# Difference between revisions of "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 (as of 8/5/2010).

## 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>

#include <vtkSmartPointer.h>

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

vtkPolyData* circle = vtkPolyData::New();
vtkSmartPointer<vtkPoints> points = vtkSmartPointer<vtkPoints>::New();
vtkSmartPointer<vtkCellArray> lines = vtkSmartPointer<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 );

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

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

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

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

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

vtkSmartPointer<vtkRenderer> ren =
vtkSmartPointer<vtkRenderer>::New();
ren->AddActor( c_actor );
ren->AddActor( d_actor );

vtkSmartPointer<vtkRenderWindow> renwin =
vtkSmartPointer<vtkRenderWindow>::New();
renwin->AddRenderer( ren );

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

renwin->Render();

iren->Start();

circle->Delete();

return EXIT_SUCCESS;
}
```

# Please try the new VTKExamples website.

## CMakeLists.txt

```cmake_minimum_required(VERSION 2.8)

PROJECT(DecimatePolyline)

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

add_executable(DecimatePolyline MACOSX_BUNDLE DecimatePolyline.cxx)

if(VTK_LIBRARIES)
target_link_libraries(DecimatePolyline \${VTK_LIBRARIES})
else()
target_link_libraries(DecimatePolyline vtkHybrid vtkWidgets)
endif()
```

## Download and Build DecimatePolyline

Click here to download DecimatePolyline. and its CMakeLists.txt file.

Once the tarball DecimatePolyline.tar has been downloaded and extracted,

```cd DecimatePolyline/build
```
• If VTK is installed:
```cmake ..
```
• If VTK is not installed but compiled on your system, you will need to specify the path to your VTK build:
```cmake -DVTK_DIR:PATH=/home/me/vtk_build ..
```

Build the project:

```make
```

and run it:

```./DecimatePolyline
```

WINDOWS USERS PLEASE NOTE: Be sure to add the VTK bin directory to your path. This will resolve the VTK dll's at run time.