[vtkusers] Error in vtkQuad associated with problem with vtkCellDerivatives

[Richard Strelitz]

I have been having problems with vtkCellDerivatives in that it 
unfailingly returns values of "0" regardless of the actual values
of the data.  I was using it with a unstructured grid from which
I had extracted a layer.  Each cell was thus a vtkQuad.  

 The computation of the derivatives depends on the method
    cell->Derivatives(subid, pcoords, scalars, dim, derivs)
 In the process of executing, on line 678  in vtkQuad, the value
 of the sum[1] is computed as += funcDerivs(3+i)*values[dim*i+j]

**** I am pretty sure that it should be funcDerivs(4+i)  *** 
but, I am also pretty sure that that is not the sole source of my trouble.
Has anyone else had dealings with this??

(Just for the record, I am using the latest donwload, but the vtkQuad.cxx
  module is Version:  $Revision 1.6.3  $  of 2000/02/04 17:03:44 $

Thanks,
  Richard Strelitz,
  SciVis Staff , LANL CCS (nee ACL)