Extract

The Draw->Extract command in the Model module allows you to extract a curve from a face or a surface. The extracted curve is the same type as that used to create the object from which it is extracted.

This command is useful if you wish to copy a curve identical to one on an existing surface. Having extracted this curve, you can extrude, revolve, or skin it, or perform any operation that can be done with a curve.

You can also use relational modelling concepts on the curve extracted using this command and thus on any objects created from that curve.

To use relation modelling, make sure that the Preferences->Create Modelling Relation command is activated first. Relational modelling is discussed in the Modelling User's Guide.

If you are working with a face or patch, you can only extract curves as displayed. The extraction is executed immediately and you must reselect the surface if you want to extract another curve.

If you are working with a NURBS surface, you can extract a curve anywhere on the NURBS, not just where the curve lines are displayed. The shape of the resulting extracted is affected by two parameters in the NURBS Curve Setup dialogue box: Error Tolerance and Angle of Discontinuity, described in Data Fitting.

Procedure

1. Select a face or surface object.
2. Choose the Draw->Extract command.
3. If you are working with a patch surface:

• Pick the curve on the to extract on u or v. The extracted curve is now selected and the patch object is deselected.
• Right-click to end the mode.
• To pick another curve, reselect the patch and repeat the operation.

4. If you are working with a NURBS surface, when you pick a curve it flashes magenta and the NURBS Extract Curve dialogue is displayed.
5. Select any Location in U or V to extract a curve. Select any projected or trim curves from the list.

• Click Extract. You can keep extracting without exiting the dialogue box.
• Click Exit to exit the dialogue box when you're done.
  

Parameters

In this dialogue box, you can choose whether to extract one or more curves anywhere on the NURBS surface. For a trimmed NURBS surface, you can also extract one or more of the trim curves.

The dialogue box allows you repeat the operation before exiting it.

Surface Curves

If this option is selected, you can use the Location slider to choose a location anywhere on the surface (in u or v) from which to extract the curve. As you move the slider, the magenta line indicates the current location on the selected object.

Trim and Projected Curves

If this option is selected, you can view a list of curves which have been projected onto the surface (either by projection or trimming methods), and select any of them for extraction.

Extract

Extracts the selected curve. Repeat the steps of selecting and extracting as many times as necessary.

Exit

Closes the dialogue box.

Last updated 08-apr-1998