# Triangle

vtk-examples/Cxx/GeometricObjects/Triangle

### Description¶

The triangle is a primary two-dimensional cell. The triangle is defined by a counterclockwise ordered list of three points. The order of the points specifies the direction of the surface normal using the right-hand rule.

Other languages

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

Question

### Code¶

Triangle.cxx

#include <vtkActor.h>
#include <vtkCellArray.h>
#include <vtkNamedColors.h>
#include <vtkPolyData.h>
#include <vtkPolyDataMapper.h>
#include <vtkProperty.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>
#include <vtkSmartPointer.h>
#include <vtkTriangle.h>

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

// Create a triangle
vtkNew<vtkPoints> points;
points->InsertNextPoint(1.0, 0.0, 0.0);
points->InsertNextPoint(0.0, 0.0, 0.0);
points->InsertNextPoint(0.0, 1.0, 0.0);

vtkNew<vtkTriangle> triangle;
triangle->GetPointIds()->SetId(0, 0);
triangle->GetPointIds()->SetId(1, 1);
triangle->GetPointIds()->SetId(2, 2);

vtkNew<vtkCellArray> triangles;
triangles->InsertNextCell(triangle);

// Create a polydata object
vtkNew<vtkPolyData> trianglePolyData;

// Add the geometry and topology to the polydata
trianglePolyData->SetPoints(points);
trianglePolyData->SetPolys(triangles);

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

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

// Create a renderer, render window, and an interactor
vtkNew<vtkRenderer> renderer;
vtkNew<vtkRenderWindow> renderWindow;
renderWindow->SetWindowName("Triangle");
vtkNew<vtkRenderWindowInteractor> renderWindowInteractor;
renderWindowInteractor->SetRenderWindow(renderWindow);

// Add the actors to the scene
renderer->SetBackground(colors->GetColor3d("DarkGreen").GetData());

// Render and interact
renderWindow->Render();
renderWindowInteractor->Start();

return EXIT_SUCCESS;
}


### CMakeLists.txt¶

cmake_minimum_required(VERSION 3.12 FATAL_ERROR)

project(Triangle)

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

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


cd Triangle/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:

./Triangle


WINDOWS USERS

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