Fitting Tab

The Prefit button fits a curve to the current points and has the same effect as the prefit icon on the Edit toolbar. If the Centripetal check box is used in conjunction with Prefit, then the resulting spline will be a tighter fit between the data points. This is most useful when fitting angle curves, which may have rapid changes in data. This is equivalent to clicking the icon on the Edit toolbar.

Sort the set of data points

1. Before prefitting, select the type of sort from the dropdown list.

2. Select Sort.

   This only changes the sort temporarily during a prefit.

Change the sort default

• Change the sort method set in the User Parameters dialog under the Sort tab (see User Parameters Dialog - Sort Tab)

Fit a segment of an arc on the current curve

• Through three points, select the 3Pts Radio button then click the Arc button and select the points with the cursor.

Fit an arc through two points with a specified radius

3. Select the 2pts+Rad Radio button.

4. Enter the radius in the Rad edit box and then select Arc.

Replace a knuckle with an arc of known radius

5. Select the Tan+Rad Radio button, and then enter the radius in the Rad edit box.

6. Select Arc.

   The Inc (increment) edit box is used to control the spacing of the points, in degrees, around the arc.

Change the point type of a selected point

7. Select either Ordinary, Knuckle or Tangent as appropriate, and then click the Point Type button.

Assign an angle to a knuckle or tangent point

8. Select Angle ON, enter the angle value in the Angle edit box and click Point Type.

   For a knuckle point, the user has the option of selecting the Upper check box to set the upper angle, else the lower angle is assumed.

9. Use the Angle OFF Radio button to remove an angle assigned to a point.

Figure 1:6. The lower Panel of the Edit Dialog - Fitting Tab.

The user can see the effect that the changes to the current curve have on the intersecting orthogonal curves, using the update facility in the lower panel. As a curve is being modified, the user can at any time force an update. The updated curves are displayed in an appropriate view.

Use the update facility

10. Select the Appropriate Radio button to select the orthogonal curves to be updated which can be section, waterline or buttock.

11. Select Update to make the change.

12. The Local option restricts the changes to the updated curves to 2 spans, the default is 4 spans.

13. Select Accept to keep the changes to the intersecting curves and to reflect these changes in the orthogonal curves to which the current curve belongs.

    If the current curve is a Cline generated by the 3D curve "Project & Fair" algorithm, then the user may only update sections and using Accept will update the intersecting 3D curves.