Projecting Curves

This task explains how to project curves on surfaces.

Open the ProjectCurve1.CATPart document.

  1. Select a curve.

  2. Click the Project Curve icon .

The Projection dialog box is displayed.


  1. Choose the projection orientation from the Projection dialog box:

  • Projection Normal to the Surface

  • Projection According to the Compass

  1. Press the Ctrl key and select the surface or set of surfaces on which the curve should be projected.

The projected curves are displayed, in dashed green, on the target surface along some information:

Projection according to
the compass orientation

Projection according to
the normal to the surface

The projected curves are BSplines lying on the surface. 
The Converter Wizard is automatically used to process the resulting curve and generate either a 2D NUPBS (Non Uniform Polynomial B-Spline) curve identified by the Exact text, or a 3D NUPBS curve (identified by Cv text).

If you wish to further control the projected curve, right-click the displayed text and choose the Edit contextual menu. The Converter Wizard is then explicitly launched allowing you to control the new curve creation.

For example, in the case of a 2D curve you may wish to generate a single segment curve by checking both the Segmentation and Single button in the Converter Wizard, then clicking OK.

  1. Click OK in the Projection dialog box to create the projected curves.
    If you chose the projection according to the compass orientation, two curves are created on the surface, and show up in the specification tree as two different elements.

  • When you project a curve on two surfaces, there may be no tangency continuity.

  • Use the Furtive Display icon to view the control points on the projected curve (in blue).

  • Check the Display Information option from the Converter Wizard's dialog box to the resulting curve's order and number of segments.
  • The element's topology (for example a relimited curve or surface) is taken into account for the projection.
  • Multi-selection of curves is allowed.
  • Multi-cell curves can be selected: the resulting projected curve will also be a multi-cell curve.
Available capabilities from the Dashboard are: keep original and Temporary Analysis.