ	O
from	O
traditional	O
(	O
i.e.	O
,	O
non-real-time	O
)	O
rendering	O
systems	O
in	O
that	O
non-real-time	O
graphics	O
typically	O
rely	O
on	O
ray	B-Algorithm
tracing	I-Algorithm
.	O
</s>
<s>
In	O
this	O
process	O
,	O
millions	O
or	O
billions	O
of	O
rays	O
are	O
traced	O
from	O
the	O
camera	O
to	O
the	O
world	B-Application
for	O
detailed	O
rendering	O
—	O
this	O
expensive	O
operation	O
can	O
take	O
hours	O
or	O
days	O
to	O
render	O
a	O
single	O
frame	O
.	O
</s>
<s>
Ray	B-Algorithm
tracing	I-Algorithm
is	O
far	O
too	O
slow	O
for	O
these	O
systems	O
;	O
instead	O
,	O
they	O
employ	O
the	O
technique	O
of	O
z-buffer	O
triangle	O
rasterization	O
.	O
</s>
<s>
In	O
this	O
technique	O
,	O
every	O
object	O
is	O
decomposed	O
into	O
individual	O
primitives	B-Algorithm
,	O
usually	O
triangles	O
.	O
</s>
<s>
These	O
triangles	O
are	O
then	O
decomposed	O
into	O
atomic	O
units	O
called	O
fragments	O
that	O
are	O
suitable	O
for	O
displaying	O
on	O
a	O
display	B-Device
screen	I-Device
.	O
</s>
<s>
GPUs	B-Architecture
and	O
other	O
advances	O
increased	O
the	O
image	O
quality	O
that	O
real-time	O
graphics	O
can	O
produce	O
.	O
</s>
<s>
GPUs	B-Architecture
are	O
capable	O
of	O
handling	O
millions	O
of	O
triangles	O
per	O
frame	O
,	O
and	O
current	O
DirectX	O
11/OpenGL	O
4.x	O
class	O
hardware	O
is	O
capable	O
of	O
generating	O
complex	O
effects	O
,	O
such	O
as	O
shadow	O
volumes	O
,	O
motion	O
blurring	O
,	O
and	O
triangle	O
generation	O
,	O
in	O
real-time	O
.	O
</s>
<s>
Cutscenes	O
are	O
typically	O
rendered	O
in	O
real-time	O
—	O
and	O
may	O
be	O
interactive	B-General_Concept
.	O
</s>
<s>
Real-time	O
graphics	O
are	O
typically	O
employed	O
when	O
interactivity	B-General_Concept
(	O
e.g.	O
,	O
player	O
feedback	O
)	O
is	O
crucial	O
.	O
</s>
<s>
In	O
real-time	B-General_Concept
computer	I-General_Concept
graphics	I-General_Concept
,	O
the	O
user	O
typically	O
operates	O
an	O
input	O
device	O
to	O
influence	O
what	O
is	O
about	O
to	O
be	O
drawn	O
on	O
the	O
display	O
.	O
</s>
<s>
Another	O
important	O
factor	O
controlling	O
real-time	B-General_Concept
computer	I-General_Concept
graphics	I-General_Concept
is	O
the	O
combination	O
of	O
physics	O
and	O
animation	O
.	O
</s>
<s>
These	O
techniques	O
help	O
realistically	O
imitate	O
real	O
world	B-Application
behavior	O
(	O
the	O
temporal	O
dimension	O
,	O
not	O
the	O
spatial	O
dimensions	O
)	O
,	O
adding	O
to	O
the	O
computer	O
graphics	O
 '	O
degree	O
of	O
realism	O
.	O
</s>
<s>
Real-time	O
previewing	O
with	O
graphics	B-Application
software	I-Application
,	O
especially	O
when	O
adjusting	O
lighting	O
effects	O
,	O
can	O
increase	O
work	O
speed	O
.	O
</s>
<s>
Some	O
parameter	O
adjustments	O
in	O
fractal	B-Algorithm
generating	I-Algorithm
software	I-Algorithm
may	O
be	O
made	O
while	O
viewing	O
changes	O
to	O
the	O
image	O
in	O
real	B-General_Concept
time	I-General_Concept
.	O
</s>
<s>
The	O
graphics	B-General_Concept
rendering	I-General_Concept
pipeline	I-General_Concept
(	O
"	O
rendering	B-General_Concept
pipeline	I-General_Concept
"	O
or	O
simply	O
"	O
pipeline	O
"	O
)	O
is	O
the	O
foundation	O
of	O
real-time	O
graphics	O
.	O
</s>
<s>
The	O
architecture	O
of	O
the	O
real-time	B-General_Concept
rendering	I-General_Concept
pipeline	O
can	O
be	O
divided	O
into	O
conceptual	O
stages	O
:	O
application	O
,	O
geometry	O
and	O
rasterization	O
.	O
</s>
<s>
This	O
includes	O
texture	O
animation	O
,	O
animation	O
of	O
3D	O
models	O
,	O
animation	O
via	O
transforms	B-Algorithm
,	O
and	O
geometry	O
morphing	O
.	O
</s>
<s>
Finally	O
,	O
it	O
produces	O
primitives	B-Algorithm
(	O
points	O
,	O
lines	O
,	O
and	O
triangles	O
)	O
based	O
on	O
scene	O
information	O
and	O
feeds	O
those	O
primitives	B-Algorithm
into	O
the	O
geometry	O
stage	O
of	O
the	O
pipeline	O
.	O
</s>
<s>
The	O
geometry	O
stage	O
manipulates	O
polygons	B-General_Concept
and	O
vertices	O
to	O
compute	O
what	O
to	O
draw	O
,	O
how	O
to	O
draw	O
it	O
and	O
where	O
to	O
draw	O
it	O
.	O
</s>
<s>
Usually	O
,	O
these	O
operations	O
are	O
performed	O
by	O
specialized	O
hardware	O
or	O
GPUs	B-Architecture
.	O
</s>
<s>
The	O
two	O
main	O
types	O
of	O
projection	O
are	O
orthographic	O
projection	O
(	O
also	O
called	O
parallel	O
)	O
and	O
perspective	B-Architecture
projection	I-Architecture
.	O
</s>
<s>
Perspective	B-Architecture
projection	I-Architecture
utilizes	O
the	O
concept	O
that	O
if	O
the	O
distance	O
between	O
the	O
observer	O
and	O
model	O
increases	O
,	O
the	O
model	O
appears	O
smaller	O
than	O
before	O
.	O
</s>
<s>
Essentially	O
,	O
perspective	B-Architecture
projection	I-Architecture
mimics	O
human	O
sight	O
.	O
</s>
<s>
Clipping	B-Algorithm
is	O
the	O
process	O
of	O
removing	O
primitives	B-Algorithm
that	O
are	O
outside	O
of	O
the	O
view	O
box	O
in	O
order	O
to	O
facilitate	O
the	O
rasterizer	O
stage	O
.	O
</s>
<s>
Once	O
those	O
primitives	B-Algorithm
are	O
removed	O
,	O
the	O
primitives	B-Algorithm
that	O
remain	O
will	O
be	O
drawn	O
into	O
new	O
triangles	O
that	O
reach	O
the	O
next	O
stage	O
.	O
</s>
<s>
The	O
purpose	O
of	O
screen	O
mapping	O
is	O
to	O
find	O
out	O
the	O
coordinates	O
of	O
the	O
primitives	B-Algorithm
during	O
the	O
clipping	B-Algorithm
stage	O
.	O
</s>
