[quote]
Note the part that I have put in bold - it is intended that when vertex normals are present in the OBJ file, they are used to shade the polygon and smoothing groups are completely unused and should not affect the rendering in any way.
If you read the vertex normals from the file, all the normals for every face are already defined and there is nothing you need to do with smoothing group processing.
Just take the normals that the face is using and use them.... Don't modify them by break angles or smoothing groups or anything like that.
Maybe you are using a completely different term for what "vertex normal" is or something?

- Michael
[/quote]

you are correct only if you actually supply duplicates with different vertex normals of the vertices that are shared between polygons with a high angle, like the edgesplit solution.
if you supply only one vertex, you need to use the smoothing groups to differentiate.

sorry, i don't want to sound like mr know it all, but that's the way it is.
you should consider adding an option to your OBJ exporter that splits objects, eg duplicates vertexes shared on high angles (eg > 30 degrees or so), like the edgesplit solution.
however, if you just write what you do now, it will render fine once my smoothing group implementation is finished.

Radiance