# Polygon

vtk-examples/Cxx/GeometricObjects/Polygon

### Description¶

The polygon is a primary two-dimensional cell. The polygon is defined by an ordered list of three or more points lying in a plane. The polygon normal is implicitly defined by a counterclockwise ordering of its points using the right-hand rule.

The polygon may be nonconvex, but may not have internal loops, and it cannot self-intersect. The polygon has n edges, where n is the number of points in the polygon.

Other languages

See (Python), (Java), (CSharp)

Question

### Code¶

Polygon.cxx

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

int main(int, char*[])
{
vtkNew<vtkNamedColors> colors;

// Setup four points
vtkNew<vtkPoints> points;
points->InsertNextPoint(0.0, 0.0, 0.0);
points->InsertNextPoint(1.0, 0.0, 0.0);
points->InsertNextPoint(1.0, 1.0, 0.0);
points->InsertNextPoint(0.0, 1.0, 0.0);

// Create the polygon
vtkNew<vtkPolygon> polygon;
polygon->GetPointIds()->SetId(0, 0);
polygon->GetPointIds()->SetId(1, 1);
polygon->GetPointIds()->SetId(2, 2);
polygon->GetPointIds()->SetId(3, 3);

// Add the polygon to a list of polygons
vtkNew<vtkCellArray> polygons;
polygons->InsertNextCell(polygon);

// Create a PolyData
vtkNew<vtkPolyData> polygonPolyData;
polygonPolyData->SetPoints(points);
polygonPolyData->SetPolys(polygons);

// Create a mapper and actor
vtkNew<vtkPolyDataMapper> mapper;
mapper->SetInputData(polygonPolyData);

vtkNew<vtkActor> actor;
actor->SetMapper(mapper);
actor->GetProperty()->SetColor(colors->GetColor3d("Silver").GetData());

// Visualize
vtkNew<vtkRenderer> renderer;
vtkNew<vtkRenderWindow> renderWindow;
renderWindow->SetWindowName("Polygon");
vtkNew<vtkRenderWindowInteractor> renderWindowInteractor;
renderWindowInteractor->SetRenderWindow(renderWindow);

renderer->SetBackground(colors->GetColor3d("Salmon").GetData());
renderWindow->Render();
renderWindowInteractor->Start();

return EXIT_SUCCESS;
}


### CMakeLists.txt¶

cmake_minimum_required(VERSION 3.12 FATAL_ERROR)

project(Polygon)

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

if (NOT VTK_FOUND)
message(FATAL_ERROR "Polygon: 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(Polygon PRIVATE ${VTK_LIBRARIES} ) # vtk_module_autoinit is needed vtk_module_autoinit( TARGETS Polygon MODULES${VTK_LIBRARIES}
)


cd Polygon/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:

./Polygon


WINDOWS USERS

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