Curve
Extend Curve
Extend Curve
By Line
By Arc
By Arc with Center
By Arc to Point
Curve on Surface
The Extend command lengthens or shortens a curve.
Steps
1.  Select a boundary object, type a length, or press Enter to extend without boundary edges. 


2.  Select a curve or an surface edge near the end. The extension will be automatically joined with the original curve. To extend to multiple objects, pick the end of the curve again to extend the curve beyond the first boundary to the next. 
3.  Pick the end of the extension or type a length. 
Note
●  You can use any combination of curves, surfaces, and solids as boundary edges. 
●  If you want to extend two curves to meet each other simultaneously, use the Connect command. 
Commandline options
Type
Natural
Lines, polylines, and polycurves with a line at the end to extend are extended by line.
Arcs and polycurves with arc at the end to extend are extended by same radius arc.
Other curves are extended smooth.
Makes an arc extension tangent to the original curve.
Arc Options
Extends a curve with an arc by picking the arc's center and endpoint.
Center steps
1.  Pick the arc's center point. 
2.  Pick the arc's end point. 
Extends a curve with an arc by picking the arc's endpoint.
ToPoint steps
Pick the arc's end point.
Makes a line extension tangent to the original curve.
Makes a smooth curve extension curvature continuous with the original curve.
Undo
The Undo option reverses the last action.
See also
Rhinoceros 5 © 20102015 Robert McNeel & Associates. 17Sep2015