Defining the shape of the initial surface

When using the Capping command to create a filling surface, in some particular situations the result you get — when the Generic Shape drop-down list under More Options is set to its default value: Automatic — may differ from the one you expect. By properly selecting the Generic Shape value, you can control such situations obtaining the desired result.

The Generic Shape drop-down list enables you to select the best type of surface for your goals:
 

Automatic the program automatically chooses the best type of filling surface among (portions of) a plane, a cylinder or a sphere.
Flat the surface that will be used is a portion of a plane to be defined using the Reference Plane drop-down list which shows up as soon as you select the Flat option. For details on the plane definition method, see " How to define a plane".
Single curvature the surface will be defined as a cylinder. You can define:
  • The Axis (see "How to define an axis or a line" for details).
  • The radius, by selecting the Radius check box (which shows up as soon as you click on Axis) and typing the value into the adjacent box. The default value is displayed when you select the check box for the first time.
  • The orientation of the surface, by selecting/deselecting the Invert check box, displayed as soon as you click on Axis.
Double curvature the surface will be defined as a sphere. You can define:
  • The center.
  • A Direction (see "How to define an axis or a line" for details) which can be used to define the axis between the poles of the sphere, thus defining the directions of the u and v isoparametric curves of the surface. Using this option, you can control the alignment of the isoparametric curves, avoiding undesired rotations.
  • The radius, by selecting the Radius check box and typing the value into the adjacent box.
  • The orientation of the surface, by selecting/deselecting the Invert check box.
Saddle curvature the surface will be defined as a torus. You can define:
  • The Axis of rotation of the torus (see "How to define an axis or a line" for details) and its Origin.
  • The Inner radius, by selecting the corresponding check box and typing the value into the adjacent box.
  • The Section radius, also in this case by selecting the corresponding check box and typing the value into the adjacent box.
Existing surface the surface that will be used is an existing one to be selected (a specific Surface item is displayed in the selection list). You will also have to select a Projection type suitable for the surface you selected. Final results depend on the chosen projection type and on the corresponding direction. Available projection types are the following:
  • Flat — a common direction of projection is used.



    This method implies selecting the direction of projection, an Axis
     
  • Double curvature — a spherical projection is used.



    This method implies selecting the Point to be used as the center of the sphere.
     
  • Single curvature — a cylindrical projection is used.



    This method implies selecting the Axis(see "How to define an axis or a line" for details).
     
  • Normal — a normal projection is used. The normal to the surface at each point of the surface defines the direction of projection.

 

The following is an example of a typical situation in which the Automatic choice is not appropriate.

1 Suppose you have a set of curves like the ones in the following illustration, to be joined by a surface using the Capping command. After starting the command select all the curves using a window selection.



You might reasonably expect the shape of the resulting surface to be cylindrical. Once the curves have been selected, leave constraints to their default values.

2 Click the preview button ( ) to display a preview. The result you get is really different from the one you expected:
3 To obtain a good result, click on More Options to expand and select Single curvature in the Generic Shape drop-down list. Click on the Axis item in the selection list. The Radius and Invert check boxes show up in the model. Select Invert.
4 Click the preview button ( ) to display a preview. The result you get now is the one you expected:
5 Click or to confirm your selections and modify the shape of the object.



Click to discard your changes.
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