# PolygonIntersection

vtk-examples/Cxx/GeometricObjects/PolygonIntersection

Other languages

See (Python), (CSharp)

Question

### Code¶

PolygonIntersection.cxx

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

int main(int, char*[])
{
// Create a square in the XY plane
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->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 = {0.1, 0, -1.0};
double p2 = {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; // The coordinate of the intersection
double pcoords;
int subId;

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

auto res = (iD == 1) ? "Yes" : "No";
std::cout << "intersected? " << res << std::endl;
std::cout << "intersection: " << x << " " << x << " " << x
<< std::endl;

return EXIT_SUCCESS;
}


### CMakeLists.txt¶

cmake_minimum_required(VERSION 3.12 FATAL_ERROR)

project(PolygonIntersection)

find_package(VTK COMPONENTS
CommonCore
CommonDataModel
)

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


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

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