Xsection curve height (used to identify the transverse and longitudinal Xsections—see Stretch Form Process Feasibility) is estimated in one of two ways:

The curve height is usually estimated as the difference between the x components of the Xsection properties Rectangle Upper Right and Rectangle Lower Left. The accuracy of this method of estimation can suffer when an Xsection ends at a cutout. In some such cases, this method yields a smaller height than the height of parallel cross-sections that avoid the cutout.

If the Xsection hull is close to being a circular arc, aPriori uses a different, trigonometric method (described below) that provides an accurate estimate. If the Xsection ends at a cutout and the hull is not close to being an arc, aPriori may underestimate the curve height.

The Xsection hull is considered close to being a circular arc if Hull Max Curvature is no more than 20% greater than Hull Average Curvature.

Note that among the cases in which the hull is not close to being an arc are cases in which the Xsection intersects a flange on the part.

With the trigonometric method, the cost model treats the Xsection hull as an arc of a circle whose radius is 1/Hull Avg Curvature, where the length of the arc is Curve Length Extended Aligned. The curve height (h in the diagram below) is calculated as the distance along a radius from the arc to the midpoint of the chord connecting the arc endpoints:

Curve height (h in the diagram) is the difference between the following:

This is x in the diagram. It is the distance from the center of the circle (of which the hull is an arc) to the chord midpoint. The distance depends on the following:

This is the angle in radians subtended by the arc. It is the quotient of the following: