非结构化Grid 的网格线

之前我们说过如何查看两个多面体内部的Feature Lines 和外部的 Outline。然而那种方法只适用于Polygonal data，对于Unstructure Grid 并不适用。所以如果我们想要将Unstructured Grid显示出来，那么就需要vtkGeometryFilter这个功能。详情请看下图：

Figure 1 - Mesh visualization pipeline [1]

Putanowicz and Magoules simplified the visualization process of unstructured grids with VTK [1]. The figure shown above clearly displayed how the outline grid can be presented by the VTK reader. 总体的实现过程可查看如下代码：

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def file_open(self, path):
    vtkReader = vtk.vtkUnstructuredGridReader()
    vtkReader.SetFileName(path)
    vtkReader.ReadAllVectorsOn()
    vtkReader.ReadAllScalarsOn()
    vtkReader.Update()

    vtkMapper = vtk.vtkDataSetMapper()
    vtkMapper.SetInputConnection(vtkReader.GetOutputPort())
    actor = vtk.vtkActor()
    actor.SetMapper(vtkMapper)
    actor.GetProperty().SetOpacity(0.9)
    # actor.VisibilityOff()
    self.renderer.AddActor(actor)
    self.renderer.ResetCamera()

    # Create mesh outline via converting unstructured grid to polydata
    # vtkGeometryFilter and vtkExtractEdges used at here
    geometry = vtk.vtkGeometryFilter()
    geometry.SetInputConnection(vtkReader.GetOutputPort())
    poly_mapper = vtk.vtkPolyDataMapper()
    extract = vtk.vtkExtractEdges()
    extract.SetInputConnection(geometry.GetOutputPort())
    poly_mapper.SetInputConnection(extract.GetOutputPort())
    poly_actor = vtk.vtkActor()
    poly_actor.SetMapper(poly_mapper)
    # poly_actor.VisibilityOff()
    self.renderer.AddActor(poly_actor)
    self.renderer.ResetCamera()

根据以上代码，我们就可以将grid outline 显示出来了。

Figure 2 - Plate with meshed grid shown in the Python designed VTK interface

Figure 3 - Plate with meshed grid shown in the Paraview

Reference

[1] Putanowicz, R. and Magoules, F., 2003. Simple visualizations of unstructured grids with VTK.