NURBS
A NURBS curve: a B-spline of any degree with the knots, and optionally weights, given.
Syntax
NURBS degree,[points],[knots]
NURBS @id,degree,[points],[knots],[weights],layer
| Argument | Meaning |
|---|---|
| degree | The degree: 1 straight lines, 2 quadratic, 3 cubic. |
| [points] | The control points. |
| [knots] | The knot vector: as many numbers as points + degree + 1, never decreasing. |
| [weights] | A weight for each point (optional, or NIL: all 1). |
The id, layer and any settings after it are the element settings.
Examples
P4=[250,250]
NURBS 2,[P1,P4,P0],[0,0,0,1,1,1],[1,0.7071,1]
A circular-looking arc from P1 to P0 pulled up towards P4.
Notes
NURBS curves mostly come from imported files. To draw a smooth curve yourself, a BSPLINE or CUBICSPLINE works out its knots from its points.