[vtkusers] Stream lines from custom data

[Sebastian Gatzka]

I had the same problem.

You will have to use the vtkCellDataToPointData filter first!
Input to the filter should be your structured grid.

And then you can use the output from this filter as input to the stream
line.

-----Ursprüngliche Nachricht-----
Von: vtkusers-bounces at vtk.org [mailto:vtkusers-bounces at vtk.org] Im Auftrag
von Gomez, Alberto
Gesendet: Mittwoch, 14. April 2010 16:05
Cc: vtkusers
Betreff: [vtkusers] Stream lines from custom data

Hi all,

I have been looking for a way to represent a vector field with stream 
lines, but I have not found a solution so far. My case differs from the 
example in http://www.itk.org/Wiki/VTK/Examples/StreamLines in two things:

I would like to use vtkStreamTracer as vtkStreamLine may be deprecated soon.
I am using custom data and not reading from a file.

So I have my points in the variable positions[][] ( size n x 3) and my 
vectors in the variable directions[][] (size n x 3 also).

I have tried  both StreamTracer and StreamLines but all I see is a black 
background. When using vtkStreamLines I get the error :

Debug: In /data/workspace/vtk-5.4.2/src/Filtering/vtkAlgorithm.h, line 150
vtkStreamLine (0x22a0880): vtkStreamLine (0x22a0880): setting 
AbortExecute to 0

Debug: In /data/workspace/vtk-5.4.2/src/Graphics/vtkStreamer.cxx, line 475
vtkStreamLine (0x22a0880): Generating streamers

ERROR: In /data/workspace/vtk-5.4.2/src/Graphics/vtkStreamer.cxx, line 488
vtkStreamLine (0x22a0880): No vector data defined!

But I actually define the vectors, so I do not know what I am doing wrong.

This is my source code (an extract of it)


vtkSmartPointer<vtkPoints> pts = vtkSmartPointer<vtkPoints>::New();

    vtkSmartPointer<vtkDoubleArray> vecArr =    
vtkSmartPointer<vtkDoubleArray>::New();
    vecArr->SetNumberOfComponents(3);

    for (int i = 0; i < n; i++) {
        pts->InsertNextPoint(positions[i][0], positions[i][1], 
positions[i][2]);
        vecArr->InsertNextTuple3(directions[i][0] , directions[i][1] , 
directions[i][2] );
    }

// Generate the vector field
    vtkSmartPointer<vtkStructuredGrid> sGrid = 
vtkSmartPointer<vtkStructuredGrid>::New();
    sGrid->GetCellData()->SetVectors(vecArr);
    sGrid->SetPoints(pts);
//Generate start points
    vtkSmartPointer<vtkPointSource> seeds = 
vtkSmartPointer<vtkPointSource>::New();
        seeds->SetRadius(20.0);
        seeds->SetCenter(positions[0][0], positions[0][1], positions[0][2]);
        seeds->SetNumberOfPoints(100);

//vtkSmartPointer<vtkStreamTracer> streamer = 
vtkSmartPointer<vtkStreamTracer>::New();
    vtkSmartPointer<vtkStreamLine> streamer = 
vtkSmartPointer<vtkStreamLine>::New();

        streamer->SetInput(sGrid);
        streamer->SetSource(seeds->GetOutput());
  streamer->SetIntegrationDirection(0);
 streamer->DebugOn();
            streamer->Update();
    vtkSmartPointer<vtkPolyDataMapper> gMapper = vtkSmartPointer<
            vtkPolyDataMapper>::New();
    gMapper->SetInputConnection(streamer->GetOutputPort());
...


Many thanks!!!!

-- 

Alberto Gómez

/Division of Imaging Sciences
The Rayne Institute
4th Floor, Lambeth Wing
St Thomas' Hospital
London SE1 7EH /

phone: +44 (0) 20 718 88364
email: alberto.gomez at kcl.ac.uk <mailto:alberto.gomez at kcl.ac.uk>

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