
all right, done more testing with the .obj on my side:
- if I reimport an .obj made with the native xsi exporter i get this:
it looks correct, the normals are unaltered. It is correctly read by Mudbox too.
- if I reimport an .obj made with the new exporter however all I get is a flat line

(same in Mudbox so it's not XSI)
so there is definitely something strange about the .obj normals output.
but be it with your plugin exported .obj or native .obj (manually loaded in octane) ... in Octane with both I get the same shading/smoothing error.
however if I manually import the .obj into octane (both native or plugin) and
unckeck the option "use OBJ normals if supplied" , it renders fine without errors.
thanks for your help anyway.