Yes, that’s what I used until now. The problem is that the result is a curve with a lot of points.

Difficult to manipulate cleanly and not necessarily symmetric.

I also discovered that the closer you get to a square, n>8, that irregularities start popping up in the control points.

It’s been a year but I think I may have found a way to create a superellipse using a NURBS curve. Check out this document - “https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19970014211.pdf”

On the documents page 26 (PDF page 64) the author describes a method to generate a superellipse curve from a NURBS curve. It seems to work.

Would it be possible to implement this in Rhino ?

This is exactly what Dale described above. It’s an approximation done by making an ellipse and changing the weights so the point “h” in the paper is in the right place. If you get the V7 WIP, you can try testSuperEllFromExp. You have to type it out completely. It has the same interface as the Ellipse command but also prompts you for the exponent.

Thanks. Time to install v7 and check out it out.

Chris