<s>
Radiance	B-Application
is	O
a	O
suite	O
of	O
tools	O
for	O
performing	O
lighting	O
simulation	O
originally	O
written	O
by	O
Greg	O
Ward	O
.	O
</s>
<s>
It	O
uses	O
ray	B-Algorithm
tracing	I-Algorithm
to	O
perform	O
all	O
lighting	O
calculations	O
,	O
accelerated	O
by	O
the	O
use	O
of	O
an	O
octree	B-Data_Structure
data	O
structure	O
.	O
</s>
<s>
It	O
also	O
implements	O
global	B-Algorithm
illumination	I-Algorithm
using	O
the	O
Monte	B-Algorithm
Carlo	I-Algorithm
method	I-Algorithm
to	O
sample	O
light	O
falling	O
on	O
a	O
point	O
.	O
</s>
<s>
Greg	O
Ward	O
started	O
developing	O
Radiance	B-Application
in	O
1985	O
while	O
at	O
Lawrence	O
Berkeley	O
National	O
Laboratory	O
.	O
</s>
<s>
In	O
January	O
2002	O
Radiance	B-Application
3.4	O
was	O
relicensed	O
under	O
a	O
less	O
restrictive	O
license	O
.	O
</s>
<s>
One	O
study	O
found	O
Radiance	B-Application
to	O
be	O
the	O
most	O
generally	O
useful	O
software	O
package	O
for	O
architectural	O
lighting	O
simulation	O
.	O
</s>
<s>
The	O
study	O
also	O
noted	O
that	O
Radiance	B-Application
often	O
serves	O
as	O
the	O
underlying	O
simulation	O
engine	O
for	O
many	O
other	O
packages	O
.	O
</s>
<s>
Radiance	B-Application
defined	O
an	O
image	O
format	O
for	O
storing	O
HDR	O
images	O
,	O
now	O
described	O
as	O
RGBE	O
image	O
format	O
.	O
</s>
<s>
The	O
file	O
starts	O
with	O
the	O
signature	O
'	O
#	O
?	O
RADIANCE	B-Application
 '	O
and	O
then	O
several	O
lines	O
listing	O
the	O
commands	O
used	O
to	O
generate	O
the	O
image	O
.	O
</s>
<s>
As	O
produced	O
by	O
the	O
Radiance	B-Application
tools	O
this	O
always	O
takes	O
the	O
form	O
of	O
'	O
-Y	O
height	O
+X	O
width	O
.	O
</s>
<s>
Radiance	B-Application
calculates	O
light	O
values	O
as	O
floating	B-Algorithm
point	I-Algorithm
triplets	O
,	O
one	O
each	O
for	O
red	O
,	O
green	O
and	O
blue	O
.	O
</s>
<s>
But	O
storing	O
a	O
full	O
double	O
precision	O
float	B-Algorithm
for	O
each	O
channel	O
(	O
8	O
bytes	O
×	O
3	O
=	O
24	O
bytes	O
)	O
is	O
a	O
burden	O
even	O
for	O
modern	O
systems	O
.	O
</s>
<s>
The	O
first	O
scales	O
the	O
three	O
floating	B-Algorithm
point	I-Algorithm
values	I-Algorithm
to	O
share	O
a	O
common	O
8-bit	O
exponent	O
,	O
taken	O
from	O
the	O
brightest	O
of	O
the	O
three	O
.	O
</s>
<s>
The	O
second	O
stage	O
performs	O
run	B-Algorithm
length	I-Algorithm
encoding	I-Algorithm
on	O
the	O
32-bit	O
pixel	O
values	O
.	O
</s>
<s>
A	O
radiance	B-Application
scene	O
is	O
made	O
from	O
one	O
or	O
more	O
object	O
files	O
.	O
</s>
<s>
This	O
creates	O
a	O
chrome	B-Language
material	O
and	O
five	O
chrome	B-Language
spheres	O
spaced	O
20	O
units	O
apart	O
along	O
the	O
X-axis	O
.	O
</s>
<s>
Before	O
a	O
scene	O
can	O
be	O
used	O
,	O
it	O
must	O
be	O
compiled	O
into	O
an	O
octree	B-Data_Structure
file	O
( 	O
 '	O
.oct	O
'	O
)	O
using	O
the	O
oconv	O
tool	O
.	O
</s>
<s>
Most	O
of	O
the	O
rendering	O
tools	O
(	O
see	O
below	O
)	O
use	O
an	O
octree	B-Data_Structure
file	O
as	O
input	O
.	O
</s>
<s>
The	O
Radiance	B-Application
suite	O
includes	O
over	O
50	O
tools	O
.	O
</s>
<s>
They	O
were	O
designed	O
for	O
use	O
on	O
Unix	B-Application
and	O
Unix-like	O
systems	O
.	O
</s>
<s>
These	O
can	O
be	O
used	O
on	O
the	O
Unix	B-Application
command	O
line	O
and	O
piped	O
to	O
a	O
new	O
file	O
,	O
or	O
included	O
in	O
Radiance	B-Application
scene	O
files	O
( 	O
 '	O
.rad	O
'	O
)	O
themselves	O
,	O
as	O
shown	O
above	O
.	O
</s>
<s>
Several	O
radiance	B-Application
programs	O
manipulate	O
Radiance	B-Application
scene	O
data	O
by	O
reading	O
from	O
either	O
a	O
specified	O
file	O
or	O
their	O
standard	O
input	O
,	O
and	O
writing	O
to	O
standard	O
output	O
.	O
</s>
<s>
genworm	O
creates	O
a	O
worm	O
given	O
four	O
functions	O
-	O
the	O
(	O
x	B-Operating_System
,	O
y	O
,	O
z	O
)	O
coordinates	O
of	O
the	O
path	O
,	O
and	O
the	O
radius	O
of	O
the	O
worm	O
.	O
</s>
<s>
Radiance	B-Application
includes	O
a	O
number	O
of	O
programs	O
for	O
converting	O
scene	O
geometry	O
from	O
other	O
formats	O
.	O
</s>
<s>
nff2rad	O
converts	O
NFF	O
objects	O
to	O
Radiance	B-Application
geometry	O
.	O
</s>
<s>
obj2rad	O
convert	O
Wavefront	O
.obj	O
files	O
to	O
Radiance	B-Application
geometry	O
.	O
</s>
<s>
obj2mesh	O
convert	O
Wavefront	O
.obj	O
files	O
to	O
a	O
Radiance	B-Application
compiled	O
mesh	O
.	O
</s>
<s>
rpict	O
is	O
the	O
renderer	O
,	O
producing	O
a	O
Radiance	B-Application
image	O
on	O
its	O
standard	O
output	O
.	O
</s>
<s>
rvu	O
is	O
an	O
interactive	O
renderer	O
,	O
opening	O
an	O
X11	B-Operating_System
window	O
to	O
show	O
the	O
render	O
in	O
progress	O
,	O
and	O
allowing	O
the	O
view	O
to	O
be	O
altered	O
.	O
</s>
<s>
This	O
data	O
is	O
then	O
used	O
by	O
the	O
illum	O
material	O
modifier	O
to	O
make	B-Application
lighting	O
from	O
these	O
secondary	O
sources	O
more	O
accurate	O
and	O
efficient	O
to	O
compute	O
.	O
</s>
<s>
The	O
common	O
technique	O
to	O
achieve	O
anti-aliased	B-Algorithm
images	O
is	O
to	O
render	O
several	O
times	O
larger	O
than	O
the	O
desired	O
size	O
,	O
and	O
then	O
filter	O
the	O
image	O
down	O
using	O
pfilt	O
.	O
</s>
<s>
ximage	O
is	O
an	O
image	O
viewer	O
for	O
viewing	O
HDR	O
Radiance	B-Application
images	O
.	O
</s>
<s>
Previously	O
,	O
make	B-Application
and	O
a	O
makefile	O
were	O
used	O
in	O
a	O
similar	O
role	O
.	O
</s>
<s>
trad	O
is	O
a	O
GUI	O
front-end	O
to	O
rad	O
using	O
Tcl/Tk	B-Application
.	O
</s>
<s>
Greg	O
Ward	O
Larson	O
and	O
Rob	O
Shakespeare	O
,	O
Rendering	O
with	O
Radiance''	O
,	O
Morgan	O
Kaufmann	O
,	O
1998	O
.	O
</s>
