See how the open source software Topmod could be integrated with Revit into your schematic design toolbox on the Everything Autodesk Revit & BIM blog. TopMod3d is a free, open source, portable, platform independent topological mesh modeling system that allows users to create high genus 2-manifold (watertight) meshes.
While we have seen people do similar work with Rhino scripting (and possibly Grasshopper) and ParaCloud, this tool seems way easier; if not as comprehensive and precise (with it’s non-NURBS basis).

Follow this link for more information.