ViaCAD exports surfaces and solids into DWG files as precise NURBS and Solids, using embedded ACIS objects. Both AutoCAD and ViaCAD are based upon the ACIS kernel, which provides precise sharing of complex data. Unfortunately not all applications can understand these objects, which requires you to export your data as an AutoCAD R12 file. AutoCAD R12 is a pre-ACIS version so the precise objects are automatically tessellated into 3D facetted data. The 3D facetted data is supported by most applications that import DWG files.