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AppendFilter

vtk-examples/Cxx/Filtering/AppendFilter


Description

This example loads points into a polydata and an unstructured grid then combines them.

The example should be extended to show cells being combined as well.

Other languages

See (Python)

Question

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

Code

AppendFilter.cxx

#include <vtkActor.h>
#include <vtkAppendFilter.h>
#include <vtkDataSetMapper.h>
#include <vtkGlyph3DMapper.h>
#include <vtkNamedColors.h>
#include <vtkNew.h>
#include <vtkPointSource.h>
#include <vtkPoints.h>
#include <vtkPolyData.h>
#include <vtkProperty.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>
#include <vtkSmartPointer.h>
#include <vtkSphereSource.h>
#include <vtkUnstructuredGrid.h>

namespace {

/**
 * Convert points to glyphs.
 *
 * @param points - The points to glyph
 * @param scale - The scale, used to determine the size of the glyph
 * representing the point, expressed as a fraction of the largest side of the
 * bounding box surrounding the points. e.g. 0.05
 *
 * @return The actor.
 */
vtkSmartPointer<vtkActor> PointToGlyph(vtkPoints* points, double const& scale);

} // namespace

int main(int, char*[])
{
  // Create 5 points (vtkPolyData)
  vtkNew<vtkPointSource> pointSource;
  pointSource->SetNumberOfPoints(5);
  pointSource->Update();

  auto polydata = pointSource->GetOutput();

  std::cout << "There are " << polydata->GetNumberOfPoints()
            << " points in the polydata." << std::endl;

  // Create 2 points in a vtkUnstructuredGrid

  vtkNew<vtkPoints> points;
  points->InsertNextPoint(0, 0, 0);
  points->InsertNextPoint(0, 0, 1);

  vtkNew<vtkUnstructuredGrid> ug;
  ug->SetPoints(points);

  std::cout << "There are " << ug->GetNumberOfPoints()
            << " points in the unstructured grid." << std::endl;

  // Combine the two data sets
  vtkNew<vtkAppendFilter> appendFilter;
  appendFilter->AddInputData(polydata);
  appendFilter->AddInputData(ug);
  appendFilter->Update();

  auto combined = appendFilter->GetOutput();
  std::cout << "There are " << combined->GetNumberOfPoints()
            << " points combined." << std::endl;

  // Create a mapper and actor
  vtkNew<vtkNamedColors> colors;

  vtkNew<vtkDataSetMapper> mapper;
  mapper->SetInputConnection(appendFilter->GetOutputPort());

  vtkNew<vtkActor> actor;
  actor->SetMapper(mapper);

  // Map the points to spheres
  auto sphereActor = PointToGlyph(appendFilter->GetOutput()->GetPoints(), 0.05);
  sphereActor->GetProperty()->SetColor(colors->GetColor3d("Gold").GetData());

  // Create a renderer, render window, and interactor
  vtkNew<vtkRenderer> renderer;
  vtkNew<vtkRenderWindow> renderWindow;
  renderWindow->AddRenderer(renderer);
  vtkNew<vtkRenderWindowInteractor> renderWindowInteractor;
  renderWindowInteractor->SetRenderWindow(renderWindow);

  // Add the actor to the scene
  renderer->AddActor(actor);
  renderer->AddActor(sphereActor);
  renderer->SetBackground(colors->GetColor3d("RoyalBlue").GetData());

  // Render and interact
  renderWindow->SetWindowName("AppendFilter");
  renderWindow->Render();
  renderWindowInteractor->Start();

  return EXIT_SUCCESS;
}

namespace {

vtkSmartPointer<vtkActor> PointToGlyph(vtkPoints* points, double const& scale)
{
  auto bounds = points->GetBounds();
  double maxLen = 0;
  for (int i = 1; i < 3; ++i)
  {
    maxLen = std::max(bounds[i + 1] - bounds[i], maxLen);
  }

  vtkNew<vtkSphereSource> sphereSource;
  sphereSource->SetRadius(scale * maxLen);

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

  vtkNew<vtkGlyph3DMapper> mapper;
  mapper->SetInputData(pd);
  mapper->SetSourceConnection(sphereSource->GetOutputPort());
  mapper->ScalarVisibilityOff();
  mapper->ScalingOff();

  vtkNew<vtkActor> actor;
  actor->SetMapper(mapper);

  return actor;
}

} // namespace```
###CMakeLists.txt
```cmake
cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

project(AppendFilter)

find_package(VTK COMPONENTS 
  vtkCommonColor
  vtkCommonCore
  vtkCommonDataModel
  vtkFiltersCore
  vtkFiltersSources
  vtkInteractionStyle
  vtkRenderingContextOpenGL2
  vtkRenderingCore
  vtkRenderingFreeType
  vtkRenderingGL2PSOpenGL2
  vtkRenderingOpenGL2
  QUIET
)

if (NOT VTK_FOUND)
  message("Skipping AppendFilter: ${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(AppendFilter MACOSX_BUNDLE AppendFilter.cxx )
  target_link_libraries(AppendFilter PRIVATE ${VTK_LIBRARIES})
else ()
  # include all components
  add_executable(AppendFilter MACOSX_BUNDLE AppendFilter.cxx )
  target_link_libraries(AppendFilter PRIVATE ${VTK_LIBRARIES})
  # vtk_module_autoinit is needed
  vtk_module_autoinit(
    TARGETS AppendFilter
    MODULES ${VTK_LIBRARIES}
    )
endif ()

Download and Build AppendFilter

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

cd AppendFilter/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:

./AppendFilter

WINDOWS USERS

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