Menu Structure: Curve

This menu item is for specifying and displaying curve segments. The supported curve types are Bézier, rational Bézier, B-spline and NURBS curves, where different curve types have slightly different options. Once a curve type is selected, its type is displayed in this item.

Knot Vector

The left side of the vertical slider in the drawing canvas is used to display the knot vector. The following figures, from left to right, show the knot vectors of an open, a clamped and a closed B-spline curve of degree 4. In the display, a knot is shown as p(q), where q is the knot value and p is its multiplicity. For example, in the knot vector of the open B-spline curve, 1(0.760) means 0.760 is a knot whose multiplicity is 1 (i.e., 0.760 is a simple knot). In the knot vector of the clamped B-spline curve, the clamped knots are 4(0.000) and 4(1.000) which means knots 0 and 1 are of multiplicity 4. For a closed B-spline and NURBS curve, several knots near 0 and 1 are shown in a different color, which means they cannot be modified (i.e., fixed to make the curve closed).