Extend Curve

Modify Curve Extend

The Extend Curve command enables you to modify the length of a selected curve by maintaining one of the following:

Its tangency continuity conditions at the selected end point.
Its curvature continuity conditions at the selected end point.
Its torsion continuity conditions at the selected end point.
Its curvature plot continuity conditions at the selected end point.
Its infinite continuity conditions at the selected end point, which means the length will be increased by augmenting the value of the parameter describing the curve in its parametric equation.
Its geometric tangency continuity conditions at the selected end point, that is this option enables you to modify the length of a selected curve by creating a straight-line extension tangent to the curve at one of its endpoints.

If the selected curve is a specialized curve, you will be asked to confirm whether you want to convert it into a NURBS curve (unless you have deselected the Ask before converting check box).

First select the curves to be modified (the Curves item in the selection list will turn to green) and then end selection by right-clicking and selecting Continue in the context menu. Pay attention to pick the curves close to the end point the modification must be applied to. Each curve is always extended — never shortened — and a new arc added to it. Tangent Extension

Once the command has been started and you have completed the selection of the curves to be modified you can choose the method in the Mode drop-down list.

Point
Specify a point: the part of the curve at the selected endpoint is extended to the point indicated or its projection according to the Continuity By: option selected.
Boundary
Specify a limit: the part of the curve at the selected endpoint is extended as far as its intersection with another selected entity according to the Continuity By: option selected.
Length
Specify the numeric value of the length: the part of the curve at the selected endpoint is extended as far as the specified length, according to the Continuity By: option selected.

Then, in the Continuity By: drop-down list, you can select the method to be applied in order to change the curve length (see "Continuity Types" for a general definition of the continuity types):

First derivative	Enables you to increase the length of the curve at the selected end point ensuring C-tangency at that point (C¹).
Second derivative	Enables you to increase the length of the curve at the selected end point ensuring C-curvature continuity at that point (C²).
Third derivative	Enables you to increase the length of the curve at the selected end point ensuring C-torsion continuity at that point (C³).
Fourth derivative	Enables you to increase the length of the curve at the selected end point ensuring C-Curvature plot curvature continuity at that point (C⁴).
Parameter	Enables you to increase the length of the curve by changing the value of the parameter that describes it (each curve is described trhough a parametric equation as a function of a u parameter whose value ranges from 0 to 1).
Tangency	Enables you to increase the length of the curve at the selected end point ensuring G¹ tangency continuity at that point.

The Associative Mode check box enables you to create curves which retain a link to the surfaces/curves they derive from.

	When the check box is selected, the resulting curves will be associative. The new curve will retain a link to the entities it derives from. A specific node displaying both the original entities and the resulting associative curve will be added to the Model Structure.
	When the check box is cleared, the resulting curves will not be associative.

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