CenterStage Object Class:  SurfaceVectors
Subclass of:  Arrows
Requires reference to a Surface object

The SurfaceVectors class lets you generate different types of vectors 
associated with a surface.  Arrows will be generated at the corners of each 
subdivision of the surface domain (determined by the Domain directive).  
The types of arrows are listed in the VECTOR menu, and you may select as 
many as you want.  After selecting the vectors, press UPDATE to compute 
them.  The VECTOR/UNIT menu means that the vectors will be normalized to 
unit length.

The types of vetors are:

	Normal		The surface normal vector
        Tangent U       The partial derivative vector with respect to the
                          surface's first parameter
        Tangent V       The partial derivative vector with respect to the
                          surface's second parameter

The SurfaceVectors class supports all the standard directives, together
with the ArrowHead, ArrowScale and ArrowMaxLen directives of the Arrow
class, and the Domain directive of the SurfaceFromSurface class.