[vtkusers] vtkLookUpTable negative scalars

[James Labiak]

(vtk 6.0, Java wrapper) When using a vtkLookUpTable to map scalar values 
to hue range, it appears that everything works correctly when the table 
range is entirely positive, but when the table range is entirely 
negative, the graphical output is blank. If this is intended behavior, 
then I would make my own LUT except for mapper.SetLookupTable(hueLut). 
Is this likely my error or a LUT issue?