Since the process has changed somewhat this is a revision of my previous post.
The Revit Model Builder add-in acts as a layer between the Revit modeling environment, including the Family Editor, and a .CSV text file. (The Revit environment can include Vasari; however, this has not been tested.)
The text file, which can be viewed in Excel for study if necessary, creates a bridge to other applications. There is no restriction on these other applications since the Model Builder is only aware of the text file. Most of the work to date has been done with data generated from either Rhino-Grasshopper or a special C# Model Builder Tool which is a Windows program that serves as a template for custom computational projects. Ports have been proposed for other applications such as Processing, AutoCAD, ArchiCAD, or other applications. If these other applications are used, they will need to customized to create the .CSV output based on their own geometry or other algorithm, and a .DLL library is provided to make this easier.
The primary workflow is for one of these applications to output an Excel worksheet that follows the conventions described in the next section. Then, from an open Revit session, the Model Builder tool reads the Excel data and creates new geometry in Revit.
A secondary workflow is to create geometry in Revit, and then use the Model Builder to export data to a text file. This is useful as a means of creating sample data, which can be edited and then imported to generate new geometry. It can also be used as a way of transferring geometry from Revit objects as drafting or model lines into the Family Editor or another view. In the future this output may be used to create geometry in the non-Revit applications.