[vtkusers] Question to use the vtkStreamTracer

[Yu Zhou]

Hello,


I have a problem with vtkStreamTracer.


Here is the code:


```

def generate_streamline(source_file, dest_file, axis, resolution=1):
    reader = vtk.vtkXMLImageDataReader()
    reader.SetFileName(source_file)
    reader.GetPointDataArraySelection().DisableArray('density')
    reader.Update()
    extent = reader.GetOutput().GetExtent()
    center = [np.mean(extent[0:2]), np.mean(extent[2:4]), np.mean(extent[4:6])]

    seeds = vtk.vtkPointSource()
    seeds.SetCenter(center)
    seeds.SetRadius(10.5)
    seeds.SetNumberOfPoints(100)
    seeds.Update()

    streamTracer = vtk.vtkStreamTracer()
    streamTracer.SetInterpolatorTypeToDataSetPointLocator()
    streamTracer.SetInputData(reader.GetOutputDataObject(0))
    streamTracer.SetSourceData(seeds.GetOutputDataObject(0))
    streamTracer.SetIntegratorTypeToRungeKutta45()
    streamTracer.SetMaximumPropagation(104)
    streamTracer.SetInitialIntegrationStep(0.2)
    streamTracer.SetMaximumIntegrationStep(0.5)
    streamTracer.SetIntegrationDirectionToBoth()
    streamTracer.SetStartPosition(center)
    streamTracer.SurfaceStreamlinesOn()
    streamTracer.Update()

    print(streamTracer.GetOutputDataObject(0))

```

The output is:
```

vtkPolyData (0x273ece0)
  Debug: Off
  Modified Time: 2638
  Reference Count: 2
  Registered Events: (none)
  Information: 0x2ccb540
  Data Released: False
  Global Release Data: Off
  UpdateTime: 2680
  Field Data:
    Debug: Off
    Modified Time: 2628
    Reference Count: 1
    Registered Events: (none)
    Number Of Arrays: 0
    Number Of Components: 0
    Number Of Tuples: 0
  Number Of Points: 0
  Number Of Cells: 0
  Cell Data:
    Debug: Off
    Modified Time: 2636
    Reference Count: 1
    Registered Events:
      Registered Observers:
        vtkObserver (0x2ccc370)
          Event: 33
          EventName: ModifiedEvent
          Command: 0x2ccb880
          Priority: 0
          Tag: 1
    Number Of Arrays: 0
    Number Of Components: 0
    Number Of Tuples: 0
    Copy Tuple Flags: ( 1 1 1 1 1 0 1 1 )
    Interpolate Flags: ( 1 1 1 1 1 0 0 1 )
    Pass Through Flags: ( 1 1 1 1 1 1 1 1 )
    Scalars: (none)
    Vectors: (none)
    Normals: (none)
    TCoords: (none)
    Tensors: (none)
    GlobalIds: (none)
    PedigreeIds: (none)
    EdgeFlag: (none)
  Point Data:
    Debug: Off
    Modified Time: 2638
    Reference Count: 1
    Registered Events:
      Registered Observers:
        vtkObserver (0x2ccc210)
          Event: 33
          EventName: ModifiedEvent
          Command: 0x2ccb880
          Priority: 0
          Tag: 1
    Number Of Arrays: 0
    Number Of Components: 0
    Number Of Tuples: 0
    Copy Tuple Flags: ( 1 1 1 1 1 0 1 1 )
    Interpolate Flags: ( 1 1 1 1 1 0 0 1 )
    Pass Through Flags: ( 1 1 1 1 1 1 1 1 )
    Scalars: (none)
    Vectors: (none)
    Normals: (none)
    TCoords: (none)
    Tensors: (none)
    GlobalIds: (none)
    PedigreeIds: (none)
    EdgeFlag: (none)
  Bounds:
    Xmin,Xmax: (1, -1)
    Ymin,Ymax: (1, -1)
    Zmin,Zmax: (1, -1)
  Compute Time: 2692
  Number Of Points: 0
  Point Coordinates: 0
  Locator: 0
  Number Of Vertices: 0
  Number Of Lines: 0
  Number Of Polygons: 0
  Number Of Triangle Strips: 0
  Number Of Pieces: 1
  Piece: 0
  Ghost Level: 0
```

And I get an empty vtkPolyData without any streamline in it.

Attached please find the testing dataset.


Please help me.


Thanks,


Joey
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