Constructors. The first uses a default sphere centered at the origin with radius 1.0; the sphere is supplied in the second. The position of the plane which slices the sphere into a section is specified
as a fraction of the sphere radius with the parameter
edgeTol. A tolerance value of 1.0 positions the plane down the center of the sphere. A tolerance value of 0.5 defines the longitudinal plane halfway between
the center and the outside edge of the sphere. The default value is .9, so that almost half the sphere is in front of the plane. The
orientToEye parameter determines whether the plane is perpendicular to the eye,
or perpendicular to the sphere'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.