Vector scaling

I have succeeded in producing a 3D vector plot with ViSAD. That is, I
have u,v,w components of velocity defined on an x,y,z grid. The problem
is that the vectors drawn at the grid points are hard to see unless you
really zoom into the plot. Is there a way to explicity set a scaling
vactor for the vector magnitudes to accentuate the vector arrows. Simply
multiplying the component magnitudes by a constant doesn't seem to
change anything. Is there some kind of VisAD-internal normalization or
scaling occuring? Thanks in advance.