Cut curves display mode

Cut curves are the intersections between orthogonal planes (constant x, y or z) and the B-Spline surface, forming section, waterline and buttock curves (see Figure 3:122 below). These provide useful visual feedback regarding the shape and fairness of the surface. This display mode is selected using DISPLAY \ PATCH \ INTERSECTION CURVES or .

Figure 3:122. Section, waterline and buttock curves cut from the surface.

Cut curves (which appear in the Patch View tree) are not to be confused with the B-Spline curves (which appear in the Curve View tree). To help avoid confusion, cut curves have different colours to the B-Spline curves of the same orientation. The shape of cut curves cannot be edited directly, rather, their shape changes as the patches that they pass through are edited. This occurs in real time.

Cut curves are added using the Add Cut Curves dialog (see Figure 3:123 below).

Figure 3:123. Add cut curves dialog.

This is launched by selecting PATCH \ ADD SURFACE INTERSECTIONS or . Alternatively, click the Right Mouse button on the Sections, Waterlines or Buttocks root nodes of the Patch View tree, and select the appropriate option (ADD SECTIONS… ) from the popup menu.

The type of cut curves to add is specified in the Intersection plane orientation group. In the Intersection plane positions group, there are three ways of adding cut curves:

• Use Range to add a range of equally spaced curves. The user specifies lower and upper limits in the From and To boxes, plus the spacing in the Inc. box.

• Use Series to add one or more curves at specified positions, separating the position values with commas and/or spaces.

• Use From curve positions to add curves at the same positions as existing B-Spline curves of the same orientation.

Cut curves appear under the Sections, Waterlines and Buttocks nodes of the Patch View tree. Select one or more cut curves by clicking on their name (for multiple selections hold <Ctrl>, contiguous selections hold <Shift>). Clicking the Light Mouse button launches the popup menu used to control the curves. Selecting TOGGLE DISPLAY and TOGGLE CURVATURE respectively toggles the display of the selected curves and their curvature tufts. Selecting DELETE deletes all the selected curves. These operations can be performed for all curves of a particular orientation using the popup menu launched by selecting the appropriate root node (Sections, Waterlines or Buttocks) and clicking the Right Mouse button.

The curvature tuft display (see Figure 3:124 below) is particularly useful for assessing and interactively improving the fairness of the surface. The advice regarding curvature distribution is the same as that given for fairing B-Spline curves (see Curvature Display).

Figure 3:124. Curvature tufts displayed on a cut curve.