The workflow that appeals to me most of all, and which is especially relevant if a simplification of the model is unnecessary, is to export as DWG from Inventor.
When opened in AutoCAD each part may then be assigned a layer.
Unlike with the other formats discussed in these blogs, the DWG may be inserted into a Revit Generic Model Family successively by layers.
All the solids on the layers selection set is imported into the Revit family as a single solid object.
Exploding the import results in Revit Geometry.
These objects can then be assigned their own materials.
Repeat the process and the next part of the Family can be created. A good way to coordinate the placement of successive imports and explosions would be to use “Auto – Origin to Origin” for the Positioning Option.
If it is a Revit Generic Model Family it can even be set to host rebar even if the material of the relevant solid geometry is not set to concrete!
Unfortunately Area, Fabric Area and Fabric Sheet Reinforcement can only be placed in Structural Walls and Floors, and not in Generic Models. The Reinforcement extensions will not be applicable to the generic model either. If these reinforcement tools were to be used it may be better to model the components in Revit.
The STL file export is also a CAD export, but bringing it directly into Revit results only in one solid object when exploded.
Alternatively IFC format can be used (Industry Foundation Class)
Some mapping of categories are provided.
Help on IFC files & Revit can be found here; http://help.autodesk.com/view/RVT/2017/ENU/?guid=GUID-C61C2E42-0561-48C9-8459-3EAC10EC8E16