.LP
\fBViewimage\fP displays plots from a Perspective projection, similar to 
the \fBxprism3\fP plotting package.  There are three fields
which are relevant to the perspective: eye distance, alpha, and theta.  
The eye distance controls the distance from the eye to the object;  alpha
determines from what angle on the Y/Z plane your eye is looking at the object,
and theta determines from what angle on the X/Y plane your eye is looking at
the object.  Remember that in our coordinate system, X goes left and right,
Z goes up and down, and Y goes in and out (this setup has Y and Z reversed 
from what is taught in many textbooks). 
.LP
The Perspective subform of \fBviewimage\fP offers several fixed perspective 
views.  These include a front view, a back view, a left view, a right view, 
a top view, and a bottom view.  For your convenience, these may be set with the
mouse, and no thought need be given to the values of alpha and theta;  they
will be updated accordingly. Alternatively, the "eye", "alpha", and "theta" 
float selections may be used to move the elevation data to the desired 
perspective.  
.LP
IMPORTANT: unlike 
\fBxprism3\fP, which uses a set of axes to represent the plot, \fBviewimage\fP
will rotate the entire existing plot as you change these values.  Thus, you 
are advised to use only the 3D or Wireframe plot types while
you change the perspective.  If you use one of the plot types with a more 
complicated algorithm (color mesh, for instance)  you will find the
slow redraw time extremely frustrating.
.IP \(bx
eye: moves the eye closer (as the eye distance decreases) or farther away
(as the eye distance increases).
.IP \(bx
alpha: rotates about the X axis clockwise as alpha increases, counter -
clockwise as alpha decreases.
.IP \(bx
theta: rotates about Z axis clockwise as theta increases, counter -
clockwise as theta decreases.
