[vtkusers] Unsteady Vector Field Integration using vtkTemporalStreamTracer

[Tim Biedert]

Hello,

I’m interested in pathline integration in an unsteady vector field. My idea was to construct a vtkMultiBlockDataSet (each block represents a time step) and use vtkTemporalStreamTracer for the integration.

Problem:  How to set the meta information for the time values correctly?

Here's some code:

// Read velocity time steps   (in this example reduced to 2 time steps)
vtkSmartPointer<vtkStructuredGridReader> velocityReader0 = vtkSmartPointer<vtkStructuredGridReader>::New();
velocityReader0->SetFileName(path0);    // analogous for velocityReader1

// Construct multi block data set
vtkSmartPointer<vtkMultiBlockDataSet> velocityData = vtkSmartPointer<vtkMultiBlockDataSet>::New();
velocityData->SetNumberOfBlocks(2);

velocityData->SetBlock(0, velocityReader0->GetOutput());
velocityData->SetBlock(1, velocityReader1->GetOutput());

// Construct temporal stream tracer
vtkSmartPointer<vtkTemporalStreamTracer> tracer = vtkSmartPointer<vtkTemporalStreamTracer>::New();
tracer->SetInputData(velocityData);
tracer->SetSourceConnection(points->GetOutputPort());    // some points where the integration should start

double timeSteps[] = {0.0, 1.0};
tracer->GetInputInformation()->Set(vtkStreamingDemandDrivenPipeline::TIME_STEPS(), timeSteps, 2);


Using the above code I get a runtime error stating “vtkTemporalStreamTracer: No time step info”.
The vtkTemporalStreamTracer.cxx source code suggests I have to set the vtkDataObject::DATA_TIME_STEP information.

By trial and error, I got the error gone by for example:

tracer->GetInputInformation()->Set(vtkDataObject::DATA_TIME_STEP(), 0.0);

However, I don’t understand why the vtkTemporalStreamTracer wants to read a single time step value from the input data (which is a multi block data set).  Besides that the tracer should already know all time values from the vtkStreamingDemandDrivenPipeline::TIME_STEPS() information key, it does not make sense for me why I should assign a single time step to the multi block container, instead of assigning each block data the respective time value.

Of course, the application still crashes with runtime error "vtkTemporalStreamTracer: InitializeInterpolator failed”.


Thank you very much!

Best,
Tim






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