[vtkusers] how to compute the length of spline?

[Jorge Perez]

Hello, you can use a vtkParametricFunctionSource to sample the parametric
spline and then add the length of the linear segments. You can see how it
can be done by inspecting the method vtkSplineWidget::GetSummedLength at
source code  vtkSplineWidget.cxx

double vtkSplineWidget::GetSummedLength()
{
  vtkPoints* points =
this->ParametricFunctionSource->GetOutput()->GetPoints();
  int npts = points->GetNumberOfPoints();

  if ( npts < 2 ) { return 0.0; }

  double a[3];
  double b[3];
  double sum = 0.0;
  int i = 0;
  points->GetPoint(i, a);
  int imax = (npts%2 == 0) ? npts-2 : npts-1;

  while ( i < imax )
    {
    points->GetPoint(i+1, b);
    sum += sqrt(vtkMath::Distance2BetweenPoints(a, b));
    i = i + 2;
    points->GetPoint(i, a);
    sum = sum + sqrt(vtkMath::Distance2BetweenPoints(a, b));
    }

  if ( npts%2 == 0 )
    {
    points->GetPoint(i+1, b);
    sum += sqrt(vtkMath::Distance2BetweenPoints(a, b));
    }

  return sum;
}

2014-11-01 5:05 GMT+01:00 just_rookie <925345468 at qq.com>:

> Hi all,
>
> I have used the vtkParametricSpline class to get a spline, and my next step
> is to compute the length of the spline, any help? Thank you in advance!
>
>
>
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