Obj is a simple 3d file format. Antiryad Gx importer and exporter use extended format when importing and exporting Wavefront OBJ files to break some limitations.
Some new specifications are based on adoptions found on other softwares.

#Comment begin with sharp symbol.

#External material library.
#Library can be embedded in the OBJ file,
# in this case mtllib should reference an obj file (ex: current obj file name, this work with Blender 3d)
# instead of a mtl file [extension]
mtllib filename

#Animation frames per second [extension]
fps s

#Object
o [name]

#Object group
g [name]
  
#List of vertices
v x y z [w]
    
#Current vertex color, several colors per vertex is allowed [extension]
vc r g b a

#Current vertex joint weights (0.0 to 1.0), 4 weights per vertex are available [extension]
vw0 weight objectname\\
vw1 weight objectname\\
vw2 weight objectname\\
vw3 weight objectname\\

#List of texture coordinates 0
vt u v [w]

#List of texture coordinates 1 to 3 [extension]
vt1 u v [w]\\
vt2 u v [w]\\
vt3 u v [w]

#List of normals
vn x y z

#List of faces
f v/vt/vn v/vt/vn v/vt/vn ...

#Light [extension]
l name x y z r g b radius

#Animation of current object or light using position (x y z), axis pivot vector (vx vy vz)\\
and angle (a) in radian, repeat for each frames [extension]
a x y z vx vy vz a

#Current material to use
usemtl name

#Material
newmtl name

#Ambient color
Ka r g b

#Diffuse color
Kd r g b

#Specular color
Ks r g b

#Alpha (dissolve) factor
d f #f=[0.0;1.0]

#Illumination model
illum m #m=[0;10]

#Specular exponent
Ns v #v=[0.0;1000.0]

#Sharpness reflections
sharpness v #v=[0.0;1000.0]

#Ambient texture map
map_Ka [options] filename

#Diffuse texture map
map_Kd [options] filename #Generally same as map_Ka

#Specular texture map
map_Ks [options] filename

#Specular highlight texture map
map_Ns [options] filename

#Alpha texture map
map_d [options] filename

#Bump texture map
map_bump [options] filename
bump [options] filename

#Displacement texture map
disp [options] filename

#Stencil decal texture map
decal [options] filename