* The OBJ file format

OBJ is a file format for 3D models. It is line based with every line
starting with an identifier for what the line describes. A file looks like this:

``
# comment
o name of object

# list of vertices
v 1.000000 1.000000 -1.000000
...

# list of texture coordinates (0.0 to 1.0)
vt 0.875000 0.500000
...

# list of vertex normals
vn 0.0000 1.0000 0.0000
...

# face elements. these consist of indices of the previous groups. this face
# element consists of the fifth, third, and first vertex (first number), and
# these vertices are coupled with the first, second, and third texture
# coordinate (second number) as well as the first vertex normal (third
# number). note that these indices start on 1, not 0.
f 5/1/1 3/2/1 1/3/1
...
``
