A few of the global Revit pros have had a crack at rationalizing an ellipse for use in Revit.  Zach Kron went conceptual, Phil Read trimmed his way around, and David Light played with circle-based segmentation.

What is my answer to this problem?  Simply don’t do it in Revit – do it in AutoCAD.  For some people, that solution may not be acceptable, and that’s ok.  I also realise that the AutoCAD haters will probably victimise me for it…oh well, do what works I say 🙂

Here is how I did it:
I make an ellipse in an AutoCAD file after setting the PELLIPSE variable to 1.  This means that AutoCAD creates the ellipse as a polyline, which means it contains arcs.  I then Import / Link this into Revit and simply ‘pick’ the arc segments to make a nice smooth elliptical form.

Here is a video:

My method is probably the easiest of the lot, but it is also probably the least ‘Revit-ee’ and the least parametric…