The control points of the spline influence its curvature. Each control point is located at some distance from the visible curve of the spline. Together, all of a spline's control points are sometimes called the spline's control polygon. For example, if a spline has a degree of 2, each control point has a domain of influence of four consecutive knots on the spline. The control point influences the part of the spline between the first and last knot of its domain.
Every control point has a weight associated with it.
All weights must be positive and a larger weight causes the spline to move closer to its control point. The weights produced by the freeform tool are all equal to 1, but splines with unequal weights are sometimes used in CAD drawings. These splines are rational. The degree of a spline, the number of knots it has, the locations of its control points relative to each other, and the relative size of its weights all influence the appearance of the spline on the drawing page. A spline can be periodic or nonperiodic.