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

If you have a question about this example, please use the VTK Discourse Forum

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()->SetNumberOfIds(4); // make a quad
  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");
  renderWindow->AddRenderer(renderer);
  vtkNew<vtkRenderWindowInteractor> renderWindowInteractor;
  renderWindowInteractor->SetRenderWindow(renderWindow);

  renderer->AddActor(actor);
  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.")
add_executable(Polygon MACOSX_BUNDLE Polygon.cxx )
  target_link_libraries(Polygon PRIVATE ${VTK_LIBRARIES}
)
# vtk_module_autoinit is needed
vtk_module_autoinit(
  TARGETS Polygon
  MODULES ${VTK_LIBRARIES}
)

Download and Build Polygon¶

Click here to download Polygon and its CMakeLists.txt file. Once the tarball Polygon.tar has been downloaded and extracted,

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.