# VTK/Examples/Cxx/PolyData/DecimatePolyline

< VTK‎ | Examples‎ | Cxx
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## Decimate one Polyline

This example shows how to decimate one polyline.

Note that this example requires the git (master branch) version of vtk

## DecimatePolyline.cxx

```#include <vtkDecimatePolylineFilter.h>
#include <vtkMath.h>
#include <vtkPolyData.h>
#include <vtkCellArray.h>
#include <vtkPolyDataMapper.h>
#include <vtkActor.h>
#include <vtkRenderer.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkProperty.h>

int main(int, char *[])
{
const unsigned int numberofpoints = 100;

vtkPolyData* circle = vtkPolyData::New();
vtkPoints*   points = vtkPoints::New();
vtkCellArray* lines = vtkCellArray::New();
vtkIdType* lineIndices = new vtkIdType[numberofpoints+1];

for( unsigned int i = 0; i < numberofpoints; i++ )
{
const double angle = 2.0 * vtkMath::Pi() * static_cast< double >( i ) /
static_cast< double >( numberofpoints );
points->InsertPoint( static_cast< vtkIdType >( i ),
cos( angle ),
sin( angle ),
0. );
lineIndices[i] = static_cast< vtkIdType >( i );
}
lineIndices[numberofpoints] = 0;
lines->InsertNextCell( numberofpoints+1, lineIndices );
delete[] lineIndices;

circle->SetPoints( points );
circle->SetLines( lines );
points->Delete();
lines->Delete();

vtkPolyDataMapper* c_mapper = vtkPolyDataMapper::New();
c_mapper->SetInput( circle );

vtkActor* c_actor = vtkActor::New();
c_actor->SetMapper( c_mapper );

vtkDecimatePolylineFilter* decimate = vtkDecimatePolylineFilter::New();
decimate->SetInput( circle );
decimate->SetTargetReduction( 0.95 );
decimate->Update();

vtkPolyDataMapper* d_mapper = vtkPolyDataMapper::New();
d_mapper->SetInput( decimate->GetOutput() );

vtkActor* d_actor = vtkActor::New();
d_actor->SetMapper( d_mapper );
d_actor->GetProperty()->SetColor( 1., 0. ,0. );

vtkRenderer* ren = vtkRenderer::New();

vtkRenderWindow* renwin = vtkRenderWindow::New();

vtkRenderWindowInteractor* iren = vtkRenderWindowInteractor::New();
iren->SetRenderWindow( renwin );

renwin->Render();

iren->Start();

iren->Delete();
renwin->Delete();
ren->Delete();

d_actor->Delete();
d_mapper->Delete();

c_actor->Delete();
c_mapper->Delete();

decimate->Delete();
circle->Delete();

return EXIT_SUCCESS;
}
```

## CMakeLists.txt

```project( DecimatePolyline )
cmake_minimum_required( VERSION 2.6 )

find_package( VTK REQUIRED )
include( \${VTK_USE_FILE} )