[vtkusers] interpolating using RungaKutta4

[Berk Geveci]

What values does ComputeNextStep() return? The ComputeNextStep()
is a very simple and short function. You can easily figure out
what is going wrong by putting a break point in it and following
the execution. I could tell you more if I had access to the datasets.

-Berk


On Thu, 2004-08-26 at 11:12, tom fogal wrote:
> I'm trying to interpolate a point using RungaKutta4 and I'm not getting
> the results I would have expected.
> 
>    float seed[2][3];
>    float delT = 0.5;
>    float unused;
>    vtkInterpolateDataSetAttributes *IntDataSetAttr;
>    vtkInterpolatedVelocityField    *IntVelField;
>    vtkRungaKutta4                  *RG4;
>    MyCustomReaderObject            *src[2];
> 
>    ... initialize data ...
> 
>    IntDataSetAttr->AddInput(src[0]->GetOutput());
>    IntDataSetAttr->AddInput(src[1]->GetOutput());
>    IntDataSetAttr->SetT(0.5);
>    IntDataSetAttr->Update();
>    IntVelField->AddDataSet(IntDataSetAttr->GetOutput());
>    IntVelField->SelectVectors("V");
>    RG4->SetFunctionSet(IntVelField);
> 
>    seed[0][0] = 0.1;
>    seed[0][1] = 0.2;
>    seed[0][2] = 0.3;
>    seed[1][0] = 0.5;
>    seed[1][1] = 0.6;
>    seed[1][2] = 0.7;
>    // seed[1] is for return value
>    RG4->ComputeNextStep(seed[0], seed[1], 0.0, delT, unused, unused);
> 
>    std::cout << "interpolated points (start \t finish):\n"
>              << "\t x: " << seed[0][0] << '\t' << seed[1][0] << '\n'
>              << "\t y: " << seed[0][1] << '\t' << seed[1][1] << '\n'
>              << "\t z: " << seed[0][2] << '\t' << seed[1][2] << '\n';
> 
> I used to not set seed[1] but I was curious to see if it would use
> those values. ComputeNextStep seems to only copy seed[0] to seed[1].
> Any ideas what I'm doing wrong here? How is one supposed to use
> RungaKutta4 ?
> 
> TIA,
> 
> -tom
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-- 
Berk Geveci <berklist at nycap.rr.com>