Loft

This task shows how to create a loft feature.

You can generate a loft feature by sweeping one or more planar section curves along a computed or user-defined spine. The feature can be made to respect one or more guide curves. The resulting feature is a closed volume.

Open the Loft1.CATPart document.

Click the Loft icon .

The Loft Definition dialog box appears.

Select the three section curves as shown:

They are highlighted in the geometry area.

The Loft capability assumes that the section curves to be used do not intersect.

Click Apply to preview the loft to be created.

You can note that by default, tangency discontinuity points are coupled:

Several coupling types are available in the Coupling tab:

	`Ratio`: the curves are coupled according to the curvilinear abscissa ratio.
	`Tangency`: the curves are coupled according to their tangency discontinuity points. If they do not have the same number of points, they cannot be coupled using this option.
	`Tangency then curvature`: the curves are coupled according to their curvature discontinuity points. If they do not have the same number of points, they cannot be coupled using this option.
	`Vertices`: the curves are coupled according to their vertices. If they do not have the same number of vertices, they cannot be coupled using this option.

For the purpose of our scenario, you are going to use guide curves. Click the Guide field and select the four joins. The curves to be used must be joined.

They are highlighted in the geometry area.

It is possible to edit the loft reference elements by first selecting a curve in the dialog box list then choosing a button to either:

Remove the selected curve

Replace the selected curve by another curve.

Add another curve.

By default, the application computes a spine, but if you wish to impose a curve as the spine to be used, you just need to click the Spine tab then the Spine field and select the spine of your choice in the geometry.

The Relimitation tab lets you specify the loft relimitation type. You can choose to limit the loft only on the Start section, only on the End section, on both, or on none.

when one or both are checked: the loft is limited to corresponding section

when one or both are when unchecked: the loft is swept along the spine:

if the spine is a user spine, the loft is limited by the spine extremities

if the spine is an automatically computed spine, and no guide is selected: the loft is limited by the start and end sections

if the spine is an automatically computed spine, and guides are selected, the loft is limited by the guides extremities.

Click OK to create the volume.

The feature (identified as Loft.xxx) is added to the specification tree.