Removing Data Points

Removing data points is often the most effective way of improving the fairness of a curve. Excessive data points often lead to unwanted undulations in the curve, particularly if they are close together. Also, the effort required for editing is reduced if there are fewer data points to deal with, and the design as a whole becomes easier to manage. 'Thinning out' the data points defining a curve is thus a good first step in the process of manipulation and fairing.

Often, quite a large proportion of the data points defining a curve can be removed, to produce a substantially improved curvature distribution without straying significantly from the original point positions.

When attempting to thin out data points in this way it is useful to see the effect of removing certain points before permanently deleting them. This is done by unchecking cells in the Active column of the Data Points grid. Deactivated data points do not contribute to the shape of a curve, but remain visible (and greyed) in the graphics views for visual comparison purposes.

In the example below, the set of active data points have been reduced from 38 to 10. The curvature distribution is much improved, though the curve remains perceptibly very close to all of the original data points (for clarity, the active data points are shown highlighted).

Figure 3:53. Curve points prior and after thinning.

Once spurious data points have been identified, there are two ways in which they can be permanently deleted:

• Graphically select one or more data points and click <Delete>.

• Select one or more rows in the Data Points grid. Whole rows are selected by clicking the Left Mouse button on the row header (left-most column). Multiple rows can be selected by holding <Ctrl> and contiguous groups of rows by holding <Shift>. With the cursor over one of the selected row headers, click the Right Mouse button and select REMOVE DATAPOINT from the popup menu.

Figure 3:54. Using the popup menu to remove data points.

Attempts to remove data points fail if the number remaining for a particular curve would be less than 2.