Question about visualization

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Question about visualization

Rustem Khabetdinov
Hello,
Is there any way to visualize set of eigenvalues/eigenvectors using vtk? For example, I have this data:
eigenvalues = (-22812140527.70874, -17173061888.51663 ,577143888297.0613)
eigenvectors = (-0.50657551,  0.04671729, -0.860929), (-0.01544831, -0.99886247, -0.04511221),(0.86205719,  0.00955284, -0.50672097)


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Re: Question about visualization

longbowzhang
Basically you try to visualize a 3-by-3 symmetric matrix.
The natural choice is to use an ellipsoid.

Unfortunately, you have negative eigenvalues.
Therefore, the most elegant visualization should be this SuperquadricTensorGlyph.
The code is based on OpenGL, rather than VTK.

Hope this could help or inspire you to some extent.

Longbow
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Re: Question about visualization

Rustem Khabetdinov
As far as I know there is tensorglyph in vtk that allows to visualize superquadrics. I've tried to use it but it gives me incorrect glyph. It always gives me sphere instead of ellipsoid.

2017-07-04 18:44 GMT+03:00 longbowzhang <[hidden email]>:
Basically you try to visualize a 3-by-3 symmetric matrix.
The natural choice is to use an ellipsoid.

Unfortunately, you have *negative* eigenvalues.
Therefore, the most elegant visualization should be this
SuperquadricTensorGlyph
<http://people.cs.uchicago.edu/~glk/sqd/schultzTVCG10SuperquadricTensorGlyphs.pdf>
.
The  code <http://web.ci.uchicago.edu/~schultz/sphinx/superquadrics.html>
is based on OpenGL, rather than VTK.

Hope this could help or inspire you to some extent.

Longbow



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Re: Question about visualization

Dan Lipsa-2
Rustem,
Indeed there is a superquadric source in VTK and ParaView. You can try this source in paraview to see what paramters you need to specify to get the glyph you want.

Dan


On Tue, Jul 11, 2017 at 7:41 AM, Rustem Khabetdinov <[hidden email]> wrote:
As far as I know there is tensorglyph in vtk that allows to visualize superquadrics. I've tried to use it but it gives me incorrect glyph. It always gives me sphere instead of ellipsoid.

2017-07-04 18:44 GMT+03:00 longbowzhang <[hidden email]>:
Basically you try to visualize a 3-by-3 symmetric matrix.
The natural choice is to use an ellipsoid.

Unfortunately, you have *negative* eigenvalues.
Therefore, the most elegant visualization should be this
SuperquadricTensorGlyph
<http://people.cs.uchicago.edu/~glk/sqd/schultzTVCG10SuperquadricTensorGlyphs.pdf>
.
The  code <http://web.ci.uchicago.edu/~schultz/sphinx/superquadrics.html>
is based on OpenGL, rather than VTK.

Hope this could help or inspire you to some extent.

Longbow



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View this message in context: http://vtk.1045678.n5.nabble.com/Question-about-visualization-tp5743875p5743877.html
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