[vtkusers] Get points within specific range

[David Doria]

On Mon, Feb 23, 2015 at 5:09 AM, madz <madaramh at gmail.com> wrote:

> What method can I use to get the points between a specific X range with
> static Y and Z values?
>
> eg - Get point ids between the ranges of,
>     p1 - 0.1 ,0.23, 0.78
>     p2 - 123.0 ,0.23, 0.78
>
> Any help would be greatly appreciated.
>

One way to do this would be to select points inside a cube that is huge
(much much larger than your data) in two dimensions and with the bounds on
your X range as the third dimension. Then you could use something like the
following (though it is currently returning 0 points extracted, so you'll
have to figure out what is wrong):

#include <vtkCubeSource.h>
#include <vtkExtractSelectedFrustum.h>
#include <vtkPlanes.h>
#include <vtkPointSource.h>
#include <vtkPolyData.h>
#include <vtkSmartPointer.h>

int main(int, char *[])
{
  // Define your selection region
  vtkSmartPointer<vtkCubeSource> cubeSource =
      vtkSmartPointer<vtkCubeSource>::New();
  cubeSource->SetCenter(0,0,0);
  cubeSource->SetXLength(1);
  cubeSource->SetYLength(1);
  cubeSource->SetZLength(1);
  cubeSource->Update();

  double bounds[6];
  cubeSource->GetOutput()->GetBounds(bounds);

  vtkSmartPointer<vtkPlanes> frustum =
    vtkSmartPointer<vtkPlanes>::New();
  frustum->SetBounds(bounds);

  // Generate some points
  vtkSmartPointer<vtkPointSource> pointSource =
      vtkSmartPointer<vtkPointSource>::New();
  pointSource->SetNumberOfPoints(500);
  pointSource->SetCenter(0,0,0);
  pointSource->SetRadius(5);
  pointSource->Update();

  std::cout << "There are " <<
pointSource->GetOutput()->GetNumberOfPoints() << " input points." <<
std::endl;

  // Extract the points within the frustum
  vtkSmartPointer<vtkExtractSelectedFrustum> extractSelectedFrustum =
      vtkSmartPointer<vtkExtractSelectedFrustum>::New();
  extractSelectedFrustum->SetFrustum(frustum);
  extractSelectedFrustum->SetInputData(pointSource->GetOutput());
  extractSelectedFrustum->Update();

  std::cout << "There are " << vtkDataSet::SafeDownCast
(extractSelectedFrustum->GetOutput())->GetNumberOfPoints() << " output
points." << std::endl;

  return EXIT_SUCCESS;
}
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