Extrapolating Curves and Surfaces

The 'Extrapolation' command is available in two variants:

• Extrapolation (Feature): After having carried out the extrapolation, a Feature element 'Extrapolation.X' is inserted in the specification tree and the original elements are set to Hide mode.
• Extrapolation (Datum): With this command, the extrapolated elements remain datum elements.

1. Click the Extrapolation (Feature) icon or Extrapolation (Datum) icon.
   The Extrapolation (Feature) or Extrapolation (Datum) dialog box opens.

• Type:
  • Standard: Dynamic extrapolation at one surface side along two opposite edges.
  • Unequal: Dynamic extrapolation of a single edge.
  • Unequal Geo: Geometrical dynamic extrapolation of a single edge.
  • Factor: The geometry is extrapolated by a factor. For this extrapolation mode, the popup-menu Stretch Type and the text fields Factor and Range are used.
  • Global: Only for available for Extrapolation (Datum).
    Extrapolation of several surfaces at the same time. In this mode you can select one or multiple edges. A point manipulator appears at each edge. If the edges are connected with position (G0) continuity, the corresponding surfaces will be simultaneously extrapolated by dragging one of the manipulators.
    
    
• Elements: Specifies the elements to be extrapolated.
  • Extrapolation (Feature): Specifies only one element.
    For the very special topological constellation, where isoline bounded cells are arranged in a single chessboard-like domain (datum or feature), it is possible to extrapolate the complete domain. The extrapolation type Standard must be chosen. Manipulators will be available at the chessboard's corner vertices and at each cell along its boundary.
    If a corner of the chessboard is extrapolated, a new chessboard domain will be generated, provided that the extrapolation of each individual cell at the end again results in a valid topological configuration, i. e. the result satisfies the topological G0 tolerance tied to the feature.
  • Extrapolation (Datum): Specifies several elements and boundaries.
• Boundaries: Only available for Extrapolation (Feature).
  Specification of the boundaries (surface) and the end points (curve) to be extrapolated.
• Stretch Type: Only available for the extrapolation type Factor.
  • Factor: The modification is done via the definition of a value in the text field Factor and each time applied via clicking the Apply button.
  • Range: The modification is done dynamically via the slider Range.
• Options:
  • Both Sides: Only available for the extrapolation type Standard.
    The opposite end is extrapolated simultaneously.
• Reset: Only available for the types Standard and Unequal where extrapolation is dynamically carried out via manipulators. The original geometry will completely be restored. To partially restore geometry, a contextual command is available at the manipulators.

Manipulators and contextual commands

Manipulators are displayed at the corner/end points and in the middle of the edges/curves for executing a dynamic extrapolation with the types Standard and Unequal. A contextual command can be activated with the right mouse button providing options for partially or completely restoring the original geometry:

• Reset: Reset of a single edge. Depending on the selected manipulator handle, different actions can be carried out:
  • in the middle of the edge (type Standard): reset of edge position,
  • at a vertex (type Standard): reset of the corner point (U and V direction are simultaneously modified), or
  • at a vertex (type Unequal): reset of the selected direction (U or V).
• Reset all: Complete reset of the original geometry. All modifications will be undone. This option corresponds to the button Reset in the dialog box.