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# TensorGlyph

VTKEx/Cxx/Visualization/TensorGlyph

### Description

This example demonstrates how to apply a rotation+scaling matrix to each point in a data set. We use a cube as the glyph so that simple rotations are easy to interpret. Specifically, we glyph one point with no rotation/scaling, and a second point with a rotation of 45 degrees around the x axis.

Question

If you have a simple question about this example contact us at VTKExProject If your question is more complex and may require extended discussion, please use the VTK Discourse Forum

### Code

TensorGlyph.cxx

    #include <vtkActor.h>
    #include <vtkCellArray.h>
    #include <vtkDoubleArray.h>
    #include <vtkMath.h>
    #include <vtkPointData.h>
    #include <vtkPoints.h>
    #include <vtkPointSource.h>
    #include <vtkPolyDataMapper.h>
    #include <vtkPolyData.h>
    #include <vtkRenderer.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkSmartPointer.h>
    #include <vtkCubeSource.h>
    #include <vtkTensorGlyph.h>
    #include <vtkVertexGlyphFilter.h>

    int main(int, char *[])
    {
        // Setup points
        vtkSmartPointer<vtkPoints> points =
          vtkSmartPointer<vtkPoints>::New();
        points->InsertNextPoint(0.0, 0.0, 0.0);
        points->InsertNextPoint(5.0, 0.0, 0.0);

        vtkSmartPointer<vtkPolyData> polyData = vtkSmartPointer<vtkPolyData>::New();
        polyData->SetPoints(points);

        vtkSmartPointer<vtkDoubleArray> tensors = vtkSmartPointer<vtkDoubleArray>::New();
        tensors->SetNumberOfTuples(2);
        tensors->SetNumberOfComponents(9);

        tensors->InsertTuple9(0,1,0,0,0,1,0,0,0,1);
        tensors->InsertTuple9(1,1,0,0,0,.7,.7,0,-.7,.7); // column major

        polyData->GetPointData()->SetTensors(tensors);

        vtkSmartPointer<vtkCubeSource> cubeSource = vtkSmartPointer<vtkCubeSource>::New();
        cubeSource->Update();

        vtkSmartPointer<vtkTensorGlyph> tensorGlyph = vtkSmartPointer<vtkTensorGlyph>::New();
        tensorGlyph->SetInputData(polyData);
        tensorGlyph->SetSourceConnection(cubeSource->GetOutputPort());
        tensorGlyph->ColorGlyphsOff();
        tensorGlyph->ThreeGlyphsOff();
        tensorGlyph->ExtractEigenvaluesOff();
        tensorGlyph->Update();

        vtkSmartPointer<vtkPolyDataMapper> mapper = vtkSmartPointer<vtkPolyDataMapper>::New();
        mapper->SetInputData(tensorGlyph->GetOutput());

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

        vtkSmartPointer<vtkRenderer> renderer = vtkSmartPointer<vtkRenderer>::New();
        renderer->AddActor(actor);

        vtkSmartPointer<vtkRenderWindow> renderWindow = vtkSmartPointer<vtkRenderWindow>::New();
        renderWindow->AddRenderer( renderer );

        vtkSmartPointer<vtkRenderWindowInteractor> interactor =
            vtkSmartPointer<vtkRenderWindowInteractor>::New();
        interactor->SetRenderWindow( renderWindow );
        renderWindow->Render();
        interactor->Start();

        return 0;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

    project(TensorGlyph)

    find_package(VTK COMPONENTS
      vtkCommonCore
      vtkCommonDataModel
      vtkFiltersCore
      vtkFiltersGeneral
      vtkFiltersSources
      vtkInteractionStyle
      vtkRenderingContextOpenGL2
      vtkRenderingCore
      vtkRenderingFreeType
      vtkRenderingGL2PSOpenGL2
      vtkRenderingOpenGL2 QUIET)
    if (NOT VTK_FOUND)
      message("Skipping TensorGlyph: ${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(TensorGlyph MACOSX_BUNDLE TensorGlyph.cxx )
      target_link_libraries(TensorGlyph PRIVATE ${VTK_LIBRARIES})
    else ()
      # include all components
      add_executable(TensorGlyph MACOSX_BUNDLE TensorGlyph.cxx )
      target_link_libraries(TensorGlyph PRIVATE ${VTK_LIBRARIES})
      # vtk_module_autoinit is needed
      vtk_module_autoinit(
        TARGETS TensorGlyph
        MODULES ${VTK_LIBRARIES}
        )
    endif ()

### Download and Build TensorGlyph

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

    cd TensorGlyph/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:

    ./TensorGlyph

WINDOWS USERS

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