If you have existing designs created using other CAD software, you can import or link them into a Revit model to use as a starting point for your design.
In addition to using the Import CAD and Link CAD tools, you can import CAD files using drag-and-drop from Windows® Explorer onto a model, drafting, or sheet view of Revit.
You can mirror imported and linked CAD files. See Mirror Elements.
Suppose that you import an AutoCAD® drawing into Revit and then want to trace over walls in that drawing. As you place the cursor near the lines representing the walls, it can snap to the lines or the midpoint between the lines.
When you import 3D shapes using SAT or 3DM (Rhino) files, you can use the imported shapes as references for dimensioning, snapping, and aligning. See About Importing 3D Shapes.
Revit supports reading in proxy graphics from AutoCAD files. Proxy graphics are AutoCAD's representations of AutoCAD Architecture objects. Unlike AutoCAD Architecture objects, proxy graphics have no intelligence.
Proxy graphics can exist for many types of data in AutoCAD, including Mechanical Desktop (MDT) parts and AutoCAD Runtime eXtension (ARX) objects. If you set the Proxygraphics command to 1 in AutoCAD, Revit can then import ARX objects and AutoCAD Architecture objects (such as walls and floors) in the DWG or DXF file.
Revit can import DWG files containing subdivision surfaces and solids created in AutoCAD. Some complex subdivision meshes may fail to convert to a traditional solid or surface altogether, or generate a problematic solid or surface. Other highly complex SubD meshes may not import completely or at all.