How Accurately Can a Spherical Cap be Represented by Rational Quadratic Polynomials?

This paper discusses the incapability of a tensor product rational quadratic patch to accurately represent a spherical cap. It was analytically found that there is no combination of control points and associated weights to accurately represent the spherical cap. On top of that, an optimization technique has revealed that for a unit sphere the computed radii in the parametric space may reduce within the interval [0.999999994, 1.000104146]. This study makes sense as a preparatory stage in relation with the isogeometric analysis (IGA), which may be applied in conjunction with either the Finite Element Method (FEM) or the Boundary Element Method (BEM).