Curve: Extend 3D
Function
Extend an Edge in 3D space. If the Object Edge is a straight line, the extension is also a straight line. If the Object Edge is a curved line, the edge will be extended using a B-Spline curve.
Call
Geometry > Curve > Extend
3D 
<Extend Curve dialog box>
Select Object Edge
Select an Object Edge, which will be extended. Only an independent Edge can be extended. The target Shape changes depending on the type of the Edge selected.
<Extend 3D for Curve>
<When selected Object Edge is a curve>
Target Shape : To Point
In
case that a wire is selected as Object Edge, Target Vertex should be selected
as a extension point of the Object Edge. Object Edge will be extended
as B-Spline curve to Target Vertex.
Use Snap
When
a curved line is selected as the Object Edge, use Snap to assign a Target
Vertex.
Reverse
When Reverse is checked on, the start point of the Object Edge becomes extended to the Target Shape, rather than from the end point.
<Extend Curve for Line>
<When selected Object Edge is a straight line>
Target Shape : To Edge
If the selected Object Edge is a straight line, the Target Edge must be selected so that the Object Edge can extend and meet the Target Edge. This command fails to operate if the selected Object Edge does not meet the Target Edge after an extension.
