Creating Blend Curves

This task explains how to create a NURBS blend curve between two given curves.
This function generates a blend curve between two end points. You can select any geometry element for the end point, even surface edges, for example, or a position in the inner of a surface. The blend curve can be connected to the adjacent elements with position, tangent, or curvature continuity.

The user can dynamically interact with manipulators to define the end points of the blend curve.
Transition constraints can be defined (G0-G2).
In addition, in case of G1 or G2, tangent lengths can be controlled by arrow manipulators. Clicking on the tool's peak changes the direction of the tangent.
Open the BlendCurves.CATPart document.

  1. Click the Blend Curves icon .
    The 'Blend Curve' dialog box opens.
 

  1. Click on one end of each curve and click Apply.
    The Blend Curve and UI-Tools appear.

  1. Set the continuity to G1

  1. If you pull on handle at the end of the manipulator, you can vary the radius of the blend curve.

  1. With a click on the other middle handle of the manipulator you swap the direction of the tangent.

  1. Click OK to create the blend curve.
You can define the following options:
  • Curve 1,Curve 2: Selection of the two curve end points can be carried out between which the blend curve is to be generated.
  • Trim: The original curves will be trimmed at the end points of the connecting curve.
  • Curve 1 options, Curve 2 options
    • Continuity: The continuity conditions can be defined before creating the blend curve. Default setting is G1.
  • Link: The continuity conditions  of both curves can be linked.
 
Start Radius: Definition of a radius at the appropriate curve end. This option can only be activated for continuity G2. If a radius is specified, the manipulator at the appropriate curve end is no longer available.

Depending on the users choice of options, the segmentation of the result curve will change:

no radius value set  >  1-segment curve
1 radius value set  >  2-segment curve
2 radius values set  >  3-segment curve
 
Invert: Inverts the radius by using the negative value.
Definition of radius values at both curve ends
 
Mid Continuity: Continuity condition for the middle part of the connecting curve when a radius is defined.
This option is only available if 'Start Radius' is switched on.
Link: The continuity conditions  of both curves can be linked.
  Mid Continuity = G1

 Mid Continuity = G2
 
Direction: The tangent and curvature continuity can be adopted from any other curve. The position is adopted from the adjacent curve in either case. In the case of a matching between Curve 1 and Curve 2 where a clear direction is not determined, you can define a direction via this selection field or the contextual menu.
Limit: A new start point can be defined by selecting a point or curve.