# TensorGlyph

vtk-examples/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 question about this example, please use the VTK Discourse Forum

### Code¶

TensorGlyph.cxx

#include <vtkActor.h>
#include <vtkCubeSource.h>
#include <vtkDoubleArray.h>
#include <vtkNamedColors.h>
#include <vtkNew.h>
#include <vtkPointData.h>
#include <vtkPoints.h>
#include <vtkPolyData.h>
#include <vtkPolyDataMapper.h>
#include <vtkProperty.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>
#include <vtkTensorGlyph.h>

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

// Setup points.
vtkNew<vtkPoints> points;
points->InsertNextPoint(0.0, 0.0, 0.0);
points->InsertNextPoint(5.0, 0.0, 0.0);

vtkNew<vtkPolyData> polyData;
polyData->SetPoints(points);

vtkNew<vtkDoubleArray> tensors;
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, 0.7, 0.7, 0, -0.7, 0.7); // column major

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

vtkNew<vtkCubeSource> cubeSource;
cubeSource->Update();

vtkNew<vtkTensorGlyph> tensorGlyph;
tensorGlyph->SetInputData(polyData);
tensorGlyph->SetSourceConnection(cubeSource->GetOutputPort());
tensorGlyph->ColorGlyphsOff();
tensorGlyph->ThreeGlyphsOff();
tensorGlyph->ExtractEigenvaluesOff();
tensorGlyph->Update();

vtkNew<vtkPolyDataMapper> mapper;
mapper->SetInputData(tensorGlyph->GetOutput());

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

vtkNew<vtkRenderer> renderer;
renderer->AddActor(actor);
renderer->SetBackground(colors->GetColor3d("SlateGray").GetData());

vtkNew<vtkRenderWindow> renderWindow;
renderWindow->AddRenderer(renderer);
renderWindow->SetWindowName("TensorGlyph");

vtkNew<vtkRenderWindowInteractor> interactor;
interactor->SetRenderWindow(renderWindow);
renderWindow->Render();
interactor->Start();

return EXIT_SUCCESS;
}

### CMakeLists.txt¶

cmake_minimum_required(VERSION 3.12 FATAL_ERROR)

project(TensorGlyph)

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

if (NOT VTK_FOUND)
message(FATAL_ERROR "TensorGlyph: 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.")
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}
)

### 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.