# TensorEllipsoids

vtk-examples/Cxx/VisualizationAlgorithms/TensorEllipsoids

### Description¶

This example visualizes the analytical results of Boussinesq's problem from Saada. The figure shows the results by displaying the scaled and oriented principal axes as tensor ellipsoids representing the stress tensor. (These are called tensor axes.)

Other languages

See (Python)

Question

### Code¶

TensorEllipsoids.cxx

// Translated from tenEllip.tcl

#include <vtkActor.h>
#include <vtkCamera.h>
#include <vtkColorSeries.h>
#include <vtkConeSource.h>
#include <vtkImageDataGeometryFilter.h>
#include <vtkLookupTable.h>
#include <vtkNamedColors.h>
#include <vtkNew.h>
#include <vtkOutlineFilter.h>
#include <vtkPolyDataMapper.h>
#include <vtkPolyDataNormals.h>
#include <vtkProp3D.h>
#include <vtkProperty.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>
#include <vtkSphereSource.h>
#include <vtkTensorGlyph.h>

namespace {
void MakeLogLUT(vtkLookupTable* lut);
}

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

// Create the RenderWindow, Renderer and interactive renderer.
//
vtkNew<vtkRenderer> ren;
vtkNew<vtkRenderWindow> renWin;
vtkNew<vtkRenderWindowInteractor> iren;
iren->SetRenderWindow(renWin);

// Generate the tensors.
ptLoad->SetModelBounds(-10, 10, -10, 10, -10, 10);

// Extract a plane of data.
vtkNew<vtkImageDataGeometryFilter> plane;
plane->SetExtent(2, 2, 0, 99, 0, 99);

// Generate the ellipsoids.
vtkNew<vtkSphereSource> sphere;
sphere->SetThetaResolution(8);
sphere->SetPhiResolution(8);
vtkNew<vtkTensorGlyph> tensorEllipsoids;
tensorEllipsoids->SetSourceConnection(sphere->GetOutputPort());
tensorEllipsoids->SetScaleFactor(10);
tensorEllipsoids->ClampScalingOn();

vtkNew<vtkPolyDataNormals> ellipNormals;
ellipNormals->SetInputConnection(tensorEllipsoids->GetOutputPort());

// Map contour.
vtkNew<vtkLookupTable> lut;
MakeLogLUT(lut);
vtkNew<vtkPolyDataMapper> tensorEllipsoidsMapper;
tensorEllipsoidsMapper->SetInputConnection(ellipNormals->GetOutputPort());
tensorEllipsoidsMapper->SetLookupTable(lut);
plane->Update(); // force update for scalar range
tensorEllipsoidsMapper->SetScalarRange(plane->GetOutput()->GetScalarRange());

vtkNew<vtkActor> tensorActor;
tensorActor->SetMapper(tensorEllipsoidsMapper);

// Create an outline around the data.
//
vtkNew<vtkOutlineFilter> outline;

vtkNew<vtkPolyDataMapper> outlineMapper;
outlineMapper->SetInputConnection(outline->GetOutputPort());

vtkNew<vtkActor> outlineActor;
outlineActor->SetMapper(outlineMapper);
outlineActor->GetProperty()->SetColor(colors->GetColor3d("Black").GetData());

// Create a cone whose apex indicates the application of load.
//
vtkNew<vtkConeSource> coneSrc;
coneSrc->SetHeight(2);
vtkNew<vtkPolyDataMapper> coneMap;
coneMap->SetInputConnection(coneSrc->GetOutputPort());
vtkNew<vtkActor> coneActor;
coneActor->SetMapper(coneMap);
coneActor->SetPosition(0, 0, 11);
coneActor->RotateY(90);
coneActor->GetProperty()->SetColor(colors->GetColor3d("Red").GetData());

vtkNew<vtkCamera> camera;
camera->SetFocalPoint(0.113766, -1.13665, -1.01919);
camera->SetPosition(-29.4886, -63.1488, 26.5807);
camera->SetViewAngle(24.4617);
camera->SetViewUp(0.17138, 0.331163, 0.927879);
camera->SetClippingRange(1, 100);

ren->SetBackground(colors->GetColor3d("WhiteSmoke").GetData());
ren->SetActiveCamera(camera);

renWin->SetSize(512, 512);
renWin->SetWindowName("TensorEllipsoids");

iren->Initialize();
renWin->Render();
iren->Start();

return EXIT_SUCCESS;
}

namespace {
void MakeLogLUT(vtkLookupTable* lut)
{
// Make the lookup using a Brewer palette.
vtkNew<vtkColorSeries> colorSeries;
colorSeries->SetNumberOfColors(8);
int colorSeriesEnum = colorSeries->BREWER_DIVERGING_SPECTRAL_8;
colorSeries->SetColorScheme(colorSeriesEnum);
lut->SetScaleToLog10();
colorSeries->BuildLookupTable(lut, colorSeries->ORDINAL);
lut->SetNanColor(1, 0, 0, 1);
// Original
// lut->SetScaleToLog10();
// lut->SetHueRange(.6667, 0.0);
// lut->Build();
}
} // namespace


### CMakeLists.txt¶

cmake_minimum_required(VERSION 3.12 FATAL_ERROR)

project(TensorEllipsoids)

find_package(VTK COMPONENTS
CommonColor
CommonCore
FiltersCore
FiltersGeometry
FiltersModeling
ImagingHybrid
InteractionStyle
RenderingContextOpenGL2
RenderingCore
RenderingFreeType
RenderingGL2PSOpenGL2
RenderingOpenGL2
)

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


cd TensorEllipsoids/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:

./TensorEllipsoids


WINDOWS USERS

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