[vtkusers] Visualize cell normal vector of polydata

[woshizyc at gmail.com]

Hi, experts,

I want to visualize the normal vectors of a polydata to be centered in the center of each triangle.
I tried to do this for a sphere generated from vtkSphereSource.

I used the following python codes to calculate the normal vectors of the sphere:
sphere = vtk.vtkSphereSource()
sphere.SetCenter(0, 0, 0)
sphere.SetRadius(5.0)
arrow = vtk.vtkArrowSource()
arrow.Update()

normals = vtk.vtkPolyDataNormals()
normals.SetInputConnection(sphere.GetOutputPort())

normals.ComputePointNormalsOff()
normals.ComputeCellNormalsOn()
normals.SplittingOff()
normals.FlipNormalsOff()
normals.ConsistencyOn()
normals.AutoOrientNormalsOn()
normals.Update()

However, it seemed that I did not get the correct normal vectors of each triangle, as you can see in the attached figure. 
In addition, I also do not know how to move the vectors to the center of each triangle.

Could any experts give me some clue for solving this problem.

Are there any example for doing this?

Thanks in advance.

Best,

Yuanchao




woshizyc at gmail.com
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