The different types of cross-sections

Axis Aligned

Cross sections are created in the X,Y or Z planes with a regular step size starting from the origin. For example, with a step size of 2.5 cm, the cross section specs are created at -2.5, 0.0, 2.5, 5.0... and so on.

When the Auto Range option is turned on (default), the cross sections are shown over the entire surface. Otherwise, you must explicitly set the range over which the cross sections should be displayed.

Picked Reference

Cross sections are created at the intersection between the geometry and selected section data or construction planes.

NoteSection data can be created from degree 1 NURBS by using the crvToSection plug-in.

Radial

Cross-sections are created based on a driving curve you specify, and the Num Planes option. Points, equally spaced by arc length, are placed on the curve to correspond to the number of sections. A plane is then defined perpendicular to the curve’s tangent at each of these points. The cross-sections are created where the planes intersect the geometry.

The driving curve can be a free curve, a curve-on-surface, or a surface edge or isoparm.

Cross sections can be created by using the Evaluate > Cross Section tool, or by using the Cross Section Control tab in the Modeling control panel.

When using Evaluate > Cross Section , you have to adjust the cross section options every time you select new objects. The cross sections are created as real geometry (NURBS or section data).

With the Cross Section Control tab, you can define groups of cross sections with specific characteristics, apply them to any geometry at any time, and even save them with your model. However, these cross sections are “visual” only (no geometry is created).

NoteVisual cross sections can be transformed into geometry by setting Section Type to NURBS from Visual in the Evaluate > Cross Section option window, and clicking Go.

To create Axis Aligned (X, Y, Z) geometry cross sections

1. Choose Evaluate > Cross Section ❒, to open the option window.
2. Set Section Type to Axis Aligned.
3. Put a check mark in Create Section Data to create section data. Remove the check mark to create NURBS geometry.
4. Select the surface(s) or mesh(es) on which you want to create cross sections. These can also be selected before entering the tool.
5. Press the Go button in the bottom right corner of your view window.

   Purple cross sections appear on the geometry, corresponding to the parameters set in the option window.

6. Change the step size, range or other parameters in the option window if desired, and press Go to update the cross-sections.

   See Evaluate > Cross Section for option details.

To create Picked Reference geometry cross sections

1. Choose Evaluate > Cross Section ❒, to open the option window.
2. Set Section Type to Picked Reference.
3. Put a check mark in Create Section Data to create section data. Remove the check mark to create NURBS geometry.
4. Select the surface(s) or mesh(es) on which you want to create cross sections. These can also be selected before entering the tool.
5. Press the Go button in the bottom right corner of your view window.
6. Select the construction plane(s) and/or section data.
7. Press Go.

   Cross sections appear on the geometry, where it intersects the selected planes/section data.

   NoteIf creating section data cross sections, you can use Curve Edit > Sort Sections to sort out your cross sections into different layers, according to the plane they lie in (X, Y, Z or Other).

To create Radial geometry cross sections

1. Choose Evaluate > Cross Section ❒, to open the option window.
2. Set Section Type to Radial.
3. Put a check mark in Create Section Data to create section data. Remove the check mark to create NURBS geometry.
4. Select the surface(s) or mesh(es) on which you want to create cross sections. These can also be selected before entering the tool.
5. Press the Go button in the bottom right corner of your view window.
6. Select the driving curve(s). More than one curve can be selected if all curves are tangent continuous. Clicking a selected curve deselects it.
   NoteIf Chain Select is turned on, you can select a group of tangent continuous curves all at once.
7. Use the Number of Planes slider in the option window to adjust the number of radial sections. The minimum is 2.

   Small planes, equally spaced by arc length, are displayed on the curve(s), corresponding to the number of sections. The planes are perpendicular to the curve’s tangent at each location.

8. Press Go.

   Cross sections appear on the geometry, where it intersects the planes.

   

To use default cross sections from the Control Panel

1. Pick the surfaces on which you want to display/remove cross sections.
2. In the Cross Section Control options of the Modeling control panel, click the X, Y, or Z preset cross section groups in the list.

   

   NoteYou can select more than one set of cross sections by clicking down while holding the or (Windows) or (Mac) key.
3. Double-click the group’s name to open the option window from where you can change the step size or range.

   See Cross Section Control window for details.

   These cross-sections apply to your entire Alias session.

To create and name a group of visual cross sections

1. Pick the surfaces on which you want to display/remove cross sections.
2. Click the New button in the Cross Section Control options of the Modeling control panel. From the pop-up menu choose Axis Aligned, Picked Reference, or Radial, depending on the type of cross-sections you want to create.
   NoteIf you choose Picked Reference, you need to have some section data or construction plane already selected. If you choose Radial, you will be prompted to select a curve.

   

   The cross section appear in green and the Cross Section Control window opens.

   

3. Delete the default name in the Name text field, and type in a new name. Hit (Windows) or (Mac).

   The new name for the cross section group is displayed in the control panel.

   These user-defined cross-sections can be applied to any surface(s) or meshe(s) and are saved with your model.

4. Check on Store as default if you want the cross section group to become a new default (like the preset X, Y, and Z groups).

   The cross section group appears in gray in the Control Panel. It can then be applied to obejcts in other stages.

   The default group will remain in the Control Panel even after you exit and re-launch Alias. To delete it, you must select it and press the Delete button.

To change the visual cross section settings

You can only modify the settings for Axis Aligned cross sections. In the Cross Section Control window, do the following:

1. Click the X, Y and Z buttons of the axis along which you want the cross sections displayed or removed.
2. Control spacing between cross section lines along the X, Y and Z axes by entering different values in the Step fields. Increase line density by decreasing step values.

To create and change a deviation comb on a visual cross section

1. Click the Curvature ON/OFF checkbox in the Cross Section Control window so that a check mark appears.

   The deviation combs appear in green on the model.

   A Curvature Scale slider and Lock Curvature Scale checkbox appear in the Cross Section Control window.

2. Slide the Curvature Scale slider to scale the length of the curvature combs.
3. Click the Lock Curvature Scale checkbox to prevent any accidental modification of the curvature scale when using the global Comb Scale slider from the Control Panel. (See Control Panel > Curvature ).
   NoteCurvature plots are not available on mesh cross sections.

Tip

• You can control the accuracy of cross sections by setting the Tessellator option in the diagnostic Shading section of the Control Panel. The Accurate setting will produce more accurate cross sections.

To show or hide curvature plots on existing visual cross sections

1. Pick a surface on which you have created cross sections.
2. Click the Curvature ON/OFF checkbox in the Cross Section Control window so that the check mark disappears.