Visible Edges DGN Files
You can create a visible edges DGN file — a 2D or 3D DGN file that contains the edges visible in a 3D view (that is, with those edges that would be hidden, removed).
Tip: Rather than creating a visible edges DGN file, the preferred technique in the context of the Drawing Composition workflow is to merge references into the active model. To merge references, select in the References dialog.