<s>
Subsurface	B-Algorithm
scattering	I-Algorithm
(	O
SSS	O
)	O
,	O
also	O
known	O
as	O
subsurface	B-Algorithm
light	I-Algorithm
transport	I-Algorithm
(	O
SSLT	O
)	O
,	O
is	O
a	O
mechanism	O
of	O
light	O
transport	O
in	O
which	O
light	O
that	O
penetrates	O
the	O
surface	O
of	O
a	O
translucent	O
object	O
is	O
scattered	O
by	O
interacting	O
with	O
the	O
material	O
and	O
exits	O
the	O
surface	O
at	O
a	O
different	O
point	O
.	O
</s>
<s>
Subsurface	B-Algorithm
scattering	I-Algorithm
is	O
important	O
for	O
realistic	O
3D	O
computer	O
graphics	O
,	O
being	O
necessary	O
for	O
the	O
rendering	O
of	O
materials	O
such	O
as	O
marble	B-Application
,	O
skin	O
,	O
leaves	O
,	O
wax	O
and	O
milk	O
.	O
</s>
<s>
If	O
subsurface	B-Algorithm
scattering	I-Algorithm
is	O
not	O
implemented	O
,	O
the	O
material	O
may	O
look	O
unnatural	O
,	O
like	O
plastic	O
or	O
metal	O
.	O
</s>
<s>
To	O
improve	O
rendering	O
efficiency	O
,	O
many	O
real-time	B-General_Concept
computer	I-General_Concept
graphics	I-General_Concept
algorithms	O
only	O
compute	O
the	O
reflectance	O
at	O
the	O
*	O
surface*	O
of	O
an	O
object	O
.	O
</s>
<s>
Skin	O
is	O
a	O
good	O
case	O
in	O
point	O
;	O
only	O
about	O
6%	O
of	O
reflectance	O
is	O
direct	O
,	O
94%	O
is	O
from	O
subsurface	B-Algorithm
scattering	I-Algorithm
.	O
</s>
<s>
This	O
approach	O
,	O
combined	O
with	O
other	O
more	O
traditional	O
lighting	O
models	O
,	O
allows	O
the	O
creation	O
of	O
different	O
materials	O
such	O
as	O
marble	B-Application
,	O
jade	B-Language
and	O
wax	O
.	O
</s>
<s>
Potentially	O
,	O
problems	O
can	O
arise	O
if	O
models	O
are	O
not	O
convex	O
,	O
but	O
depth	B-General_Concept
peeling	I-General_Concept
can	O
be	O
used	O
to	O
avoid	O
the	O
issue	O
.	O
</s>
<s>
Similarly	O
,	O
depth	B-General_Concept
peeling	I-General_Concept
can	O
be	O
used	O
to	O
account	O
for	O
varying	O
densities	O
beneath	O
the	O
surface	O
,	O
such	O
as	O
bone	O
or	O
muscle	O
,	O
to	O
give	O
a	O
more	O
accurate	O
scattering	O
model	O
.	O
</s>
<s>
As	O
noted	O
at	O
the	O
start	O
of	O
the	O
section	O
,	O
one	O
of	O
the	O
more	O
obvious	O
effects	O
of	O
subsurface	B-Algorithm
scattering	I-Algorithm
is	O
a	O
general	O
blurring	O
of	O
the	O
diffuse	O
lighting	O
.	O
</s>
<s>
This	O
technique	O
was	O
pioneered	O
in	O
rendering	O
faces	O
in	O
The	O
Matrix	O
Reloaded	O
,	O
but	O
is	O
also	O
used	O
in	O
the	O
realm	O
of	O
real-time	B-General_Concept
rendering	I-General_Concept
techniques	O
.	O
</s>
<s>
By	O
lighting	O
the	O
unwrapped	O
mesh	O
in	O
this	O
manner	O
,	O
we	O
obtain	O
a	O
2D	O
image	O
representing	O
the	O
lighting	O
on	O
the	O
object	O
,	O
which	O
can	O
then	O
be	O
processed	O
and	O
reapplied	O
to	O
the	O
model	O
as	O
a	O
light	B-Data_Structure
map	I-Data_Structure
.	O
</s>
<s>
To	O
simulate	O
diffusion	O
,	O
the	O
light	B-Data_Structure
map	I-Data_Structure
texture	O
can	O
simply	O
be	O
blurred	O
.	O
</s>
<s>
The	O
amount	O
of	O
blurring	O
required	O
to	O
accurately	O
model	O
subsurface	B-Algorithm
scattering	I-Algorithm
in	O
skin	O
is	O
still	O
under	O
active	O
research	O
,	O
but	O
performing	O
only	O
a	O
single	O
blur	O
poorly	O
models	O
the	O
true	O
effects	O
.	O
</s>
