Extend Curve

Functionality

This node generates a continuation of given Curve beyond it’s end points in a smooth manner. It can be used if you for some reason have just a segment of a curve, and want to continue it, for example, until it meets some plane or surface.

Inputs

This node has the following inputs:

• Curve. The curve to be extended. This input is mandatory.

• StartExt. This defines how far the curve should be extended beyond it’s starting point. Depending on Extend by parameter, this is measured either in terms of curve’s T parameter, or in terms of curve length. Default value is 1.0. If this input is set to 0.0, then no continuation will be generated beyond curve’s starting point.

• EndExt. This defines how far the curve should be extended beyond it’s ending point. Depending on Extend by parameter, this is measured either in terms of curve’s T parameter, or in terms of curve length. Default value is 1.0. If this input is set to 0.0, then no continuation will be generated beyond curve’s ending point.

Parameters

This node has the following parameters:

• Type. Extending curves type. The available options are:

  • 1 - Line. Extend the curve with straight line segments. The direction of lines is calculated accordingly to curve’s tangent directions at starting and ending point. Thus, it is guaranteed that the resulting curve will have continuous first derivative at the point where original curve is glued with it’s extension.

    

  • 1 - Arc. Extend the curve with circular arcs. Extension direction and arc radius is calculated from curve’s tangents. The plane where the arc will lie is calculated based on curve’s second derivatives at ending points. Thus, it is guaranteed that the resulting curve will have continuous first derivative at the point where original curve is glued with it’s extension.

    

  • 2 - Smooth - Normal. Extend the curve with segments of second order (quadratic) curves. The coefficients of curves are calculated based on original curve’s tangent and second derivatives directions at the ending points. Thus, it is guaraneed that the resulting curve will have continuous first and second derivatives at the point where original curve is glued with it’s extension.

    

  • 3 - Smooth - Curvature. Extend the curve with segments of third order (cubic) curves. The coefficients of curves are calculated based on original curve’s tangent, second and third derivatives directions at the ending points. Thus, it is guaraneed that the resulting curve will have continuous first, second and third derivatives at the point where original curve is glued with it’s extension.

    

  The default option is 1 - Line.

• Extend by. This defines the units in which values of StartExt, EndExt inputs is measured. The available options are:

  • Curve parameter. Inputs define the range of curve’s T parameter. Since coefficients of the generated extension curves are calculated automatically, the length of extension curves can be hard to predict from the input values. On the other hand, this option is the faster one.

  • Curve length. Inputs define the length of extension curves. Required ranges of curve’s T parameter is calculated numerically, so this option is slower.

    

  The default option is Curve parameter.

• Length resolution. This parameter is available in the N panel only, and only when Extend by parameter is set to Curve length. Defines the resolution value for curve length calculation. The higher the value is, the more precisely extension curves length will be equal to the specified inputs, but the slower the computation will be. The default value is 50.

Outputs

This node has the following outputs:

• ExtendedCurve. The original curve extended by one extension curve at the beginning and another curve at the end.

  

• StartExtent. Extension curve generated at the beginning of the original curve.

  

• EndExtent. Extension curve generated at the end of the original curve.

  

Example of usage

Build part of curve from points, and then extend it to additional length of 1 at the beginning and to additional length of 2 at the end:

• Vector-> Vector sort

• Curves-> Cubic Spline

• Curves-> Evaluate Curve

• Viz-> Viewer Draw

• Scene-> Objects In Lite