GPELA2 - Elliptical Arc 2

Purpose

Use GPELA2 to insert an Elliptical Arc 2 structure element into the open structure following the element pointer or to replace the element pointed at by the element pointer with an Elliptical Arc 2 structure element depending on the current edit mode.

The graPHIGS API draws the portion of an ellipse (defined by the major and minor axes) specified by the start and end (startv and endv respectively) parameters.

The major and minor axis (refv1 and refv2 respectively) parameters define a parallelogram that circumscribes the ellipse and is anchored at the center of the ellipse. Two sides are parallel to the major axis. The other two sides are parallel to the minor axis. The major and minor axes extend from the center of the ellipse to midpoints of sides of the parallelogram. The ellipse is tangent to the sides of the parallelogram at their midpoints.

The elliptical arc is defined parametrically as the image of an arc of the unit circle in a two-dimensional parameter space. The major and minor axes are images of unit parameter vectors in the x and y directions respectively. The graPHIGS API draws elliptical drawn from the starting angle to the end angle through increasing parameter values.

Polyline attributes are applied to this primitive.

GPELA2 is identified as GDP 1009.

Note:

Not all GDPs are supported on all workstations. Use the Inquire List of Generalized Drawing Primitives (GPQGD) subroutine to determine the GDPs supported by an opened workstation. See also the workstation description in The graPHIGS Programming Interface: Technical Reference

Parameters