Creating Boundaries

This task shows how to create the boundary curve of a surface or the boundary point of a curve.

Open the Boundaries1.CATPart document.

  1. Click Boundary .

    The Boundary Definition dialog box appears.
  2. Use the combo to choose the Propagation type:

    • Complete boundary: the selected edge is propagated around the entire surface boundary.
    • Point continuity: the selected edge is propagated around the surface boundary until a point discontinuity is met.
    • Tangent continuity: the selected edge is propagated around the surface boundary until a tangent discontinuity is met.
    • No propagation: no propagation or continuity condition is imposed, only the selected edge is kept.
    You can select the propagation type before selecting an edge.
  3. Select a Surface edge.

    The boundary curve is displayed according to the selected propagation type.
    No propagation Tangent continuity
    Point continuity Complete boundary
  4. You can relimit the boundary curve by means of two elements.

    If you relimit a closed curve by means of only one element, a point on curve for instance, the closure vertex will be moved to the relimitation point, allowing this point to be used by other features.
  5. Click OK to create the boundary curve.

    The curve (identified as is added to the specification tree.
    You cannot copy/paste a boundary from a document to another. If you wish to do so, you need to copy/paste the surface first into the second document then create the boundary.

    About the Propagation Type

    • If you select the surface directly, the Propagation type no longer is available, as the complete boundary is automatically generated. 
    Provided the generated boundary curve is continuous, you can still select a limiting point to limit the boundary.
    Using the red arrow, you can then invert the propagation of the limited boundary.
    • If you select a curve which has an open contour, the Propagation type becomes available: choose the No Propagation type and select the curve again. The extremum points will define the boundary result.