[vtkusers] Streamlines in an Unstructured Grid

[Erik Anderson]

Hi all,
    I've been having some problems getting streamlines to 
work for me with an unstructured grid.  The Unstructured 
grid has points (x,y,z) and velocities contained in a 
vtkFloatArray named "velocity" per point.  The general 
pipeline I'm trying to use is as follows:

vtkUnstructuredGridReader reader
vtkAssignAttribute a
    a.SetInput(reader.GetOutput())
    a.Assign("velocity", vtkDataSetAttribute::VECTORS, 
vtkDataSetAttribute::VECTORS)
vtkPointSource seeds
    seeds.SetCenter(50, 50, 50)
    seeds.SetRadius(50)
    seeds.SetNumberOfPoints(50)

vtkRungeKutta4 integrate
vtkStreamLine streamer
    streamer.SetIntegrationDirectionToIntegrateBothDirections
    streamer.SetIntegrator(integrate)
    streamer.SetStepLength(0.1)
    streamer.SetIntegrationStepLength(0.1)
    streamer.SpeedScalarsOn()

vtkPolyDataMapper map
    map.SetInput(streamer.GetOutput())

# standard pipeline below forr rendering

I am left with a blank screen (nothing rendered).  When I 
render the seed points, I see them in reasonable places 
within the volume.  Am I do ing something wrong?  Please 
note that the above code is more pseudo-code than a real 
implementation.

Erik