Python VTK：奇怪的行为vtkContourFilter

对于我的项目，我必须在三维空间中显示一维路径。为此，我使用vtkContourFilter和以下代码：

import vtk

class Maze(object):
    """Representation of maze"""

    def __init__(self, filename):
        # read source data
        self.reader = vtk.vtkStructuredPointsReader()
        self.reader.SetFileName(filename)
        self.reader.Update()

        # map source data to object
        self.mapper = vtk.vtkDataSetMapper()
        self.mapper.SetInputConnection(self.reader.GetOutputPort())

        # create actor for object
        self.actor = vtk.vtkActor()
        self.actor.SetMapper(self.mapper)

class Path(object):
    """Representation of a path through the maze"""

    def __init__(self):
        # Point list
        self.points = []

        # data source
        self.vtk_points = vtk.vtkImageData()
        self.vtk_points.SetDimensions(100,100,100)
        info = self.vtk_points.GetInformation()
        self.vtk_points.SetPointDataActiveScalarInfo(info,vtk.VTK_UNSIGNED_SHORT,1)
        self.vtk_points.AllocateScalars()
        self.vtk_points.SetSpacing(1,1,1)  
        self.vtk_points.SetOrigin(0,0,0)

        # fill in data with 3D cube
        for x in xrange(1,10):
            for y in xrange(1,10):
                for z in xrange(1,10):
                    self.vtk_points.SetScalarComponentFromFloat(x,y,z,0,1)
        # fill in data with 1D line
        for x in xrange(1,100):
            self.vtk_points.SetScalarComponentFromFloat(x,x,x,0,1)

        # add filter
        self.contour_filter = vtk.vtkContourFilter()
        self.contour_filter.SetInput( self.vtk_points )
        self.contour_filter.SetValue( 10, 1 )

        # map source data to object
        self.mapper = vtk.vtkPolyDataMapper()
        self.mapper.SetInput( self.contour_filter.GetOutput() )

        # create actor for object
        self.actor = vtk.vtkActor()
        self.actor.SetMapper( self.mapper )


def create_renderer():
    renderer = vtk.vtkRenderer()
    renderer.SetBackground([0.5, 0.5, 0.5])
    return renderer

def create_window():
    window = vtk.vtkRenderWindow()
    window.SetSize(1024, 768)
    return window

def create_interactor():
    interactor = vtk.vtkRenderWindowInteractor()
    return interactor

def main():
    # Create/Init data sources (maze, mouse, text, ...)
    path = Path()
    maze = Maze("maze_2_values.vtk")

    # Request their actors
    path_actor = path.actor

    # Create renderer & add actors
    renderer = create_renderer()
    renderer.AddActor(path_actor)

    # Create window & add renderer
    window = create_window()
    window.AddRenderer(renderer)

    # Create interactor, add window & add observers
    interactor = vtk.vtkRenderWindowInteractor()
    interactor.SetRenderWindow(window)

    # Start renderer & interactor
    window.Render()
    interactor.Initialize()
    interactor.Start()

if __name__ == "__main__":
    main()

这将生成我想要的行为：coutourfilter渲染立方体和对角线。但是，当我只交换2行代码时

path = Path()
maze = Maze("maze_2_values.vtk")

到

渲染结果完全不同：只显示立方体（而不是对角线），其颜色现在为蓝色，而不是读取。这怎么可能？这两个类彼此不依赖，也不共享任何资源。所以我不知道交换订单怎么会有这么奇怪的影响

maze = Maze("maze_2_values.vtk")
path = Path()