Extrapolating Surfaces

You can extrapolate a surface at one or several boundaries. Extrapolation is an operation in which an element is extended by a specified amount while respecting tangency or curvature conditions. Typically a surface boundary can be selected in order to extrapolate the surface for a specified length.

Note: The command is also available in the context toolbar.

Before you begin: Create a 3D shape containing a surface.
See Also
About Surface Extrapolation
In the Knowledge Base
Cases where the Extrapolate command cannot valuate the default support
  1. From the Transform section of the action bar, click Extrapolate .
  2. Pause over a boundary in the work area.

    The command automatically computes the geometrically feasible surface(s) that can be extrapolated. There are two possible scenarios:

    1. When only one surface is found, appears over the selected boundary, along with a tooltip. The tooltip contains information about the boundary and the surface, as follows: 
      Edge/Surface/Geometrical Set.1
SUPPORT:
Surface.1/Geometrical Set.1/Extrapolation Surface_Representation15498 --- IN_WORK

      Click the surface boundary.

    2. When the command finds more than one surface, appears. The accompanying tooltip indicates the boundary and its possible supports, one of which can be used as the surface to be extrapolated, as follows:
      Edge/Surface/Geometrical Set.1
POSSIBLE SUPPORT:
Extrapolate.1/Geometrical Set.2/Extrapolation Surface_Representation15498 --- IN_WORK
Surface.2/Geometrical Set.2/Extrapolation Surface_Representation15498 --- IN_WORK

      In this case, you can perform either of the following:

      • Right-click to display a list of all the possible surface solutions. Pause over one of the entries to display the corresponding surface in the work area. Click to confirm your selection.
      • Click the surface boundary. The command automatically selects the first entry from the list of possible surface solutions and computes the surface.

  3. Optional: In the Extrapolated box, select the surface to be extrapolated.

    Note: This step is only necessary if the command is unable to automatically compute the surface or if you want to manually select it.

    The surface selection appears in the Extrapolated box.
  4. In the Type list, select the extrapolation type.
    OptionDescription
    Length Enter the value in the Length box or use the handles in the work area.
    Note: It is recommended to enter a positive value.
    Up to element The Up to box is enabled. Select a plane or a surface that intersects the extrapolated surface to relimit the extrapolation.
  5. In the Continuity list, select Tangent.
    The selected surface and the extrapolation are connected with tangent continuity.

  6. In the Continuity list, select Curvature.
    The selected surface and extrapolation are connected with curvature continuity.

  7. Optional: To activate the approximate boundaries modem clear the Exact boundaries check box.

    This mode allows a more tolerant approach of the skin border reconstruction.

  8. Optional: Select the Deviation check box and specify a desired value in the box.

    In some cases, the extrapolation operation fails, due to creation of a gap between adjacent surfaces. The deviation value avoids creation of such gaps by considering a little difference between the obtained and theoretically calculated extrapolated surface result. This makes the extrapolation operation more robust. In case of a failure, an error message informs you about the required changes in the deviation value.

    Notes:
    • This check box is only available in curvature mode.
    • By default, when the Deviation check box is selected, the default deviation value is the point tolerance.

  9. Optional: In the Boundary box, select several boundaries.
    All surface sides are extrapolated applying the same type (Length or Up to element) and value (the length or the up-to element).

  10. In the Extremities list, select the extremities conditions between the extrapolated surface and the support surface.
    • Tangent: The extrapolation sides are tangent to the edges adjacent to the surface boundary.
    • Normal: The extrapolation sides are normal to the original surface boundary.


    Tangent extremity (and tangent continuity)

    Normal extremity (and tangent continuity)


    Tangent extremity (and curvature continuity)

    Normal extremity (and curvature continuity)
  11. In the Propagation list, select the propagation mode.
    OptionDescription
    Tangency continuity Propagates the extrapolation to the boundary's adjacent edges.
    Point continuity Propagates the extrapolation around all the boundary's vertices.


    No propagation

    Tangency propagation


    Point propagation
  12. Click OK.