[vtkusers] problem with isosurface and colors

[Julia Faurie]

hi!
i have an isosurface and i want to assign a color to each point of the
isosurface according to his coordinates (the three coordinates are the
red green blue components)
So i used a look up table (in my vtk file i associated scalars value to
each point, and the data is an colors histogram so every point has a
different scalar value)
I get an isosurface with rights colors but there are some blobs on the
surface which have wrong colors and i can't find why...
So if anyone knows what i'm doing wrong or if anyone knows a easier way
to do that...
thanks

my code:

//reader for the isosurface

   vtkStructuredPointsReader *reader =
vtkStructuredPointsReader::New();
     reader->SetFileName(nomfichier);
     reader->SetScalarsName("scalars");
     reader->Update();


//Reader fot the colors (scalars values)

     vtkStructuredPointsReader *coul =
vtkStructuredPointsReader::New();
     coul->SetFileName(nomfichier);
     coul->SetScalarsName("scaltab");
     coul->Update();



//creation of the look up table

     vtkLookupTable *clut=vtkLookupTable::New();
     clut->SetNumberOfColors(hsize*hsize*hsize);
     clut->Build();
     int numerop=0;
     for (int r = 0; r < hsize; ++r)
       for (int g = 0; g < hsize; ++g)
  {
    for (int b = 0; b < hsize; ++b)
      {
        //division to have datas between 0 and 1
        float re=((float)r)/248;
        float gr=((float)g)/248;
        float bl=((float)b)/248;
        clut->SetTableValue(numerop,re,gr,bl,1.0);
        numerop++;
      }
  }


...
and later:

//colors+ datas

    vtkProbeFilter *probe2=vtkProbeFilter::New();
    probe2->SetInput (iso->GetOutput());
    probe2->SetSource (coul->GetOutput());

    vtkCastToConcrete *cast2=vtkCastToConcrete::New();
    cast2->SetInput(probe2->GetOutput());

    //normals
    vtkPolyDataNormals *normals=vtkPolyDataNormals::New();
    normals->SetInput(cast2->GetPolyDataOutput());
    normals->SetFeatureAngle(45);

    //mapper
    isoMap->SetInput(normals->GetOutput());
    isoMap->ScalarVisibilityOn();
    isoMap->SetScalarRange (scalrang[0],scalrang[1]);
    isoMap->SetColorModeToMapScalars();
    isoMap->SetLookupTable(lut);