2-3. actors

streamer
seeds = vtkPointSource()
seeds.SetRadius (0.8)
seeds.SetCenter (0.0, 0.0, 0.0)
seeds.SetNumberOfPoints (50)
streamers = vtkStreamLine ()
streamers.SetInput (fData)
streamers.SetSource (seeds.GetOutput ())
streamers.SetMaximumPropagationTime (2.0 / scalarmax)
streamers.SetStepLength (5.0e-2 / scalarmax)
streamers.Update ()
streamersMapper = vtkPolyDataMapper ()
streamersMapper.SetInput (streamers.GetOutput())
streamersMapper.SetLookupTable (lut)
streamersMapper.SetScalarRange (scalarmin, scalarmax)
streamersActor = vtkActor()
streamersActor.SetMapper (streamersMapper)

spherical vessel
sphereV = vtkSphereSource()
sphereV.SetRadius (1.0)
sphereV.SetCenter (0.0, 0.0, 0.0)
sphereVMapper = vtkPolyDataMapper()
sphereVMapper.ScalarVisibilityOff()
sphereVMapper.SetInput (sphereV.GetOutput ())
sphereVActor = vtkLODActor ()
sphereVActor.SetMapper (sphereVMapper)
sphereVProp = sphereVActor.GetProperty ()
sphereVProp.SetOpacity (.1)
sphereVProp.SetColor (0., 0., 0.5)