Skip to content

CapClip

vtk-examples/Cxx/Meshes/CapClip


Description

This example shows how to generate a "cap" on a clipped vtkPolyData. After clipping with vtkClipPolyData, it uses a clever ''trick'' to convert polylines into polygons. If a polydata file is provided, it will cap it. Otherwise it caps a clipped sphere.

Warning

The clipping is done with a scalar field provided by vtkPlane and results may depend on the resolution of the input vtkPolyData.

Style

This example collects all of the color definition in the beginning of the example. This makes it easier to make changes to the colors without having to search the code.

Other languages

See (Python), (CSharp)

Question

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

Code

CapClip.cxx

#include <vtkActor.h>
#include <vtkCamera.h>
#include <vtkClipPolyData.h>
#include <vtkDataSetMapper.h>
#include <vtkFeatureEdges.h>
#include <vtkNamedColors.h>
#include <vtkNew.h>
#include <vtkPlane.h>
#include <vtkPolyData.h>
#include <vtkPolyDataMapper.h>
#include <vtkProperty.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>
#include <vtkSmartPointer.h>
#include <vtkSphereSource.h>
#include <vtkStripper.h>
#include <vtkXMLPolyDataReader.h>

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

namespace {
vtkSmartPointer<vtkPolyData> ReadPolyData(std::string const& fileName);
}

//
// Demonstrate the use of clipping and capping on polyhedral data
//

int main(int argc, char* argv[])
{
  // Define colors
  vtkNew<vtkNamedColors> colors;
  auto backgroundColor = colors->GetColor3d("steel_blue");
  auto boundaryColor = colors->GetColor3d("banana");
  auto clipColor = colors->GetColor3d("tomato");
  // PolyData to process
  auto polyData = ReadPolyData(argc > 1 ? argv[1] : "");

  vtkNew<vtkPlane> plane;
  plane->SetOrigin(polyData->GetCenter());
  plane->SetNormal(1.0, -1.0, -1.0);

  vtkNew<vtkClipPolyData> clipper;
  clipper->SetInputData(polyData);
  clipper->SetClipFunction(plane);
  clipper->SetValue(0);
  clipper->Update();

  polyData = clipper->GetOutput();

  vtkNew<vtkDataSetMapper> clipMapper;
  clipMapper->SetInputData(polyData);

  vtkNew<vtkActor> clipActor;
  clipActor->SetMapper(clipMapper);
  clipActor->GetProperty()->SetDiffuseColor(clipColor.GetData());
  clipActor->GetProperty()->SetInterpolationToFlat();
  clipActor->GetProperty()->EdgeVisibilityOn();

  // Now extract feature edges
  vtkNew<vtkFeatureEdges> boundaryEdges;
  boundaryEdges->SetInputData(polyData);
  boundaryEdges->BoundaryEdgesOn();
  boundaryEdges->FeatureEdgesOff();
  boundaryEdges->NonManifoldEdgesOff();
  boundaryEdges->ManifoldEdgesOff();

  vtkNew<vtkStripper> boundaryStrips;
  boundaryStrips->SetInputConnection(boundaryEdges->GetOutputPort());
  boundaryStrips->Update();

  // Change the polylines into polygons
  vtkNew<vtkPolyData> boundaryPoly;
  boundaryPoly->SetPoints(boundaryStrips->GetOutput()->GetPoints());
  boundaryPoly->SetPolys(boundaryStrips->GetOutput()->GetLines());

  vtkNew<vtkPolyDataMapper> boundaryMapper;
  boundaryMapper->SetInputData(boundaryPoly);

  vtkNew<vtkActor> boundaryActor;
  boundaryActor->SetMapper(boundaryMapper);
  boundaryActor->GetProperty()->SetDiffuseColor(boundaryColor.GetData());

  // Create graphics stuff
  //
  vtkNew<vtkRenderer> renderer;
  renderer->SetBackground(backgroundColor.GetData());
  renderer->UseHiddenLineRemovalOn();

  vtkNew<vtkRenderWindow> renderWindow;
  renderWindow->AddRenderer(renderer);
  renderWindow->SetSize(640, 480);

  vtkNew<vtkRenderWindowInteractor> interactor;
  interactor->SetRenderWindow(renderWindow);

  // Add the actors to the renderer, set the background and size
  //
  renderer->AddActor(clipActor);
  renderer->AddActor(boundaryActor);

  // Generate an interesting view
  //
  renderer->ResetCamera();
  renderer->GetActiveCamera()->Azimuth(30);
  renderer->GetActiveCamera()->Elevation(30);
  renderer->GetActiveCamera()->Dolly(1.2);
  renderer->ResetCameraClippingRange();

  renderWindow->Render();
  renderWindow->SetWindowName("CapClip");
  renderWindow->Render();

  interactor->Start();

  return EXIT_SUCCESS;
}

namespace {
vtkSmartPointer<vtkPolyData> ReadPolyData(std::string const& fileName)
{
  vtkSmartPointer<vtkPolyData> polyData;
  std::string extension = "";
  if (fileName.find_last_of(".") != std::string::npos)
  {
    extension = fileName.substr(fileName.find_last_of("."));
  }
  // Make the extension lowercase
  std::transform(extension.begin(), extension.end(), extension.begin(),
                 ::tolower);
  if (extension == ".ply")
  {
    vtkNew<vtkPLYReader> reader;
    reader->SetFileName(fileName.c_str());
    reader->Update();
    polyData = reader->GetOutput();
  }
  else if (extension == ".vtp")
  {
    vtkNew<vtkXMLPolyDataReader> reader;
    reader->SetFileName(fileName.c_str());
    reader->Update();
    polyData = reader->GetOutput();
  }
  else if (extension == ".obj")
  {
    vtkNew<vtkOBJReader> reader;
    reader->SetFileName(fileName.c_str());
    reader->Update();
    polyData = reader->GetOutput();
  }
  else if (extension == ".stl")
  {
    vtkNew<vtkSTLReader> reader;
    reader->SetFileName(fileName.c_str());
    reader->Update();
    polyData = reader->GetOutput();
  }
  else if (extension == ".vtk")
  {
    vtkNew<vtkPolyDataReader> reader;
    reader->SetFileName(fileName.c_str());
    reader->Update();
    polyData = reader->GetOutput();
  }
  else if (extension == ".g")
  {
    vtkNew<vtkBYUReader> reader;
    reader->SetGeometryFileName(fileName.c_str());
    reader->Update();
    polyData = reader->GetOutput();
  }
  else
  {
    // Return a polydata sphere if the extension is unknown.
    vtkNew<vtkSphereSource> source;
    source->SetThetaResolution(20);
    source->SetPhiResolution(11);
    source->Update();
    polyData = source->GetOutput();
  }
  return polyData;
}
} // namespace

CMakeLists.txt

cmake_minimum_required(VERSION 3.12 FATAL_ERROR)

project(CapClip)

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 "CapClip: 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(CapClip MACOSX_BUNDLE CapClip.cxx )
  target_link_libraries(CapClip PRIVATE ${VTK_LIBRARIES}
)
# vtk_module_autoinit is needed
vtk_module_autoinit(
  TARGETS CapClip
  MODULES ${VTK_LIBRARIES}
)

Download and Build CapClip

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

cd CapClip/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:

./CapClip

WINDOWS USERS

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