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.)

Info

See Figure 6-22b in Chapter 6 the VTK Textbook.

Other languages

See (Python), (PythonicAPI)

Question

If you have a question about this example, please use the VTK Discourse Forum

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 <vtkPointLoad.h>
#include <vtkPolyDataMapper.h>
#include <vtkPolyDataNormals.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;
  renWin->AddRenderer(ren);
  vtkNew<vtkRenderWindowInteractor> iren;
  iren->SetRenderWindow(renWin);

  // Generate the tensors.
  vtkNew<vtkPointLoad> ptLoad;
  ptLoad->SetLoadValue(100.0);
  ptLoad->SetSampleDimensions(6, 6, 6);
  ptLoad->ComputeEffectiveStressOn();
  ptLoad->SetModelBounds(-10, 10, -10, 10, -10, 10);

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

  // Generate the ellipsoids.
  vtkNew<vtkSphereSource> sphere;
  sphere->SetThetaResolution(8);
  sphere->SetPhiResolution(8);
  vtkNew<vtkTensorGlyph> tensorEllipsoids;
  tensorEllipsoids->SetInputConnection(ptLoad->GetOutputPort());
  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;
  outline->SetInputConnection(ptLoad->GetOutputPort());

  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->SetRadius(0.5);
  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->AddActor(tensorActor);
  ren->AddActor(outlineActor);
  ren->AddActor(coneActor);
  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
  FiltersSources
  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.")
add_executable(TensorEllipsoids MACOSX_BUNDLE TensorEllipsoids.cxx )
  target_link_libraries(TensorEllipsoids PRIVATE ${VTK_LIBRARIES}
)
# vtk_module_autoinit is needed
vtk_module_autoinit(
  TARGETS TensorEllipsoids
  MODULES ${VTK_LIBRARIES}
)

Download and Build TensorEllipsoids¶

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

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.