Here we start with the parametric equations of the ellipse model, [math]x\left(\theta\right)=2.25\cdot cos\left(\theta\right)[/math] and [br][math]y\left(\theta\right)=3\cdot sin\left(\theta\right)[/math] , but adjust the [i]x[/i] coordinate with the factor [math]1+a\ast sin\left(\theta\right)+b\ast sin^2\left(\theta\right)[/math].