# TriangleColoredPoints

VTKExamples/Cxx/PolyData/TriangleColoredPoints

### Description

This example shows how by adding a color to each vertex of a triangle, the triangle's color will be smoothly varying between the colors of the vertices.

Other Languages

See (Python), (Java)

### Code

TriangleColoredPoints.cxx

    #include <vtkSmartPointer.h>
    #include <vtkPoints.h>
    #include <vtkXMLPolyDataWriter.h>
    #include <vtkPolyData.h>
    #include <vtkPointData.h>
    #include <vtkCellArray.h>
    #include <vtkTriangle.h>
    #include <vtkPolyDataMapper.h>
    #include <vtkActor.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderer.h>
    #include <vtkRenderWindowInteractor.h>

    // For compatibility with new VTK generic data arrays
    #ifdef vtkGenericDataArray_h
    #define InsertNextTupleValue InsertNextTypedTuple
    #endif

    int main(int, char *[])
    {
      // Setup points
      vtkSmartPointer<vtkPoints> points =
        vtkSmartPointer<vtkPoints>::New();
      points->InsertNextPoint(1.0, 0.0, 0.0);
      points->InsertNextPoint(0.0, 0.0, 0.0);
      points->InsertNextPoint(0.0, 1.0, 0.0);

      // Define some colors
      unsigned char red[3] = {255, 0, 0};
      unsigned char green[3] = {0, 255, 0};
      unsigned char blue[3] = {0, 0, 255};

      // Setup the colors array
      vtkSmartPointer<vtkUnsignedCharArray> colors =
        vtkSmartPointer<vtkUnsignedCharArray>::New();
      colors->SetNumberOfComponents(3);
      colors->SetName("Colors");

      // Add the three colors we have created to the array
      colors->InsertNextTupleValue(red);
      colors->InsertNextTupleValue(green);
      colors->InsertNextTupleValue(blue);

      // Create a triangle
      vtkSmartPointer<vtkCellArray> triangles =
        vtkSmartPointer<vtkCellArray>::New();
      vtkSmartPointer<vtkTriangle> triangle =
        vtkSmartPointer<vtkTriangle>::New();
      triangle->GetPointIds()->SetId(0, 0);
      triangle->GetPointIds()->SetId(1, 1);
      triangle->GetPointIds()->SetId(2, 2);
      triangles->InsertNextCell(triangle);

      // Create a polydata object and add everything to it
      vtkSmartPointer<vtkPolyData> polydata =
        vtkSmartPointer<vtkPolyData>::New();
      polydata->SetPoints(points);
      polydata->SetPolys(triangles);
      polydata->GetPointData()->SetScalars(colors);

      // Visualize
      vtkSmartPointer<vtkPolyDataMapper> mapper =
        vtkSmartPointer<vtkPolyDataMapper>::New();
      mapper->SetInputData(polydata);

      vtkSmartPointer<vtkActor> actor =
        vtkSmartPointer<vtkActor>::New();
      actor->SetMapper(mapper);

      vtkSmartPointer<vtkRenderer> renderer =
        vtkSmartPointer<vtkRenderer>::New();
      vtkSmartPointer<vtkRenderWindow> renderWindow =
        vtkSmartPointer<vtkRenderWindow>::New();
      renderWindow->AddRenderer(renderer);
      vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor =
        vtkSmartPointer<vtkRenderWindowInteractor>::New();
      renderWindowInteractor->SetRenderWindow(renderWindow);

      renderer->AddActor(actor);

      renderWindow->Render();
      renderWindowInteractor->Start();

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

    project(TriangleColoredPoints)

    find_package(VTK COMPONENTS
      vtkCommonCore
      vtkCommonDataModel
      vtkIOXML
      vtkInteractionStyle
      vtkRenderingCore
      vtkRenderingFreeType
      vtkRenderingOpenGL2 QUIET)
    if (NOT VTK_FOUND)
      message("Skipping TriangleColoredPoints: ${VTK_NOT_FOUND_MESSAGE}")
      return ()
    endif()
    message (STATUS "VTK_VERSION: ${VTK_VERSION}")
    if (VTK_VERSION VERSION_LESS "8.90.0")
      # old system
      include(${VTK_USE_FILE})
      add_executable(TriangleColoredPoints MACOSX_BUNDLE TriangleColoredPoints.cxx )
      target_link_libraries(TriangleColoredPoints PRIVATE ${VTK_LIBRARIES})
    else ()
      # include all components
      add_executable(TriangleColoredPoints MACOSX_BUNDLE TriangleColoredPoints.cxx )
      target_link_libraries(TriangleColoredPoints PRIVATE ${VTK_LIBRARIES})
      # vtk_module_autoinit is needed
      vtk_module_autoinit(
        TARGETS TriangleColoredPoints
        MODULES ${VTK_LIBRARIES}
        )
    endif ()

### Download and Build TriangleColoredPoints

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

    cd TriangleColoredPoints/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:

    ./TriangleColoredPoints

WINDOWS USERS

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