在Windows上添加到vtkImageViewer时，vtkActor2D不可见

Question

我正在使用vtkImageViewer类来显示3D体积中的不同平面。然后我喜欢覆盖垂直和水平线以标记当前鼠标位置。 我使用以下代码向查看器添加vtkActor2D：

    imageViewer = vtk.vtkImageViewer()        
    ...
    line = vtk.vtkLineSource()
    line.SetResolution(20)
    mapper = vtk.vtkPolyDataMapper2D()
    mapper.SetInputConnection(line.GetOutputPort())
    actor = vtk.vtkActor2D()
    actor.SetMapper(mapper)
    imageViewer.GetRenderer().AddActor2D(actor)
    ...
    line.SetPoint1(x,0.0,0.0)
    line.SetPoint2(x,y,0.0)
    actor.GetProperty().SetColor(color)
    actor.GetProperty().SetOpacity(0.75)
    ...
    imageViewer.Render()

在Mac OS X上它按预期工作，但是当我尝试使用我的Windows机器时，该线路根本没有显示。

更新： 如果我改为vtkActor而不是在imageViewer后面渲染actor，我该如何将vtkActor带到前台？

    imageViewer = vtk.vtkImageViewer()        
    ...
    line = vtk.vtkLineSource()
    line.SetResolution(20)
    mapper = vtk.vtkPolyDataMapper()
    mapper.SetInputConnection(line.GetOutputPort())
    actor = vtk.vtkActor()
    actor.SetMapper(mapper)
    imageViewer.GetRenderer().AddActor(actor)
    ...
    line.SetPoint1(x,0.0,0.0)
    line.SetPoint2(x,y,0.0)
    actor.GetProperty().SetColor(color)
    actor.GetProperty().SetOpacity(0.75)
    ...
    imageViewer.Render()