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ClipFrustum

vtk-examples/Cxx/Meshes/ClipFrustum

Description

The example uses vtkClipPolyData to clip a model with a vtkCamera's view frustum. The frustum is displayed using vtkFrustumSource.

The example proceeds as follow:

  1. Read a vtkPolyData. The example can read any of the supported polydata readers.
  2. Generates a view of the model.
  3. Recovers the view frustum of the current vtkCamera.
  4. Creates an implicit function using vtkPlanes::SetFrustumPlanes.
  5. Passes the vtkPlanes to vtkFrustumSource.
  6. Passes the vtkPlanes to vtkClipPolyData as the ClipFunction.
  7. Tells vtkClipPolyData to generate vtkPolyData for inside and outside.
  8. Presents the frustum, and clipped models. The inside model is red and the outside model is gold.

Bug

The first attempt to write the example used vtkClipConvexPolyData, but that filter has bugs and only works with one plane.

Question

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

Code

ClipFrustum.cxx

#include <vtkClipPolyData.h>
#include <vtkFrustumSource.h>

#include <vtkNamedColors.h>
#include <vtkPlanes.h>
#include <vtkPolyDataNormals.h>

#include <vtkBYUReader.h>
#include <vtkOBJReader.h>
#include <vtkPLYReader.h>
#include <vtkPolyDataReader.h>
#include <vtkSTLReader.h>
#include <vtkSphereSource.h>
#include <vtkXMLPolyDataReader.h>

#include <vtksys/SystemTools.hxx>

#include <vtkActor.h>
#include <vtkCamera.h>
#include <vtkMapper.h>
#include <vtkNew.h>
#include <vtkPolyDataMapper.h>
#include <vtkProperty.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>
#include <vtkSmartPointer.h>

namespace {
vtkSmartPointer<vtkPolyData> ReadPolyData(const char* fileName);
void PositionCamera(vtkRenderer* renderer, double* viewUp,
                    double* position);
} // namespace

int main(int argc, char* argv[])
{
  auto polyData = ReadPolyData(argc > 1 ? argv[1] : "");

  vtkNew<vtkNamedColors> colors;

  // a renderer and render window
  vtkNew<vtkRenderer> renderer;
  vtkNew<vtkRenderWindow> renderWindow;
  renderWindow->AddRenderer(renderer);

  // an interactor
  vtkNew<vtkRenderWindowInteractor> renderWindowInteractor;
  renderWindowInteractor->SetRenderWindow(renderWindow);

  vtkNew<vtkPolyDataMapper> mapper;
  mapper->SetInputData(polyData);
  mapper->ScalarVisibilityOff();

  vtkNew<vtkActor> actor;
  actor->SetMapper(mapper);
  actor->GetProperty()->SetDiffuseColor(
      colors->GetColor3d("Crimson").GetData());
  actor->GetProperty()->SetSpecular(.6);
  actor->GetProperty()->SetSpecularPower(30);
  renderer->AddActor(actor);

  vtkNew<vtkPolyDataMapper> outMapper;
  outMapper->SetInputData(polyData);
  outMapper->ScalarVisibilityOff();

  vtkNew<vtkActor> outActor;
  outActor->SetMapper(outMapper);
  outActor->GetProperty()->SetDiffuseColor(
      colors->GetColor3d("Gold").GetData());
  outActor->GetProperty()->SetSpecular(.6);
  outActor->GetProperty()->SetSpecularPower(30);

  // Position the camera so that we can see the frustum
  double viewUp[3] = {0.0, 1.0, 0.0};
  double position[3] = {1.0, 0.0, 0.0};
  PositionCamera(renderer, viewUp, position);
  renderer->GetActiveCamera()->Elevation(30);
  renderer->GetActiveCamera()->SetViewAngle(10.0);

  double planesArray[24];
  renderer->GetActiveCamera()->GetFrustumPlanes(1.0, planesArray);

  vtkNew<vtkPlanes> planes;
  planes->SetFrustumPlanes(planesArray);

  vtkNew<vtkFrustumSource> frustumSource;
  frustumSource->ShowLinesOff();
  frustumSource->SetPlanes(planes);
  frustumSource->Update();

  vtkNew<vtkPolyDataMapper> frustumMapper;
  frustumMapper->SetInputConnection(frustumSource->GetOutputPort());

  vtkNew<vtkActor> frustumActor;
  frustumActor->SetMapper(frustumMapper);
  frustumActor->GetProperty()->EdgeVisibilityOn();
  frustumActor->GetProperty()->SetOpacity(.5);
  frustumActor->GetProperty()->SetColor(colors->GetColor3d("Banana").GetData());

  vtkNew<vtkClipPolyData> clip;
  clip->SetInputData(polyData);
  clip->SetClipFunction(planes);
  clip->InsideOutOn();
  clip->GenerateClippedOutputOn();
  clip->Update();

  mapper->SetInputConnection(clip->GetOutputPort());
  outMapper->SetInputData(clip->GetClippedOutput());

  renderer->SetBackground(colors->GetColor3d("Silver").GetData());
  renderer->AddActor(frustumActor);
  renderer->AddActor(outActor);

  renderer->ResetCamera();
  renderer->GetActiveCamera()->Azimuth(30);
  renderer->GetActiveCamera()->Elevation(30);
  renderer->GetActiveCamera()->Dolly(1.5);
  renderer->ResetCameraClippingRange();

  renderWindow->SetSize(640, 480);
  renderWindow->SetWindowName("ClipFrustum");

  renderWindow->Render();

  // begin mouse interaction
  renderWindowInteractor->Start();

  return EXIT_SUCCESS;
}

// Snippets
namespace {
vtkSmartPointer<vtkPolyData> ReadPolyData(const char* fileName)
{
  vtkSmartPointer<vtkPolyData> polyData;
  std::string extension =
      vtksys::SystemTools::GetFilenameExtension(std::string(fileName));
  if (extension == ".ply")
  {
    vtkNew<vtkPLYReader> reader;
    reader->SetFileName(fileName);
    reader->Update();
    polyData = reader->GetOutput();
  }
  else if (extension == ".vtp")
  {
    vtkNew<vtkXMLPolyDataReader> reader;
    reader->SetFileName(fileName);
    reader->Update();
    polyData = reader->GetOutput();
  }
  else if (extension == ".obj")
  {
    vtkNew<vtkOBJReader> reader;
    reader->SetFileName(fileName);
    reader->Update();
    polyData = reader->GetOutput();
  }
  else if (extension == ".stl")
  {
    vtkNew<vtkSTLReader> reader;
    reader->SetFileName(fileName);
    reader->Update();
    polyData = reader->GetOutput();
  }
  else if (extension == ".vtk")
  {
    vtkNew<vtkPolyDataReader> reader;
    reader->SetFileName(fileName);
    reader->Update();
    polyData = reader->GetOutput();
  }
  else if (extension == ".g")
  {
    vtkNew<vtkBYUReader> reader;
    reader->SetGeometryFileName(fileName);
    reader->Update();
    polyData = reader->GetOutput();
  }
  else
  {
    vtkNew<vtkSphereSource> source;
    source->Update();
    polyData = source->GetOutput();
  }
  return polyData;
}

void PositionCamera(vtkRenderer* renderer, double* viewUp, double* position)
{
  renderer->GetActiveCamera()->SetFocalPoint(0.0, 0.0, 0.0);
  renderer->GetActiveCamera()->SetViewUp(viewUp);
  renderer->GetActiveCamera()->SetPosition(position);
  renderer->ResetCamera();
  return;
}
} // namespace

CMakeLists.txt

cmake_minimum_required(VERSION 3.12 FATAL_ERROR)

project(ClipFrustum)

find_package(VTK COMPONENTS 
  CommonColor
  CommonCore
  CommonDataModel
  FiltersCore
  FiltersSources
  IOGeometry
  IOLegacy
  IOPLY
  IOXML
  InteractionStyle
  RenderingContextOpenGL2
  RenderingCore
  RenderingFreeType
  RenderingGL2PSOpenGL2
  RenderingOpenGL2
  QUIET
)

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

Download and Build ClipFrustum

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

cd ClipFrustum/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:

./ClipFrustum

WINDOWS USERS

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