[Insight-users] itk::SimplexMesh and flipped Normals

[Leila Baghdadi]

Sebastian,

That is definitely odd, infact I am really surprised to hear that since I have been that class in numerous programs and never found this problem,

I will check this and get back to you soon however,
if the normals are as you say flipped deforming the mesh will create shrinkage instead of expansion,

Leila


----- Original Message -----
From: "Kiunke, Sebastian" <Sebastian.Kiunke at medizin.uni-leipzig.de>
Sent: Mon, 5/21/2012 11:51am
To: insight-users at itk.org
Subject: [Insight-users] itk::SimplexMesh and flipped Normals


Hello,

im currently working on a simplex mesh deformable model.
My Problem is, that the normals calculated with the "ComputeNormal" function and also if i calculate them in a standard fashion some normals are flipped.
Thats a problem because the internal forces tend to destruct the mesh and the lighting is not correct.

To get the SimplexMesh i use vtkMarchingCubes to extract a vtkPolyData from a binary image.
I convert the vtkPolyData to itk::Mesh and then to an itk::SimplexMesh via the known itk classes.

Weird is that the lighting as vtkPolyData is correct.


In the itk documentation of itk::TriangleMeshToSimplexMeshFilter is written that "Finally the neighbors of the points are reordered counter-clockwise for geometry computation.".
If i do the computation of the normal in a consistent way, shouldn't be correct, and ALL normals point in- or outwards?

I would be very very thankfull for help.


Greetings,
Sebastian
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