# VTK/Examples/Cxx/GeometricObjects/PolygonIntersection

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## PolygonIntersection.cxx

#include <vtkSmartPointer.h>
#include <vtkPoints.h>
#include <vtkPolygon.h>

int main(int, char*[])
{
// Create a square in the XY plane
vtkSmartPointer<vtkPoints> points = vtkSmartPointer<vtkPoints>::New();
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
vtkSmartPointer<vtkPolygon> polygon = vtkSmartPointer<vtkPolygon>::New();
polygon->GetPoints()->DeepCopy(points);
polygon->GetPointIds()->SetNumberOfIds(4); // 4 corners of the square
polygon->GetPointIds()->SetId(0, 0);
polygon->GetPointIds()->SetId(1, 1);
polygon->GetPointIds()->SetId(2, 2);
polygon->GetPointIds()->SetId(3, 3);

// Inputs
double p1[3] = {0.1, 0, -1.0};
double p2[3] = {0.1, 0, 1.0};
double tolerance = 0.001;
// Outputs
double t; // Parametric coordinate of intersection (0 (corresponding to p1) to 1 (corresponding to p2))
double x[3]; // The coordinate of the intersection
double pcoords[3];
int subId;

vtkIdType iD = polygon->IntersectWithLine(p1, p2, tolerance, t, x, pcoords, subId);

std::cout << "intersected? " << iD << std::endl;
std::cout << "intersection: " << x[0] << " " << x[1] << " " << x[2] << std::endl;

return EXIT_SUCCESS;
}

# Please try the new VTKExamples website.

## CMakeLists.txt

cmake_minimum_required(VERSION 2.8)

PROJECT(PolygonIntersection)

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

if(VTK_LIBRARIES)
else()
endif()

cd PolygonIntersection/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:

./PolygonIntersection

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.