Microstation 8.5

See specific importing limits
 
PREPARE THE OBJECT FOR IMPORTING
  Load a simple project: C:\Programmi\Bentley\Workspace\Projects\Examples\Civil\dgn\dtm.dgn
The 3D terrain.
EXPORT
Select one or more objects with a multiple selection and from the menù File>Esporta>DGN,DWG,DXF
DXF
Recommended setting.
NOTE
   1. VERIFY FACES NUMBER
It is necessary that the number of faces is not superior to 64.000. If the Mesh has a superior number of faces, we suggest dividing it into different objects, that will then be selected and at the same time exported into a single file. A single file can contain up to 500 Mesh, each containing 64.000 tripled polygons.
   2. SET THE PIVOT
The coordinates 0,0,0 will be used by 3D GeniuX as the object’s Pivot. To centre the pivot point within 3D GeniuX use the Centre Object tool .
   3. MATERIALS AND UV MAPPING
It is possible to apply UV mapping and materials mapping because some exporting formats maintain these data, thus allowing 3D GeniuX to read them. 

If the textures are in the same folder as the 3D object, the software will load them automatically, otherwise if they are in different folders it will be necessary to reassign them to each single part, from the “Properties” window>Load Texture.

In some cases it will be necessary to adjust the base colour of the object inside the 3D GeniuX “Properties” window, setting the values to the white R=255, Y=255, B=255