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QuadraticHexahedronDemo

vtk-examples/Cxx/GeometricObjects/QuadraticHexahedronDemo

Description

This example shows the effect of changing the chord length error for a vtkQuadraticHexahedron.

Other languages

See (Python)

Question

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

Code

QuadraticHexahedronDemo.cxx

#include <vtkActor.h>
#include <vtkActor2D.h>
#include <vtkCellIterator.h>
#include <vtkCommand.h>
#include <vtkDataSetMapper.h>
#include <vtkGenericCell.h>
#include <vtkGlyph3D.h>
#include <vtkMinimalStandardRandomSequence.h>
#include <vtkNamedColors.h>
#include <vtkNew.h>
#include <vtkPoints.h>
#include <vtkProperty.h>
#include <vtkQuadraticHexahedron.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>
#include <vtkSliderRepresentation2D.h>
#include <vtkSliderWidget.h>
#include <vtkSmartPointer.h>
#include <vtkSphereSource.h>
#include <vtkTessellatorFilter.h>
#include <vtkTextMapper.h>
#include <vtkTextProperty.h>
#include <vtkUnstructuredGrid.h>

#include <map>
#include <sstream>

namespace {
vtkSmartPointer<vtkUnstructuredGrid> MakeQuadraticHexahedron();

void MakeWidget(vtkSmartPointer<vtkSliderWidget>& widget,
                vtkSmartPointer<vtkTessellatorFilter>& tessellate,
                vtkSmartPointer<vtkTextMapper>& textMapper,
                vtkSmartPointer<vtkRenderWindowInteractor>& interactor);
} // namespace

int main(int, char*[])
{
  vtkNew<vtkNamedColors> namedColors;
  auto uGrid = MakeQuadraticHexahedron();

  vtkSmartPointer<vtkTessellatorFilter> tessellate =
      vtkSmartPointer<vtkTessellatorFilter>::New();
  tessellate->SetInputData(uGrid);
  tessellate->SetChordError(0.035);
  tessellate->Update();

  typedef std::map<const char*, int> CellContainer;
  CellContainer cellMap;

  int numTets = 0;
  vtkNew<vtkGenericCell> cell;
  auto it = tessellate->GetOutput()->NewCellIterator();
  for (it->InitTraversal(); !it->IsDoneWithTraversal(); it->GoToNextCell())
  {
    it->GetCell(cell);
    cellMap[cell->GetRepresentativeCell()->GetClassName()]++;
    ++numTets;
  }
  it->Delete();

  vtkSmartPointer<vtkDataSetMapper> mapper =
      vtkSmartPointer<vtkDataSetMapper>::New();
  mapper->SetInputConnection(tessellate->GetOutputPort());
  mapper->ScalarVisibilityOff();

  // Create an actor for the grid
  vtkNew<vtkActor> actor;
  actor->SetMapper(mapper);
  actor->GetProperty()->SetDiffuseColor(
      namedColors->GetColor3d("Tomato").GetData());
  actor->GetProperty()->SetEdgeColor(
      namedColors->GetColor3d("IvoryBlack").GetData());
  actor->GetProperty()->EdgeVisibilityOn();

  vtkNew<vtkSphereSource> sphereSource;
  sphereSource->SetRadius(0.02);

  vtkNew<vtkGlyph3D> glyph3D;
  glyph3D->SetInputData(uGrid);
  glyph3D->SetSourceConnection(sphereSource->GetOutputPort());
  glyph3D->ScalingOff();
  glyph3D->Update();

  vtkNew<vtkDataSetMapper> glyph3DMapper;
  glyph3DMapper->SetInputConnection(glyph3D->GetOutputPort());
  glyph3DMapper->ScalarVisibilityOff();

  vtkNew<vtkActor> glyph3DActor;
  glyph3DActor->SetMapper(glyph3DMapper);
  glyph3DActor->GetProperty()->SetColor(
      namedColors->GetColor3d("Banana").GetData());

  vtkNew<vtkTextProperty> textProperty;
  textProperty->SetFontSize(24);

  std::stringstream ss;
  ss << "# of Tetras: " << numTets << std::endl;
  vtkSmartPointer<vtkTextMapper> textMapper =
      vtkSmartPointer<vtkTextMapper>::New();
  textMapper->SetInput(ss.str().c_str());
  textMapper->SetTextProperty(textProperty);

  vtkNew<vtkActor2D> textActor;
  textActor->SetMapper(textMapper);
  textActor->SetPosition(10, 400);

  // Visualize
  vtkNew<vtkRenderer> renderer;
  renderer->UseHiddenLineRemovalOn();

  vtkNew<vtkRenderWindow> renderWindow;
  renderWindow->SetWindowName("QuadraticHexahedronDemo");
  renderWindow->AddRenderer(renderer);
  renderWindow->SetSize(640, 512);
  vtkSmartPointer<vtkRenderWindowInteractor> interactor =
      vtkSmartPointer<vtkRenderWindowInteractor>::New();
  interactor->SetRenderWindow(renderWindow);

  vtkSmartPointer<vtkSliderWidget> widget =
      vtkSmartPointer<vtkSliderWidget>::New();
  MakeWidget(widget, tessellate, textMapper, interactor);

  renderer->AddActor(actor);
  renderer->AddActor(glyph3DActor);
  renderer->AddViewProp(textActor);
  renderer->SetBackground(namedColors->GetColor3d("SlateGray").GetData());

  renderWindow->Render();

  interactor->Start();

  return EXIT_SUCCESS;
}

namespace {
// These callbacks do the actual work.
// Callbacks for the interactions
class SliderCallbackChordError : public vtkCommand
{
public:
  static SliderCallbackChordError* New()
  {
    return new SliderCallbackChordError;
  }
  virtual void Execute(vtkObject* caller, unsigned long, void*)
  {
    vtkSliderWidget* sliderWidget = reinterpret_cast<vtkSliderWidget*>(caller);
    double value = static_cast<vtkSliderRepresentation2D*>(
                       sliderWidget->GetRepresentation())
                       ->GetValue();
    this->Tessellator->SetChordError(value);
    this->Tessellator->SetMaximumNumberOfSubdivisions(4);
    this->Tessellator->Update();

    typedef std::map<const char*, int> CellContainer;
    CellContainer cellMap;

    int numTets = 0;
    vtkNew<vtkGenericCell> cell;
    auto it = this->Tessellator->GetOutput()->NewCellIterator();
    for (it->InitTraversal(); !it->IsDoneWithTraversal(); it->GoToNextCell())
    {
      it->GetCell(cell);
      cellMap[cell->GetRepresentativeCell()->GetClassName()]++;
      ++numTets;
    }
    std::stringstream ss;
    ss << "# of Tetras: " << numTets << std::endl;
    TextMapper->SetInput(ss.str().c_str());
  }
  SliderCallbackChordError() : Tessellator(0), TextMapper(0)
  {
  }
  vtkTessellatorFilter* Tessellator;
  vtkTextMapper* TextMapper;
};

void MakeWidget(vtkSmartPointer<vtkSliderWidget>& widget,
                vtkSmartPointer<vtkTessellatorFilter>& tessellate,
                vtkSmartPointer<vtkTextMapper>& textMapper,
                vtkSmartPointer<vtkRenderWindowInteractor>& interactor)
{
  // Setup a slider widget for each varying parameter
  double tubeWidth(0.008);
  double sliderLength(0.008);
  double titleHeight(0.04);
  double labelHeight(0.04);

  vtkNew<vtkSliderRepresentation2D> sliderRepChordError;

  sliderRepChordError->SetMinimumValue(0.0);
  sliderRepChordError->SetMaximumValue(0.07);
  sliderRepChordError->SetValue(tessellate->GetChordError());
  sliderRepChordError->SetTitleText("Chord error");

  sliderRepChordError->GetPoint1Coordinate()
      ->SetCoordinateSystemToNormalizedDisplay();
  sliderRepChordError->GetPoint1Coordinate()->SetValue(0.1, 0.1);
  sliderRepChordError->GetPoint2Coordinate()
      ->SetCoordinateSystemToNormalizedDisplay();
  sliderRepChordError->GetPoint2Coordinate()->SetValue(0.9, 0.1);

  sliderRepChordError->SetTubeWidth(tubeWidth);
  sliderRepChordError->SetSliderLength(sliderLength);
  sliderRepChordError->SetTitleHeight(titleHeight);
  sliderRepChordError->SetLabelHeight(labelHeight);

  widget->SetInteractor(interactor);
  widget->SetRepresentation(sliderRepChordError);
  widget->SetAnimationModeToAnimate();
  widget->EnabledOn();

  vtkNew<SliderCallbackChordError> callbackChordError;
  callbackChordError->Tessellator = tessellate;
  callbackChordError->TextMapper = textMapper;

  widget->AddObserver(vtkCommand::InteractionEvent, callbackChordError);
}

vtkSmartPointer<vtkUnstructuredGrid> MakeQuadraticHexahedron()
{
  vtkNew<vtkQuadraticHexahedron> aHexahedron;
  vtkNew<vtkPoints> points;

  double* pcoords = aHexahedron->GetParametricCoords();
  vtkNew<vtkMinimalStandardRandomSequence> rng;
  points->SetNumberOfPoints(aHexahedron->GetNumberOfPoints());
  rng->SetSeed(5070); // for testing
  for (auto i = 0; i < aHexahedron->GetNumberOfPoints(); ++i)
  {
    double perturbation[3];
    for (auto j = 0; j < 3; ++j)
    {
      rng->Next();
      perturbation[j] = rng->GetRangeValue(-0.1, 0.1);
    }
    aHexahedron->GetPointIds()->SetId(i, i);
    points->SetPoint(i, *(pcoords + 3 * i) + perturbation[0],
                     *(pcoords + 3 * i + 1) + perturbation[1],
                     *(pcoords + 3 * i + 2) + perturbation[2]);
  }

  // Add the points and hexahedron to an unstructured grid
  vtkSmartPointer<vtkUnstructuredGrid> uGrid =
      vtkSmartPointer<vtkUnstructuredGrid>::New();
  uGrid->SetPoints(points);
  uGrid->InsertNextCell(aHexahedron->GetCellType(), aHexahedron->GetPointIds());

  return uGrid;
}
} // namespace

CMakeLists.txt

cmake_minimum_required(VERSION 3.12 FATAL_ERROR)

project(QuadraticHexahedronDemo)

find_package(VTK COMPONENTS 
)

if (NOT VTK_FOUND)
  message(FATAL_ERROR "QuadraticHexahedronDemo: 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(QuadraticHexahedronDemo MACOSX_BUNDLE QuadraticHexahedronDemo.cxx )
  target_link_libraries(QuadraticHexahedronDemo PRIVATE ${VTK_LIBRARIES}
)
# vtk_module_autoinit is needed
vtk_module_autoinit(
  TARGETS QuadraticHexahedronDemo
  MODULES ${VTK_LIBRARIES}
)

Download and Build QuadraticHexahedronDemo

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

cd QuadraticHexahedronDemo/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:

./QuadraticHexahedronDemo

WINDOWS USERS

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