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The Draw->Open/Close command in the Model module allows you to open or close a curve or surface. In some cases, you must close a curve before you can perform some other operation, such as before converting a curve to a face.
Note:
You cannot open or close a trimmed NURBS Surface. For more information, see the note and procedure on NURBS Surfaces.
With the exception of Cardinal and B-Splines, curves and surfaces are closed or opened at the joining point of the u or v direction (point 1), shown by choosing Show->Edge Flags.
You can also close or open a curve or surface using the Effect->Curve Controls command, as well as shifting the point in u or v at which it is open or closed. Shifting offsets the start and end points of the curve; for example, point 0 is offset so that the beginning of the curve or surface changes according to the setting. By shifting this joining point, you shift the spot of opening or closure.
Patch Surfaces
If you select a patch surface, the Patch Open/Close dialogue box is displayed.
In U, V opens or closes the patch along the u or v direction.
NURBS Surfaces
If you select a NURBS surface, the NURBS Open/Close dialogue box is displayed
Note:
You cannot open or close a trimmed NURBS Surface.
If you wish to do so:
- Delete the trim curves from the surface using Draw->Delete Trim Curves. If you have deleted the original curve used to trim, you may extract the trim curve before deleting (using Draw->Extract) and reuse it for projection.
- Open or close the NURBS surface using Draw->Open/Close.
- Trim the NURBS surface again, using Draw->Trim NURBS Surface.
Open/Close
These options allow you to choose the method by which a surface is opened or closed in either the u or v direction.
Note:
Once you close a surface using a given method, the surface can be reopened, but it is not advisable to change the closure method because the results may be unpredictable.
For example, if you close a surface with the Normal selection, you can reopen it, but you shouldn't change to the Linear or Preserve Shape because the shape of the original surface will probably change unpredictably.
- Normal: This is the default value. It opens or closes the NURBS surface by interpolating between all control points and as a result, the shape of the surface as a whole is affected.
- Preserve Shape opens or closes the surface while preserving the shape of the original segments you drew. When this option is selected, you can change the values for the Start, Close, and End Extent sliders to modify the shape of the closing segment without altering the shape of the original segments.
- Linear closes the surface by inserting a new straight line segment between the start and end points. New control points are added in the close segment.
Direction
Toggle U, V, U and V: Opens or closes the surface along the selected direction.
Extent
The Extent sliders allow you to modify the shape of the closing segment in different ways and view the results immediately, without modifying the shape of the original surface. They are only accessible in a Close operation when the Preserve Shape option is selected.
- Start Extent stretches the closing segment along the tangent of the surface starting points (in the given direction).
- Close Extent stretches the closing segment along the tangent of the surface at both the start and end points (in the given direction).
- End Extent stretches the closing segment along the tangent of the surface end points (in the given direction).
NURBS Curves
When you close a NURBS curve, it remembers your selection for closing it. If you reopen the curve, it is reopened the same way it was closed.
If you select a NURBS curve and choose the Draw->Open/Close command, the NURBS Open/Close dialogue box is displayed.
Open/Close
These options allow you to choose the method by which a curve is opened or closed. These options are the same as for a NURBS surface (on NURBS Surfaces) except that they apply to a NURBS curve.
Note:
Once you close a curve using a given method, the curve can be reopened, but it is not advisable to change the closure method because the results may be unpredictable.
- For example, if you close a curve with the Normal selection, you can reopen it, but you shouldn't change to the Linear or Preserve Shape because the shape of the original curve will probably change unpredictably.
Extent
These options are the same as for a NURBS surface (on NURBS Surfaces) except that they apply to a NURBS curves.
Last updated 08-apr-1998