A B-spline (Figure 19) is a piecewise parametric polynomial or rational curve described in terms of control points and basis functions. If the weights in the knots are equal then it is a polynomial spline. If not, then it is a rational function spline. If the Boolean "isPolynomial" is set to TRUE then the weights shall all be set to 1. A B-spline curve is a piecewise Bézier curve if it is quasi-uniform except that the interior knots have multiplicity "degree" rather than having multiplicity one. In this subtype the knot spacing shall be 1.0, starting at 0.0. A piecewise Bézier curve that has only two knots, 0.0, and 1.0, each of multiplicity (degree+1), is equivalent to a simple Bézier curve.<br/>