How do I convert a DXF to a GEO file for Examine3D?

The Examine3D DXFGEO converter only supports 3D face and polyline entities.  If you have an AutoCAD model which consists of an edge-connected solid made up of 3D faces, it can be imported.  However, this is somewhat rare, and most people end up either constructing the model in Examine3D using polylines, or using Rhino to create the model.  In general, Rhino can create a good surface mesh; for more information, see "How to Create a Model in Rhinoceros 4.0 and Import it into Examine3D" and Tutorial 11.