[vtkusers] how to speed up vtkVoxelModeller?

[Marie-Gabrielle Vallet]

 Lars,

It's tricky, but you should try to scale you geometry, such that all
distances are less than one. I found this feature using vtkImplicitModeller
which is said to be very similar to vtkVoxelModeller.

See my message "Performance of vtkImplicitModeller" dated from last week.

I also tested my code using a vtkVoxelModeller instead of an implicit one
and the speed up due to the scaling was also 1/100. vtkImplicitModeller is a
more complex class, but it is a little bit quicker.

Regards.
Marie-Gabrielle

> Dear VTK-Users,

> I am using vtkVoxelModeller (vtk5.0) to voxelise polygonal mesh (e.g.
> surface model made out off some ten-thousands quads). The target
> voxel dimensions are about 90 x 50 x 300 = 1.35e6.

> The problem is, that is very slow. On a WinXP Pentium4, 3.4 GHz
> machine it takes days to get one surface model voxelised.

> How can I possibly speed up vtkVoxelModeller?



> Here comes my code:

> vtkPolyData *polyOrgan = vtkPolyData::New();
> polyOrgan->SetPoints(points); // points are generated before
> points->Delete();
> polyOrgan->SetPolys(polys); // polys are generated before
> polys->Delete();
> vtkCleanPolyData *polyOrganClean = vtkCleanPolyData::New();
> polyOrganClean->SetInput(polyOrgan);// get rid of double definitions
> vtkVoxelModeller *voxelmacher = vtkVoxelModeller::New();
> voxelmacher->SetSampleDimensions(90,50,300);
> voxelmacher->SetModelBounds( /* box just around the polydata */ );
> voxelmacher->SetInput(polyOrganClean->GetOutput());
> vtkDataSetWriter *aWriter = vtkDataSetWriter::New();
> aWriter->SetFileName("afile.vtk");
> aWriter->SetInputConnection(voxelmacher->GetOutputPort());


> A performance check told me the following cpu-time fractions when my
> code running:

> 	36.7%	vtkQuad::EvaluatePosition(double*, double*, int&, double*,
double&, double*)	
> 	19.4%	vtkDataArrayTemplate<double>::GetTuple(int, double*)	
> 	7.1%	vtkPoints::GetPoint(int, double*)	
> 	4.5%	vtkTriangle::ComputeNormal(double*, double*, double*, double*)	
> 	3.5%	vtkQuad::InterpolationFunctions(double*, double*)	
> 	3.4%	vtkQuad::InterpolationDerivs(double*, double*)	


> Thanks in advance for any hints to speed up vtkVoxelModeller!
> Best regards

> Lars
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