1. A computer-implemented method of generating a three-dimensional CAD solid model, comprising: accepting a user's input comprising a primary curve; automatically determining a first radius by identifying a diameter line extending between first and second end-points of said open primary curve, and cutting said diameter line in half; automatically determining a second radius; automatically determining a third radius; and generating a solid ellipsoid three-dimensional CAD model based on said first radius, said second radius and said third radius.