Points, Knots, and Segments

The shape of a NURBS is controlled by its points, sometimes also called control points or control vertices (CVs). The points define segments and the segments are joined at knots.

In a linear curve, the segments are straight lines between the control points and the control points and knots overlap exactly.

In a cubic curve, the segments are interpolated between control points and the knots lie on the curve.

In a surface, the segments form knot curves in two directions (knot curves are sometimes called isoparams or isoparms). The knot curves intersect at the knots, forming four-sided patches.