Worksession with non-native files (DGN) scale files by 1000 without asking

Worksessions has previously been discussed in Discourse ( I have an issue with DGN-files which might be triggered by the solution on RH-37060?

When I open a DGN-file in Rhino 7 SR7 it display everything more-or-less correctly (except dimensions and hatches) and Rhino interprets the units of the file to be in meters, so I can work with the file right away. When I use File > Insert, File > Import - or File > Worksession to Attach the same DGN-file to an empty Rhino drawing in mm (using no template), everything is scaled by a factor 1000, without me being asked or given an option NOT to scale the drawing but only convert the units. A grid of 3000 mm ends up being 3000000 similar to if I was choosing YES to the question of scaling when using the Units command. Doing exactly the same in AutoCAD will give me a correct translation of the DGN-file in mm.


1m_modul.dgn (31.5 KB)
3m_modul+PaperSpace_A4.pdf (77.7 KB)
1m_modul-Default.dwg (26.8 KB)


Both AutoCAD (DWG) and Microstation (DGN) allow each Xref to be “Clipped” using a polygon or a rectangle. Similar it is possible to “WipeOut” areas of the Xref’s so you then can add new geometry.
It would be really nice to have the same two features in Rhino - and Rhino should be able to read it.

Both AutoCAD (DWG) and Microstation (DGN) allow for “cherrypicking” objects from an X-Ref and place them as a copy in the current drawing. In AutoCAD this picking-operation is called “NCOPY”.



Hello -
This is standard behavior as far as I can see - if you Import, the file units are already known and the incoming file is scaled to be the correct size, not the same number of units as the original; presumably you do not want the import of a file to change the units of the currently open file. Of you Open the dgn, then the units are set to whatever is in that file, there is nothing to break by setting the units.

Does that make sense or am I missing the point?


Hi Pascal. What makes sense for me the most is offering the user an option for scaling during worksession attachments similar to on import. Ideally an option to choose the final units imported to be fx mm (as in AutoCAD) and then only scale the imported geometry if in other units.
Since Rhino offers us no insight on the fileunits in an imported file, the software should never just scale by 1000x as the “default” behaviour.

Hi Tim - I think this is not what is happening - the object keeps its original size, but in the units of the file into which it is imported - is that not correct?


Hmm. I’m not quite sure since I only have access to AutoCAD 2020/2022 and Rhino 6/7/WIP. When I attach the DGN-files in AutoCAD they show perfect size in mm without me doing anything special to make that happen. I can attach a bunch of them and they share origin. When I OPEN one of the DGN files in Rhino, the units are interpreted (by Rhino) as Meters (as seen in the bottomline), but the units are in fact in mm. - When I open a Rhino-template in mm and use Worksession to attach the same DGN it is automatically scaled (by Rhino) by a factor of 1000 (converting M to the template’s mm).