Use the NURBS Chain to Spline function to convert a chain of curves into a single spline. For instance, when a series of cross sections that would be used for a General Curve surface consists of more than one entity per cross section, or when there is an unequal number of entities per cross section, converting each chain into a single spline offers a simple solution.

Splines created with the chain to spline converter very closely model the original curves. However, one simple rule should be followed. Splines, like surfaces, should always be fair and smooth with no sharp corners. Therefore, any chain of entities to be converted into a spline should consist of entities that are tangent to each other at the end points.

To use this option, you must have prepared one or more chains of curves possibly consisting of lines, arcs, conics, and 3D splines, connected end-to-end, defining the shape of the desired splines. Each chain can be input, in sequence, prior to processing. This method of 'batch' processing facilitates the conversion of multiple chains with a minimum of processing time.

• Control Points can be modified through the Edit dialog that appears when a NURBS spline is selecting using the Generic Edit function.

• To reduce the number of nodes on the new spline, use the Spline Tolerance setting available from the File>Properties>Units/Tolerances dialog.

Using the Function:

1. Select NURBS Chain from the Create>Spline options. The Chain Curves into a Spline dialog box appears as shown below. If you want to delete the original curves leave the checkbox enabled.

2. Select the mode of selection to define the chain, either SINGLE or CHAIN.

3. Select the entities to define the chain.

4. Select ACCEPT/OK when finished to commence processing.