Re: [vmtk-users] How to improve the computing of centerlines?

[Luca A. <luc...@gm...>]

Hello Haibin,
 the issue is very likely not "near" or "far", but the fact that your distal vessels are very thin compared to the 
surface triangle resolution. This causes the Voronoi diagram to degenerate and the centerline backtracking 
to fail.

The workaround in these cases is to use 
vmtksurfacesubdivision -method loop
prior to centerline computation in order to artificially increase the resolution of the surface.

If the number of triangles becomes very large after subdividing, you can add a decimate step, making it become

vmtksurfacesubdivision -method loop -ifile foo.vtp --pipe vmtksurfacedecimation -reduction 0.5 --pipe vmtkcenterlines ...

Hope this helps.

Luca



On Apr 20, 2013, at 4:22 AM, Haibin Cai wrote:

> Dear vmtkusers,
>    I have a problem of  computing centerlines when I position one soure point and one target point. If the target point is comparative near, it works well. But when I put the target point comparative far, it start from other point. It seems that the branch is not connected. Furthermore, there is three warnings:
> 
> Generic Warning: In C:\Users\orobix\Documents\VMTK\vmtk-build\VTK\Common\vtkMath.cxx, line 553
> Unable to factor linear system
> 
> Warning: In C:\Users\orobix\Documents\VMTK\vmtk-build\VTK\Graphics\vtkDelaunay3D.cxx, line 487
> vtkDelaunay3D (0311A688): 149 degenerate triangles encountered, mesh quality suspect
> 
> Warning: In C:\Users\orobix\Documents\VMTK\vmtk\vtkVmtk\ComputationalGeometry\vtkvmtkSteepestDescentLineTracer.cxx, line 231
> vtkvmtkSteepestDescentLineTracer (09FC28B0): Degenerate descent detected. Target not reached.
> Here is the result
> <1.jpg><2.jpg>
> What does the warning mean? What should I do to let the centerline reach the real target point? 
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