Hi Pilou, sorry I don't understand what the "without double edges" part means... ?

Back a while ago I did add an additional mode to that OBJ converter program, the original mode is that it converts one line for every edge in the mesh - the second mode is that it makes a closed polyline for every polygon in the mesh. That second mode is ready to be selected and converted to planar surface as long as the polygons were actually planar.

- Michael