The symmetric analogue of the polynomial power basis

Abstract

A new polynomial basis over the unit interval t∈[0,1] is proposed. The work is motivation by the fact that the monomial (power) form is not suitable in CAGD, as it suffers from serious numerical problems, and the monomial coefficients have no geometric meaning. The new form is the symmetric analogue of the power form, because it can be regarded as an “Hermite two-point expansion” instead of a Taylor expansion. This form enjoys good numerical properties and admits a Horner-like evaluation algorithm that is almost as fast as that of the power form. In a ddition, the symmetric power coeddicients convey a geometric meaning, and therefore they can be used as shape handles. A polynomial expressed in the symmetric power basis is decomposed into linear, cubic, quintic, and successive components. In consequence, this basis is better suited to handle polynomials of different degrees than the Bernstein basis, and those algorithms involving degree operations have extremely simple formulations. The minimum degree of a polynomial is immediately obtained by inspecting its coefficients. Degree reduction of a curve or surface reduces to drooping the desired high degree terms.