[vtkusers] How to use vtkRibbonFilter to show a scalar field

[Jean-Do Barnichon]

Hello all,

I want to display a scalar field along a polyline, by making the color 
of each line segment depending on some color scale defined through a 
vtkLookupTable.
Actually, the scalars are known at the polyline nodes, and theses 
scalars are stored in a vtkFloatArray with 1 component.
Well the thing is that I do not get the ribbon in the display, so I 
guess I'm probably doing something wrong.
Note that if I set a given color for the whole actor (obviously it's not 
really what I want, but just for testing) by uncommenting the last line 
of the code snippet given below :
    RibonActor->GetProperty()->SetColor(1.,0.,0.);
it works in the sense that the ribbon is displayed in full red.

Any idea where the problem might come from in my code ?
Thanks,
J-D

Code Snippet
...
   
 /////////////////////////////////////////////////////////////////////////////
    // Create a lookup table that consists of the full hue circle (from 
HSV).
   
 /////////////////////////////////////////////////////////////////////////////
    vtkLookupTable *hueLut = vtkLookupTable::New();
    hueLut->SetHueRange (160./240., 0.);
    hueLut->SetSaturationRange (1, 1);
    hueLut->SetTableRange (minEnergy, maxEnergy);
    hueLut->Build();

    
/////////////////////////////////////////////////////////////////////////////
    // Add the traj in the vertical polyplane
   
 /////////////////////////////////////////////////////////////////////////////
    vtkPoints* trajpoints  = vtkPoints::New(VTK_DOUBLE);
    vtkCellArray* trajpolyline  = vtkCellArray::New();
    // Fill trajpoints and trajpolyline
...

    // Set it to a polydata
    vtkPolyData *trajPD = vtkPolyData::New();
    trajPD->SetPoints(trajpoints);
    trajPD->SetLines(trajpolyline);
    trajPD->Update();

    // Define filter
    vtkRibbonFilter *rf = vtkRibbonFilter::New();
    rf->SetInput(trajPD);
    rf->SetWidth(0.5);
    rf->SetWidthFactor(5);

    // Link mapper
    vtkPolyDataMapper *RibonMapper = vtkPolyDataMapper::New();
    RibonMapper->SetInputConnection(rf->GetOutputPort());
    RibonMapper->SetScalarRange(minEnergy, maxEnergy);
    RibonMapper->SetLookupTable(hueLut);
    RibonMapper->ScalarVisibilityOn();
    RibonMapper->SelectColorArray("EnergyArray");
    RibonMapper->SetScalarModeToUsePointFieldData();
    RibonMapper->SetColorModeToMapScalars();

    // Add actor
    vtkActor *RibonActor = vtkActor::New();
    RibonActor->SetMapper(RibonMapper);
    (RibonActor->GetProperty())->SetInterpolationToFlat();
//    RibonActor->GetProperty()->SetColor(1.,0.,0.);

    // Do usual stuff
...