<s>
OpenCTM	B-Application
is	O
an	O
open	B-Application
source	I-Application
project	O
that	O
has	O
evolved	O
around	O
a	O
technology	O
for	O
compressing	O
3D	O
triangle	B-Algorithm
meshes	I-Algorithm
.	O
</s>
<s>
An	O
open	B-Application
source	I-Application
software	I-Application
library	O
for	O
reading	O
and	O
writing	O
OpenCTM	B-Application
files	O
.	O
</s>
<s>
A	O
software	O
tool	O
set	O
for	O
converting	O
and	O
viewing	O
OpenCTM	B-Application
files	O
.	O
</s>
<s>
The	O
triangle	B-Algorithm
mesh	I-Algorithm
data	O
structure	O
that	O
OpenCTM	B-Application
uses	O
is	O
directly	O
compatible	O
with	O
high	O
performance	O
graphics	O
rendering	O
pipelines	O
,	O
such	O
as	O
OpenGL	B-Application
,	O
which	O
makes	O
is	O
suitable	O
for	O
interactive	O
computer	O
graphics	O
applications	O
.	O
</s>
<s>
Other	O
application	O
types	O
,	O
such	O
as	O
CAD/CAM	O
tools	O
,	O
usually	O
need	O
to	O
convert	O
the	O
mesh	O
data	O
into	O
a	O
custom	O
mesh	O
format	O
for	O
more	O
efficient	O
data	O
handling	O
.	O
</s>
<s>
OpenCTM	B-Application
uses	O
a	O
triangle	O
index	O
array	O
to	O
represent	O
the	O
triangle	O
connectivity	O
information	O
,	O
and	O
several	O
arrays	O
for	O
representing	O
vertex	O
data	O
(	O
vertex	O
coordinates	O
,	O
normals	O
,	O
UV	O
coordinates	O
and	O
custom	O
vertex	O
attributes	O
)	O
.	O
</s>
<s>
The	O
file	O
begins	O
with	O
a	O
special	O
integer	O
identifier	O
,	O
0x4D54434F	O
,	O
which	O
,	O
if	O
interpreted	O
as	O
four	B-Application
ASCII	I-Application
characters	I-Application
,	O
forms	O
the	O
string	O
“	O
OCTM	O
”	O
.	O
</s>
<s>
The	O
rest	O
of	O
the	O
file	O
,	O
which	O
is	O
described	O
in	O
the	O
file	O
format	O
specification	O
,	O
contains	O
the	O
triangle	B-Algorithm
mesh	I-Algorithm
information	O
.	O
</s>
<s>
Due	O
to	O
the	O
many	O
steps	O
of	O
data	O
processing	O
that	O
are	O
required	O
for	O
implementing	O
the	O
compression	O
,	O
interacting	O
with	O
the	O
file	O
format	O
directly	O
is	O
usually	O
more	O
complex	O
than	O
interacting	O
with	O
other	O
,	O
uncompressed	O
triangle	B-Algorithm
mesh	I-Algorithm
file	O
formats	O
(	O
for	O
instance	O
STL	O
and	O
PLY	O
)	O
.	O
</s>
<s>
LZMA	B-General_Concept
compression	O
library	O
.	O
</s>
