If you have existing designs created using other CAD software, you can import or link them into a Revit project to use as a starting point for a building model.
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.
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.
An object in Revit must be assigned a category in order for Revit to know how to cut it, whether in plan or section. Geometry in a 3D DWG file imported or linked directly into a Revit project has no category assigned, and therefore will not be cut. For example, if you create a level at the elevation of a typical wall and then switch to a plan view, the imported geometry will not cut at that level. However, if you import the geometry into a cuttable family category (such as Generic Models), the geometry will cut in accordance with Revit’s cut planes.
To do this, you can use an in-place family from within a project, or create a new loadable family.
Import (you cannot use Link) your 3D DWG geometry into the family. You can use any of the cuttable family categories, but most likely the Generic Models category will meet your needs. After you load the family into the project, the imported geometry will cut according to the object styles assigned to the category used.