[vtkusers] bizarre spline problem

[Anja Ende]

Hi everyone,

I am having a strange problem when visualizing spline data. When I visualize
it, my spline data does not pass through the second last point in the
control point collection. As I add new points interactively, it keeps
updating the spline but it never passes through the second last position!

I create the spline as follows:

m_parametricSpline = vtkParametricSpline::New();
m_parametricSpline->ClosedOff();

vtkKochanekSpline* xspline = vtkKochanekSpline::New();
vtkKochanekSpline* yspline = vtkKochanekSpline::New();
vtkKochanekSpline* zspline = vtkKochanekSpline::New();

m_parametricSpline->SetXSpline(xspline);
m_parametricSpline->SetYSpline(yspline);
m_parametricSpline->SetZSpline(zspline);

xspline->Delete();
yspline->Delete();
zspline->Delete();

m_splineSource = vtkParametricFunctionSource::New();
m_splineSource->SetUResolution(200);
m_splineSource->SetVResolution(200);
m_controlPoints = vtkPoints::New();

The code to add the points is as follows:
As I add points here, the display is updated and the spline never passes
through the second last point.

void KochanekSpline::PushPoint(float x, float y)
{
            int pos = m_controlPoints->InsertNextPoint(x, y, 0.0);
            if (m_controlPoints->GetNumberOfPoints() > 1)
            {
                m_parametricSpline->SetPoints(0);
                m_parametricSpline->SetPoints(m_controlPoints);
                m_splineSource->SetParametricFunction(m_parametricSpline);
                m_splineSource->Update();
            }
}

Now here comes the strange part... I have code that the user can interact
with the control points and move them around. This is pretty similar to the
code above as follows:

void KochanekSpline::SetPointAtIndex(unsigned index, float x, float y)
{
            if (m_controlPoints->GetNumberOfPoints() > index)
            {
                m_controlPoints->SetPoint(index, x, y, 0.0);
                if (m_controlPoints->GetNumberOfPoints() > 1)
                {
                    m_parametricSpline->SetPoints(0);
                    m_parametricSpline->SetPoints(m_controlPoints);

m_splineSource->SetParametricFunction(m_parametricSpline);
                    m_splineSource->Update();
                }
            }
}

This works as intended! As soon as I click on a point, the spline now passes
through all the control points!!

However, as you can see it is pretty similar to the function above! I have
no idea why this is happening.

Any suggestions and help will be greatly appreciated!

Thanks,
Anja
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