Breaking Surfaces

This task shows you how to break surfaces. Surfaces can be broken by any combination of curves, planes and surfaces. See also Breaking Curves.
Available functionalities from the Dashboard are:
Open the FreeStyle_Part_40.CATPart document.

  1. Click the Break Surface or Curve icon:
    The Break dialog box and the Tools Palette appears.

  2. Click the Break Surfaces option:

    The Break dialog box content has been modified according to the selected type.

    The Break dialog box displays the following information:

    • Break Type:

      • Break Curves: breaks the curves.

      •  Break Surfaces: breaks the surfaces.

    • Selection

      • Elements: defines the set of curves or surfaces to be cut.

        Elements List: displays the list of elements to be cut.

      • Limitation: defines the set of limiting elements: points, curves, planes or surfaces.
      • You cannot break a multi-cell body using a cutting element at the cell boundary.
        For example, it is not possible to break a multi-cell curve by a point on one of its cell boundary.
      • If the Break Type is changed, the Elements field is cleared and highlighted for new element selection.
      • You can directly select an intersection curve resulting from a Cutting Plane Analysis as limiting element while breaking the surface.
      • In case of selection by trap, only valid elements (surfaces in case of Break Surface and curves in case of Break Curves) are selected.

      Limitation List: displays the list of limiting elements. You can select the limiting elements or instantly create an isoparametric curve as a limiting element by clicking the surface to break, then position the curve using the manipulator.
      If you click anywhere near one of the edges of the surface to break, the isoparametric curve is created normal to the nearest edge.
      By selecting the       Propagate option from the contextual menu of the manipulator you can propagate the isoparametric curve on to adjacent surfaces if selected in the Break dialog box. Clearing the Propagate Isoparametric Curve contextual command before creating an instant iso-parametric curve avoids propagation of iso-parametric curve on to adjacent surfaces. For more information about the isoparametric curves, see Creating Associative Isoparametric Curves.

      • Break Both: breaks elements to be cut and limiting elements by each other.
      • Fragments: fragments an input curve(s) or surface(s) without selecting the Limitation inputs set. If you select a curve(s) or surface(s) in the Elements input set and checks the Fragment option, the Limitation input selector would be inactive. Also, all the other options will be inactive. Now when you press the Apply button the curve(s) or surface(s) will be broken by its segment boundaries. Report shows the status for the cutting elements. In this option as there is no cutting element, report will always display “No computation done”.

    • Trim Type:

      • Face Trim: surfaces are topologically relimited and the control points of the initial surfaces are kept.

      • Surface Trim: surfaces are geometrically relimited and the control points of the resulting surfaces are kept.
        Only 4 edge-patches are created with Surfaces by curves option.

    • Order

      • U: defines the U order.
        Available only with Break Surfaces and Surface Trim options.
        The U and V order maximum values are set with the Order setting option of the FreeStyle settings.

      • V: defines the V order.
        Available only with Break Surfaces and Surface Trim options.
        The U and V order maximum values are set with the Order setting option of the FreeStyle settings.

    • Projection: By default the points that do not lie on the trimmed elements will not be projected onto the trimming elements.

      • Along Compass: projects along the compass direction.

      • Along Normal: projects along the normal direction.

      • Along Viewing Direction: projects along the viewing direction.

    • Extrapolation: The following extrapolation options are available:

      • Tangential Extrapolation: extrapolates curve along the tangent direction.

      • Curvature Extrapolation: extrapolates curve along the curvature direction.

      • Parametric Extrapolation: extrapolates curve along the parametric direction.

      •  IsoUV Extrapolation: extrapolates curve along the isoparametric U direction or isoparametric V direction. 4-directional arrow manipulators are provided to choose the iso direction.

    • The curve can be a cutting element or an intersection curve between surfaces of the cutting element and the element to be cut.
    • Extrapolation is done from both sides of curve.
    • If there is no intersection between surfaces of the cutting element and the element to be cut, the extrapolation options even if available, do not have any effect.
    • You can select an edge of a surface, as the element to be cut.

    • Report: displays a status about cutting elements:

      • Cutting elements that can be used for the Break (marked by a green tip). When you click on the text, the corresponding curve is highlighted in green in the 3D geometry.

      • Cutting elements that cannot be used for the Break (marked by the condition to be applied so that they can be used: projection, etc). When you click on the text, the corresponding curve is highlighted in red in the 3D geometry.

        • When there is no selection of cutting elements, an error message is issued and the Break Report panel informs you that no element is selected.

        • When a red cross is displayed, it means that the problem cannot be managed by the application.

    • Max deviation: displays the maximal deviation between original surface and the resultant surface in the dialog box and on the geometry.
      Available only with Break Curves and Trim Surface options.

  3. Select the surface.

  4. Select the Limitation field in the Break dialog box and select the six curves as shown.
     
    • In case the limiting elements are unavailable, you can click on the surface to create an isoparametic curves on the surface. You can move the isoparametric limiting curve using the manipulator and also propagate the curve on to adjacent supports (surface) selected in the break dialog box.
    • Right-click on a Limitation tag to quickly access contextual options for Extrapolation and Projection which are also available in the dialog box, as well as Propagate Isoparametric Curve and Assemble.

     

  5. Click Apply in the Break dialog box.
    The surface has been trimmed. By default, only one trimmed element is kept (no transparency has been applied) other not (a transparency has been applied).

  6. Click the curve segment to be kept: it appears with no transparency in the 3D geometry.

  7. Right-click any relimited element to display the following contextual menu.
    • Keep all: all parts of the all curves are kept.
    • Keep all but this: all parts of all curves are kept except the selected one.
    • Remove all but this: all parts of all curves are removed except the selected one.
    To keep, or do not keep, some elements press the Ctrl key and click them.

  8. Click Along Compass .

  9. Click Apply in the Break dialog box.
    Elements that do not lie on the trimmed elements will be projected (pseudo-intersections) onto the trimming elements according to the compass direction.

  10. Click Along Normal .

  11. Click Apply in the Break dialog box.
    Elements that do not lie on the trimmed elements will be projected (pseudo-intersections) onto the trimming elements according to the normal direction. The surface has been trimmed.

  12. Click the Shorten Mesh option:

  13. Click Apply in the Break dialog box.
    • The maximal deviation is displayed in the Break dialog box and on the geometry (yellow label).
    • The maximum degree variation allowed for each patch of the new surface as compared to patches of the initial surface can be modified.
    • Click the U Order and the V Order text to edit and modify the values (besides is an example with U and V values set to 8).

  14. Click the Tangential Extrapolation option: .

  15. Click Apply in the Break dialog box.
    As a consequence, one edge is added.

  16. Optional: Click the IsoUV Extrapolation option.

  17. Click Apply.
    The input elements are trimmed by extrapolating the limiting elements. By default, the shortest Iso side in U direction is taken to trim the surface.

    4-directional arrow manipulators are provided at the end points of the limiting elements for selecting any of the Iso-extrapolated sides to trim the surface in both IsoU and/or IsoV direction.

  18. Click one or more arrows to select the required Iso side(s).
    You see the trim result in the direction of the clicked arrow manipulators.

    • Undo/Redo is provided for arrow manipulator selection.
    • Arrow manipulators are provided only if extrapolation is required in case of IsoUV Extrapolation option.

  19. Click OK in the Break dialog box.
    Keep Original option setting in the Tools Dashboard is locally saved for the Break command when the command is exited by clicking OK. When you re-launch the Break command, the previous session's Keep Original option setting is available.

When the command fails to break input elements, it displays appropriate message stating the reason of failure. It also provides a report suggesting the proper action that need to be taken for successfully completing break operation.
 

Assemble


The Assemble contextual command temporarily joins the selected limiting elements. This command is available in the graphics area.

Consider the following two cases:
  • If you want to split the patch surface with the two non intersecting limiting elements (Curve.1 and Curve.2) as shown below:

    In this case, right-click the limiting elements in the graphics area and select Assemble to join them. It forms a single entity for extrapolation to get the expected result.
  • If you want to split a surface with the limiting elements and there is a small gap (<100 * resolution) between these elements as shown below:

    In this case, right-click the limiting elements in the graphics area and select Assemble. The limiting elements connect with each other to get the expected result.
By default, this option is selected.
 

Propagate


You can use the Propagate contextual command to select all the elements which are connected to the current selected limiting element.  

Consider a case where you want to split the below surface with all the curves as limiting elements.
 

Select any one curve in the Limitation box and apply the Propagate contextual command to select all the curves which are connected with point continuity to this curve.