Select array to show in the View3d

[jbrezmorf]

• add drop down menu to select from all CELL DATA arrays (omit those with underscores)
• get arrays:

  def get_array_names(self, data):
      return [data.GetArrayName(i) for i in range(data.GetNumberOfArrays())]

• modification of UnstructeredGridActor:

  class UnstructuredGridActor(vtk.vtkActor):
  def __init__(self, model):
      super(UnstructuredGridActor, self).__init__()
  
      self.model = model
      #self.model.Update()
      array_idx = 3
      self.scalar_range = self.model.GetOutput().GetPointData().GetArray(array_idx).GetRange()
      print("range:", self.scalar_range)
      self.scalar_range = (max(self.scalar_range[0], 0.01), self.scalar_range[1])
      self.mapper = vtk.vtkDataSetMapper()
      self.mapper.SetInputConnection(self.model.GetOutputPort())
  
      self.mapper.SetScalarMode(vtk.VTK_SCALAR_MODE_USE_POINT_FIELD_DATA)
      self.mapper.SetColorMode(vtk.VTK_COLOR_MODE_MAP_SCALARS)
      self.mapper.SelectColorArray(array_idx)
  
      self.mapper.ScalarVisibilityOn()
      self.mapper.SetScalarRange(self.scalar_range)
  
      lut = vtk.vtkLookupTable()
      lut.SetNumberOfColors(2000)
      lut.SetHueRange(0.667, 0.0)
      lut.Build()
      self.lut = lut
      #lut.SetRampToLinear()
  
      #lut.SetRange(self.scalar_range)
      self.mapper.SetLookupTable(lut)
      self.SetMapper(self.mapper)