JTF file format:

Offset    Description
------    -----------
  0       Magic bytes 74, 84, 70 and 33 ('JTF!')
  4       32bit integer for vertex format (must be 0)
  8       32bit integer for face count
  12      Triangles with 3*face_count vertices

  Each vertex is 8 32bit floats with 3 floats for position,
3 floats for normal and 2 floats for texture coordinates.
