# [vtkusers] Uneven interpolation from vtkTupleInterpolator?

Bill Lorensen bill.lorensen at gmail.com
Mon Sep 7 10:51:40 EDT 2015

Add
pointInterpolator->SetInterpolationTypeToLinear();
before
pointInterpolator->SetNumberOfComponents(3);

On Sun, Sep 6, 2015 at 10:32 PM, Mengda Wu <wumengda at gmail.com> wrote:
> Hello,
>
>    I am trying to get an even interpolation between two points. For example,
> the following code:
>
>       vtkSmartPointer<vtkTupleInterpolator> pointInterpolator =
> vtkSmartPointer<vtkTupleInterpolator>::New();
>     pointInterpolator->SetNumberOfComponents(3);
>
>     double coord0[3] = {0.0, 0.0, 0.0};
>     double coord1[3] = {0.0, 0.0, 1.0};
>
>     pointInterpolator->AddTuple(0.0, coord0);
>     pointInterpolator->AddTuple(1.0, coord1);
>
>     double coord[3];
>     double t;
>     for(int i=0; i<=3; i++)
>     {
>         t = i/3.0;
>         pointInterpolator->InterpolateTuple(t, coord);
>         std::cout << t << ": " << coord[0] << ", " << coord[1] << ", " <<
> coord[2] << std::endl;
>     }
>
>     gives me:
>     0: 0, 0, 0
>     0.333333: 0, 0, 0.259259
>     0.666667: 0, 0, 0.740741
>     1: 0, 0, 1
>
>     while I am expecting
>     0: 0, 0, 0
>     0.333333: 0, 0, 0.333333
>     0.666667: 0, 0, 0.666667
>     1: 0, 0, 1
>
>     How should I do this? What if I have more than two points and I need an
> interpolating spline which gives points at even distribution?
>
> Thanks,
> Mengda
>
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