Matching Curves

This task explains how to match a curve with another curve, a point on curve or a 3D point.

Open the FreeStyle_Part_44.CATPart document.

  1. Select the curve you wish to match to another curve.

  1. Click the Match Curve icon .

The Match Curve dialog box is displayed.

  1. Select the second element (first reference element) for the match curve to be joined to. It can either be:

  1. a curve

  2. a point on curve with history

  3. a datum point on curve

  4. a 3D point

  5. a vertex

The first curve is automatically modified so as to be connected to the second element while taking the continuity type into account. 

The number displayed on the first curve (Nx) corresponds to number of control points on that curve.



1. Match between a curve and another curve

2. Match between a curve and a point on curve with history



3. Match between a curve and a datum point on curve

4. Match between a curve and a 3D point




5. Match between a curve and a vertex

  • If you select a second reference element, both ends of the curve can be matched.

  Two tags for each reference element are displayed near the matching curve extremities. Only one reference element is current, meaning that you can only manipulate the second extremity of the matching curve, while the other extremity is fixed. To be able to select another reference element to perform another match, you must click the corresponding tag.

To deselect the first reference element, you need to perform a local undo.
  • If a curve is selected as the second element, all continuities can be applied (point, tangent, and curvature continuities)
  • If a curve or a point on curve with history is selected as the second element, a point or curvature continuity can be applied.
  • If a datum point on curve, a 3D point, a vertex is selected as the second element, a point continuity will be applied.
  • If the second element to match (a point on curve with history, or a vertex) lies one more than one support, the appears.
    Refer to the Selecting a Support chapter for further information.

  • The Project End Point option allows a linear projection of the minimum distance between two curves by projecting the initial curve onto the target curve.
  • The Quick Analysis option enables to perform a violation diagnosis of the curve matching. The original degree is kept (it is no more automatically increased). Several parameters are taken into account between the two curves:
    • distance 
    • continuity degree
    • curvature difference
  1. Click OK in the Match Curve dialog box to create the matched curve as it is previewed.

  If you select a frozen curve (a curve with an history) or a non-Nurbs curve as input, a dialog box is issued warning you that an automatic conversion will be automatically performed before the matching operation:
- if an exact conversion is possible, a new Nurbs curve will replace the input one in order to perform the match. This new curve will be added in the specification tree.
- if there is a deviation or no exact conversion exists, the Converter Wizard panel appears allowing you to define the approximation according to a tolerance using parameters such as U, V orders, patch numbers and deviation tolerance.
If a continuity type leads to some inconsistencies regarding the curve's original degree, a warning message is issued.

In order to reach the correct degree (0 or 180 degree) and percentage (0%), you can either:

- increase the number of control points by clicking the number (the value is increased by one) or by selecting a number from the contextual menu, or


- modify the continuity type by clicking it (it is displayed sequentially) or by selecting a type from the contextual menu.


Working with the FreeStyle Dashboard

  1. Make sure the Continuity icon is active in the Dashboard and, right-click onto the identifier to edit the continuity constraint, using the contextual menu.


You can choose from the point, tangency or curvature continuity type to be taken into account.


  1. Make sure the U, V orders icon is active in the Dashboard so that the numbers of control points are displayed.


  1. Make sure the Contact Points icon is active in the Dashboard, to display the point manipulators and to move the points along the curve, thus interactively redefining the connection location.


  1. Make sure the Tensions icon is active in the Dashboard, and modify the tension by sliding the displayed value along the green segment.


This segment represents the direction and limits of the match curve tangent at its end-points.


  1. Click OK in the Match Curve dialog box to create the matched curve as it is previewed.


  1. When working in P2 mode, click the Break Surface or Curve icon and select the curve to be broken.


  1. Select the side to be removed.


  1. Click OK in the Break Options dialog box.

    A new split curve is created replacing the initial one.


The curve resulting from the match remains selected by default. If you wish to perform analyses, make sure you select the other curve using the Control key.
Available capabilities from the Dashboard, and/or specified through the FreeStyle Settings, are: Temporary Analysis, Keep original, auto detection (Snap On Vertex option only), attenuation continuity, contact points, tensions, and furtive display.