# DecimatePolyline

vtk-examples/Cxx/PolyData/DecimatePolyline

### Description¶

This example shows how to decimate a polyline.

Question

### Code¶

DecimatePolyline.cxx

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

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

vtkNew<vtkPolyData> circle;
vtkNew<vtkPoints> points;
vtkNew<vtkCellArray> lines;
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);

vtkNew<vtkPolyDataMapper> c_mapper;
c_mapper->SetInputData(circle);

vtkNew<vtkNamedColors> colors;

vtkNew<vtkActor> c_actor;
c_actor->SetMapper(c_mapper);
c_actor->GetProperty()->SetColor(colors->GetColor3d("Banana").GetData());
c_actor->GetProperty()->SetLineWidth(3);

vtkNew<vtkDecimatePolylineFilter> decimate;
decimate->SetInputData(circle);
decimate->SetTargetReduction(0.95);
decimate->Update();

vtkNew<vtkPolyDataMapper> d_mapper;
d_mapper->SetInputConnection(decimate->GetOutputPort());

vtkNew<vtkActor> d_actor;
d_actor->SetMapper(d_mapper);
d_actor->GetProperty()->SetColor(colors->GetColor3d("Tomato").GetData());
d_actor->GetProperty()->SetLineWidth(3);

vtkNew<vtkRenderer> ren;
ren->SetBackground(colors->GetColor3d("SlateGray").GetData());

vtkNew<vtkRenderWindow> renwin;
renwin->SetSize(640, 480);
renwin->SetWindowName("DecimatePolyline");

vtkNew<vtkRenderWindowInteractor> iren;
iren->SetRenderWindow(renwin);

renwin->Render();

iren->Start();

return EXIT_SUCCESS;
}


### CMakeLists.txt¶

cmake_minimum_required(VERSION 3.12 FATAL_ERROR)

project(DecimatePolyline)

find_package(VTK COMPONENTS
CommonColor
CommonCore
CommonDataModel
FiltersCore
InteractionStyle
RenderingContextOpenGL2
RenderingCore
RenderingFreeType
RenderingGL2PSOpenGL2
RenderingOpenGL2
)

if (NOT VTK_FOUND)
message(FATAL_ERROR "DecimatePolyline: Unable to find the VTK build folder.")
endif()

# Prevent a "command line is too long" failure in Windows.
set(CMAKE_NINJA_FORCE_RESPONSE_FILE "ON" CACHE BOOL "Force Ninja to use response files.")
target_link_libraries(DecimatePolyline PRIVATE ${VTK_LIBRARIES} ) # vtk_module_autoinit is needed vtk_module_autoinit( TARGETS DecimatePolyline MODULES${VTK_LIBRARIES}
)


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

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