A Plot3D is a specialised form of Plot that provides facilities
for producing 3D graphical output. If a null Object pointer
(AST__NULL) is given, a default 3-dimensional Frame will be used
to describe the physical coordinate system. Labels, etc. may
then be attached to this by setting the appropriate Frame
attributes (e.g. Label(axis)) for the Plot. The first triple of
values should give the coordinates of the bottom left corner of
the plotting volume and the second triple should give the
coordinates of the top right corner. The coordinate on the
horizontal axis should be given first in each pair. Note that
the order in which these points are given is important because
it defines up, down, left and right for subsequent graphical
operations. AST A Library for Handling World Coordinate Systems
in Astronomy