Here's a few things that have come up lately regarding importing dwg data:
- Revit imports from Model Space unless there is nothing in Model
Space. It then asks if you'd like to import the stuff it finds in paper
- Revit only recognizes the World Coordinate System (WCS)
- Revit doesn't "see" AutoCAD points, doesn't snap to them, you'll see them but can't "use" them.
- Revit doesn't "see" or even show AutoCAD Xline or Ray elements.
- Save details as single cad files not composite "sheets" of
details. Single cad files can be added to individual drafting views and
added to sheets allowing Revit to keep track of the sheet and detail
numbers for us.
- Perfect world in Revit = no dwg files imported or linked, don't
rely on them forever, work toward native Revit details and detail
For Exporting to DWG Revit 2012 offers the ability to define Layer
Modifiers so that we can tell Revit to generate better layers for things
like supply air ducts versus return air ducts.
They've also added a short list of predefined standards to pull from
(technically based on the previously provided layer standard files, just
presented more obviously now):