Constructors. The first uses a default cylinder aligned with the Y axis with radius 1.0; the cylinder is supplied in the second. The
orientToEye parameter determines whether the sheet is perpendicular to the eye,
or perpendicular to the cylinder's Z axis. Setting that parameter to TRUE (the default) specifies that the plane be perpendicular to the eye, which is most often the desired behavior.
The default view
volume is undefined, and the working space is identity.