I,ve got the ODB++ spec, what is transferred is controlled by the software doing the post processing and valour (now Mentors) gateway. If you want height information then use IDF as this is the method of transferring mechanical data to a mechanical system (DXF). ODB++ has information on the layers, graphical representation, the connectivity (net list) and the component information, this information is used for PCB fabrication and assembly, such as pick and place and for bare board testing to a netlist. Any convertion of ODB++ or Gerebr to DXF gives a DXF version of the artwork or the assembly drawing it does not give a 3D picture, which with the reference to height is what I suspect the OP is after, if this is the case then he needs to look at IDF interfaceSome more information would be useful.