Insert SurfaceCapping

The Capping command enables you to fill "islands" or "holes" in surfaces or to create surfaces through curves, for example if you have a "wireframe" structure to be covered with surfaces.

After creating an initial filling surface, constraints can be added to it in order to modify its shape so that it matches your requirements. The shape of the initial surface can be selected in the Generic Shape drop-down list under More Options. The method can be Automatic, in which case the program will automatically choose the best type of filling surface among (portions of) a plane, a cylinder or a sphere. Otherwise you can explicitly specify the type of filling surface to be used: a portion of a plane to be defined ( Flat); a portion of a cylinder ( Single curvature) which you can specify the axis and radius of; a portion of a sphere ( Double curvature), to be defined through its center and radius; an Existing surface, in which case you will have to choose a Projection type suitable for the surface you selected. Final results depend on the chosen projection type and on the corresponding direction.

By choosing the corresponding item in the Constraint drop-down list ( Boundary curves, Internal curves, Internal points, Virtual vertices) you can set constraints about position, tangency and curvature continuity both along boundary curves and along internal curves. Constraints can also be defined for internal points.

• Boundary curves are optional: if you only specify internal curves and/or points, you will obtain capping surfaces through the specified curves/points not trimmed along the boundaries.
  Positional continuity is required among boundary curves belonging to the same group of selection (not required for internal curves). If more than one group of selection is defined for boundaries, positional continuity is required between groups, while you can select internal curves which are not closed.
• The Virtual vertices option is available so as to enable you to improve the shape of the resulting surface in certain cases of incompatibility. A virtual vertex is defined when two curves are supposed to "cross" each other without necessarily having real intersections. The said situation refers to positional incompatibilities, but virtual vertices can be used to solve tangency or curvature incompatibilities as well.
   
  

  Note Please note that virtual vertices are by no means a method to solve or even to bypass chaining issues along the boundaries: boundary curves always need to be correctly chained. The situations in which they can be profitably applied are described below.

  
  When the intersection among the selected curves (for example between a boundary curve and an internal curve) is not real, the surface you would get might not be as good as expected or required. In such a case, for example, using the Virtual vertices option can really help you improve the final result.

While the original objects remain unchanged, the result of the operation is the creation of a surface of the "GSM" type describing the new shape. A set of special options is provided to convert such surfaces into NURBS surfaces, in the case you need to export them to some environment different from think3.

Associativity The surfaces created using this command can be associative: associative surfaces are Skins, that is open solids, retaining a link to the base curves, so that if you modify the base curves the surfaces will be modified accordingly; they have a history and are displayed in the Model Structure. See " Associative Surfaces (Skins)" for details. Restoring selections after an interruption If you interrupt the Capping command, your selections and settings are not lost: they are "frozen" in order to enable you to use them again without having to repeat them all, which might take a long time, at least in complex situations. Next time you start the Capping command, in fact, the Restore Selection button ( ) will be displayed on top of the selection list. If you select the Restore Selection button ( ), all the selections you made and the settings you defined last time you used the command will be restored, enabling you to go on with no need to repeat those selections/settings. When the command is started with some pre-selected entities, if you click the Restore Selection button you will be asked to confirm restoring the frozen command selections, thus resetting the current selection. It is not possible to restore the frozen selection after the first use of the preview. Further details in "Restore Selection modality for selections and settings in curve and surface commands".

A set of Quality Checks commands is also available.

Try to ...

• Create a capping surface
• Use the Virtual vertices option of the Capping command
• Create a capping surface starting from an existing surface
• Define the shape of the initial surface
• Check your results
• Get NURBS surfaces instead of specialized ones
• Perform Quality Checks

Methodology articles related to this topic

• Warnings of the Capping command related to incompatibilities
• Modifying legacy surfaces with GSM