Extrusion

The Surface->Extrusion command in the Model module creates a 3D object out of a curve or a face. You can extrude the selected curve on any axis or along another curve. You can also extrude selected polygons of a polygon mesh object along a curve. Extruded objects can also be bevelled. For an overview of extrusion and examples of the results, see the Extruding a Curve section of the Modelling User's Guide.

You can use relational modelling concepts on most of objects created using this command. Always make sure that the Preferences->Create Modelling Relation command is activated first.

For an overview of relational modelling, see the Relational Modelling section of the Modelling User's Guide.

Procedure

1. Select the curve or face to be extruded.
2. If you wish to extrude along a curve, draw or select the curve that will be the extrusion path.
   
   Note:
   You cannot extrude non-NURBS curves and faces along a NURBS curve. There are no restrictions for extruding NURBS curves and faces along a path of any curve type.
   
3. Choose the Surface->Extrusion command.
   
   The Extrusion dialogue box is displayed.
   
4. Select Polygon, Patch, or NURBS as the resulting object type as well as any associated parameters.
5. Select the desired Axis of Extrusion.
6. Fill in the Step and Depth values.
7. Select Close to close the resulting polygon mesh or surface object.
8. Fill in Bevelling values as required to bevel the extrusion.
9. Click Ok to apply the settings or Cancel to exit the dialogue box.
10. If you selected On Curve, pick the target curve.

The curve remains displayed on the screen after the new extruded object has been created, and can be used again to create more objects. Notice that the original curve and the extruded object are on the same spot.

If you are using relational modelling, as you edit, transform, or scale the generator curves, you will see the object simultaneously move and respond to your changes. The only operations that can be performed independently on the generated object are transformations and inversion of the object's surface normals.

Parameters

Object Type

Not all choices are always available. For example, when extruding polygons on a polygon mesh, the resulting object stays a polygon mesh. When extruding a NURBS, you cannot create a patch object. All curves can create a polygon mesh.

• Polygon: The resulting object is a polygon mesh. You can specify the number of subdivisions between control points.
• Patch: The resulting object is a patch. You can select Linear, Cardinal, or B-Spline type.
• NURBS: The resulting object is a NURBS surface. You can select Linear, Quadratic, or Cubic degree. For more information, see the Degree and Continuity section of the Modelling User's Guide.

Bevelling

To apply bevelling, the curve must be closed and the Close option must be selected in this dialogue box.

• Active activates the bevelling option.
• Radius sets the size of the bevel (reference grid).
• No. bevels sets the number of subdivisions for the bevel.
• Top bevelling, Side bevelling, Bottom bevelling bevels either the top (front), side, or bottom (back) of the object.

Axis of Extrusion

• X, Y, or Z specifies on which of the global axes the extrusion occurs.
• On Curve allows you to specify a target curve as the path of extrusion. When extruding selected polygons of a polygon mesh object, this is the default axis of extrusion, which cannot be modified.

Note:

You cannot extrude non-NURBS curves and faces along a NURBS curve.

Subdivision

Sets the number of subdivisions along the path of extrusion for a curve or face extrusion.

The setting for Subdivision is also applicable in polygon extrusion. That is, when extruding polygons along a curve, you cannot set the number of occurrences, but you can increase the number of steps to achieve a smoother extrusion.

Depth

Sets the total depth of the object along the z-axis, in SOFTIMAGE units.

Step

Sets the resolution of the extruded surface. The higher the value, the smoother the extruded surface will be. This parameter is only available when the resulting object is a Patch or NURBS extrusion.

Close

Applies only if the generator curve is closed.

If you selected the Object Type to be:

• Polygon, the result is a closed polygon mesh object.
• Patch or NURBS, this selection creates a face on the resulting object's top and bottom. The result is a hierarchical object.

Polygon Mode Options

The Curve Placement and Transform options are active only in POL mode, in which case you can extrude a selected polygon along a curve, with or without adding transformations at each step of extrusion along the curve.

Here is an example of a polygon of a polygon mesh extruded along a curve, with a "twist and taper" effect added by specifying a rotation in y (twist) and scale in x and z (taper).

Note:

Relation modelling does not apply when extruding polygons along a curve.

For information and procedures on how to do this, see the Extruding Polygons along Curves section of the Modelling User's Guide. For information on the basic concepts of polygon modelling and an explanation of coordinates and transformations specific to polygons, see the Modelling Selected Polygons section of the Modelling User's Guide.

Last updated 02-apr-1998