Breaking Curves

This task shows you how to break curves. Curves can be broken by any combination of points, curves, planes and surfaces. See also Breaking Surfaces.
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 appear.

  2. Select the Break Curves option if needed:

    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.

      • Limitation: defines the set of limiting elements such as 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.
      • You can directly select an intersection curve resulting from a Cutting Plane Analysis as limiting element while breaking the surface.
      • If the Break Type is changed, the Elements and Limitation fields are cleared and the Elements field is highlighted for new element selection.

      • Break Both: breaks elements to be cut and limiting elements by each other.

    • Invert Selection: You can use this option to invert (move) the selection from the current state to the other state depending on the allowed selection type of the other state. For example, if, by mistake, you select three surfaces and one curve in Limitation state with Break Surface as the break type, and then just press the Invert Selection option to move all the three surfaces to the Elements state provided, the current state is Limitation. With this option, all the elements in the current state are moved to the other state. Note that the curve will not be moved to the Elements state, as selection of 1D elements is not allowed in the Elements state with the break type Break Surface. So the curve will remain in the Limitation state.

    • Disassemble: You can use this option to disassemble multi cell/domain bodies into mono cell bodies. When this option is unchecked, and you select a multi cell/domain body as Elements input and break it using a curve such that only one cell/domain is broken by this curve, the result should contain only two elements. But when this option is checked, the multi cell/domain results are disassembled into mono cell bodies.

    • 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”.
    • Break in to equal number: Only available in case of Break Curves break type. You can use this option to break an input curve/s into ‘x’ equal parts without selecting the Limitation inputs set. If you select a curve in the Elements input set and checks this option, the Limitation input selector will be inactive. Also, all the other options except relimitation options will be inactive. You have to specify the number parts you want to break each curve into, through the spinner provided. When you press the Apply button each curve will be broken into ‘x’ equal parts. Report shows the status for the cutting elements. In this option as there is no cutting element, report will always display “No computation done”.
    • Keep order with surface trim: In case of surface trim option, the maximum deviation, if any, between the original and the resulting outputs are shown in the dialog box as well as in the 3D. The command is migrated to the new common architecture for the Freestyle and Automotive Class A.
    • Trap Selection:  If you drag a trap in the model, all included elements will become selected. If no modifier was pressed, the current selection is emptied and only the included elements in the trap become selected. If CTRL is pressed while creating the trap, the included elements are added to the current selection.
      In case of selection by trap, only valid elements (surfaces in case of Break Surface and curves in case of Break Curves) are selected in the Elements and Limitation fields.
    • Stack command under Limitation:
      • When the Curves option is selected, the Limitation input editor is stacked with the following commands:
        • Create Point: On selection of input curve element, you can create an limiting point element directly by clicking on the curve or by using the Create Point contextual menu command. When you move the pointer over the curve, the pointer displays a red dot that helps you create the point. Using this you do not need to go via the contextual menu command of the Limitation field.

          Create Midpoint
        • Create Plane
        • Create Join
      • When Surfaces option is selected, the Limitation input is stacked with the following commands:
        • Create Plane
        • Create Isoparameter: On selection of input surface element, you can create an limiting Isoparameter element directly by clicking on the surface or by using the Create Point contextual menu command. When you move the pointer over the curve, the pointer displays a red dot that helps you create the point. You do not need to go via the contextual menu command of the Limitation field.  
        • Create 3D Curve
        • Create Join

    • Trim Type:

      • Edge Trim: curves are topologically relimited and the control points of the initial curves are kept.

      • Curve Trim: curves are geometrically relimited and the control points of the resulting curves are kept.

    • 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 (cutting element or element to be cut) along the tangent direction.

      • Curvature Extrapolation: extrapolates curve (cutting element or element to be cut) along the curvature direction.

      • Parametric Extrapolation: extrapolates curve (cutting element or element to be cut) along the parametric direction.

    • If there is an intersection between the cutting element and the element to be cut, the extrapolation options even if available, do not have any effect.
    • Using the Break Both option:
      • You can extrapolate the element to be cut.
      • The vertex of cutting element closest to the element to be cut, is used to extrapolate the cutting element, and vice versa.
    • If proper result is not obtained with this vertex, the vertex at other end of the respective element is used for extrapolation purpose.
    • In case of multi-domain cutting element, domain that has closest vertex to the element to be cut is used for extrapolation.

    •  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. This is available only with Break Curves and Trim Surface options.

  3. Select the curve.

    The element to be cut appears in the green color. 
     

  4. Select the Cutting field in the Break dialog box and select the surface and the curve as shown.

    The cutting elements appear in the red color.
     

  5. Click the Limitation List icon:

    The Limitation List dialog box appears. You can manage inside this dialog box the limiting elements: remove or replace.

  6. Click Close in the Limitation List 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. 

  7. Click Apply in the Break dialog box.

    Only the green elements are trimmed. By default, only one trimmed element is kept (plain line) other not (dashed line).
    After breaking the cut element (in green color) the part of element which is kept is shown by plain line and other not kept will be shown in dashed line.
     

  8. Click the curve segment to be kept: it appears with a plain line in the 3D geometry.

     

  9. 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.

  1. Click the Along Compass option:

  2. 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.
     

  3. Optional: In the Extrapolation area, select an extrapolation type.

    If element and limitation curves are not intersecting each other, they can be extrapolated. Use the options available in the Extrapolation area to specify the type of extrapolation. The intersection points are used to break the input curves.
    Each selected curve is provided with a point manipulator at its center to choose vertices of the curves for extrapolation.

    Each manipulator has 4 states:
    • Closest: Default. The closest vertices are extrapolated.
    • Start: A single-directional arrow manipulator pointing to the curve's start vertex is shown in addition to the point manipulator. The start vertex is extrapolated.
    • End: A single-directional arrow manipulator pointing to the curve's end vertex is shown in addition to the point manipulator. The end vertex is extrapolated.
    • Both: A bi-directional arrow manipulator pointing to both curve's start and end vertices is shown in addition to the point manipulator. Both vertices are extrapolated.
    The Start manipulator is reached by clicking on the point manipulator. A click on the start manipulator will change its direction to End and vice versa. Closest and Both manipulator states are reached through the contextual menu on the point manipulator.
    In case of multi-domain curve bodies, no manipulators are provided on the curves when selected. The closest domain of that body is considered for the extrapolation.

  4. Click on the element's point manipulator.

    An arrow manipulator is shown pointing in the direction of the curve's start vertex.

  5. Click Apply.

    The curve is extrapolated at its start vertex.

  6. Click OK in the Break dialog box.
  • You can select an edge of a surface, as the element to be cut. In this case, a new datum curve is created and is added to the selection.
  • If you select an edge of a surface as the cutting element, the Break Both option converts this edge into a datum curve.
  • You can extrapolate the non-intersecting curves and then break one element by other. Use the options available in the Extrapolation area to specify the type of extrapolation. The closest vertices of the selected elements are considered to extrapolate their respective curves. The intersection points are used to break the input curves.
  • 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.
  • 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.