[vtkusers] Visualize cell normal vector of polydata

[woshizyc at gmail.com]

Thanks for your reply and help.

The following is my codes:
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()

mapper = vtk.vtkPolyDataMapper()
if vtk.VTK_MAJOR_VERSION <= 5:
    mapper.SetInput(sphere.GetOutput())
else:
    mapper.SetInputConnection(sphere.GetOutputPort())

glyph=vtk.vtkGlyph3D()

glyph.SetInputData(normals.GetOutput())
glyph.SetSourceData(arrow.GetOutput())
glyph.SetVectorModeToUseNormal()
glyph.SetScaleModeToScaleByVector()
glyph.SetScaleFactor(1)
glyph.OrientOn()
glyph.Update()
print (glyph)

glyph_mapper=vtk.vtkPolyDataMapper()
glyph_mapper.SetInputData(glyph.GetOutput())
glyph_mapper.ImmediateModeRenderingOn()
glyph_actor=vtk.vtkActor()
glyph_actor.SetMapper(glyph_mapper)
glyph_actor.GetProperty().SetColor(1,0.4,1)

actor = vtk.vtkActor()
actor.SetMapper(mapper)



woshizyc at gmail.com
 
From: Cory Quammen
Date: 2017-11-28 22:43
To: woshizyc at gmail.com
CC: vtkusers
Subject: Re: [vtkusers] Visualize cell normal vector of polydata
How did you generate the arrow glyphs? My guess is that the problem is there rather than in the generation of the cell normals, which appears to me to be correct.

Thanks,
Cory

On Tue, Nov 28, 2017 at 8:20 AM, woshizyc at gmail.com <woshizyc at gmail.com> wrote:
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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-- 
Cory Quammen
Staff R&D Engineer
Kitware, Inc.
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