ok i made a simple 6 point box and got this info:

Max2Obj Version 4.0 Mar 10th, 2001

mtllib ./box2.mtl
g

object Box01 to come ...

v  -35.7933578491 -5.9040594101 -0.0000002581
v  4.7970476151 -5.9040594101 -0.0000002581
v  -35.7933578491 36.1623611450 0.0000015807
v  4.7970476151 36.1623611450 0.0000015807
v  -35.7933578491 -5.9040575027 -39.8523979187
v  4.7970476151 -5.9040575027 -39.8523979187
v  -35.7933578491 36.1623649597 -39.8523979187
v  4.7970476151 36.1623649597 -39.8523979187

8 vertices

g Box01
f 1 2 4 3
f 5 7 8 6
f 1 5 6 2
f 2 6 8 4
f 4 8 7 3
f 3 7 5 1

6 faces

g

i understand the v is vertex and the f shows the lines between vertices.  (by the way the line numbering in the crimson editor is a great way to track vertex number.) 

but here's some other sample lines:

vt 0.36695 0.499049
vt 0.366495 0.503613
vt 0.366081 0.507879

....

vn -0.464828 -0.0285485 0.884941
vn -0.470744 -0.0381977 0.881442
vn -0.434739 0.0687812 0.897926

 ....

f 4680/2431/4680 2666/2427/2666 3087/816/3087 389/2432/389
f 3091/820/3091 3090/2433/3090 4680/2431/4680 389/2432/389
f 4680/2431/4680 3090/2433/3090 23760/14466/23760 23750/14462/23750

this info from a vic 3 head exported.  i tink the vt must be morphs?  but how would you know which vertex the morph is associated with?  and what is that wierd face info about?  it looks like it is describing the location in space of the vertices that connect...but the first and last digit of each set of 3 is identical>  so that can't be it....anyone?

gracias

I believe the vt,  vn, & f lines have to do with uv mapping. 

Example: a very simple plane before taking into a UV Mapping program:

g plane

v 0 0 0
v 10 0 0
v 0 10 0
v 10 10 0

vt 0 0
vt 1 0
vt 0 1
vt 1 1

vn 0 0 1
vn 0 0 1
vn 0 0 1
vn 0 0 1

f 1/1/1 2/2/2 4/4/4 3/3/3

After UV-mapping and changing it to a spherical mapping:

v 0.00000000 0.00000000 0.00000000
v 10.00000000 0.00000000 0.00000000
v 0.00000000 10.00000000 0.00000000
v 10.00000000 10.00000000 0.00000000

vt 0.02500000 0.02500000
vt 0.97500002 0.02500000
vt 0.97500002 0.97500002
vt 0.02500000 0.97500002

vn 0.00000000 0.00000000 1.00000000
vn 0.00000000 0.00000000 1.00000000
vn 0.00000000 0.00000000 1.00000000
vn 0.00000000 0.00000000 1.00000000

g plane

f 1/1/1 2/2/2 4/3/4 3/4/3

Have a look at this page http://www.royriggs.com/poser.html
Scroll down to "OBJ File Format" http://www.royriggs.com/obj.html

Probably the best written explanation I have seen.

v = vertex
vt = texture vertex  (UV)
vn = normal of vertex
f = facet (polygon)
fo = facet also
l = line (can also represent spline)
g = group (sets the group for the facets that follow)
usemtl = material (sets the material group for the facets that follow)
mtllib = references a corresponding .mtl file that contains basic material settings for each material group

f is followed by up to three references: v/vt/vn for each vertex of the polygon.

Think, I pulled that from memory (though I double checked the order of the vertex types for 'f'). :)

Robert

ETA: Go here for a PDF which is probably the most definitive format specification for Wavefront OBJ around: http://www.wotsit.org/search.asp?page=2&s=3d

wow thanks very thorough guys.

i like your tag robert.

gracias