2011

Table Of Contents
The SPLINE command creates a type of curve known as a nonuniform rational
B-spline (NURBS). A NURBS curve produces a smooth curve between control
vertices or fit points. The spline on the left is drawn with fit points, and the
spline on the right is drawn with control vertices.
Close the spline so that the start and endpoints are coincident and tangent.
Splines are a critical tool for creating NURBS surfaces for 3D modeling. You
can revolve, loft, sweep, and extrude open and closed splines to create surface
objects.
NOTE Because periodic curves on page 2174 are not currently supported, 3D surfaces
created from closed spines may kink when reshaped.
Fit Points vs. Control Vertices
There are different drawing options available depending on whether you use
fit points or control vertices.
Fit Points (Interpolated) - Specify the knot parameterization and tolerance
settings, but not the degree setting (a degree 3 spline is always created).
Control Vertices - You can specify the tolerance and degree settings, but
not the knot parameterization.
To draw a spline with control vertices
1 Click Surface tab Curves panel Spline CV.
2 Click in the drawing area to create the spline.
3 When you are done, press Enter.
To draw a spline with fit points
1 Click Surface tab Curves panel Spline Knot.
2 Click in the drawing area to create the spline.
680 | Chapter 18 Draw Geometric Objects