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PolyhedronAndHexahedron

Repository source: PolyhedronAndHexahedron

Description

This is a demonstration of how to construct an unstructured grid containing mixed cells types, polyhedron and hexahedron. It rely on the SetPolyhedralCells API. The resulting object is then displayed.

Other languages

See (Python)

Question

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

Code

PolyhedronAndHexahedron.cxx

#include <vtkActor.h>
#include <vtkCamera.h>
#include <vtkDataSetMapper.h>
#include <vtkIdList.h>
#include <vtkNamedColors.h>
#include <vtkNew.h>
#include <vtkPoints.h>
#include <vtkProperty.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>
#include <vtkUnstructuredGrid.h>
#include <vtkXMLUnstructuredGridWriter.h>

int main(int, char*[])
{
  vtkNew<vtkNamedColors> colors;

  // create polyhedron (cube)

  // Create points in an arbitrary order
  vtkNew<vtkPoints> points;
  points->InsertNextPoint(-5.0, -5.0, -10.0);
  points->InsertNextPoint(-5.0, -5.0, 10.0);
  points->InsertNextPoint(-5.0, 5.0, -10.0);
  points->InsertNextPoint(-5.0, 5.0, 10.0);
  points->InsertNextPoint(5.0, -5.0, -10.0);
  points->InsertNextPoint(5.0, -5.0, 10.0);
  points->InsertNextPoint(5.0, 5.0, -10.0);
  points->InsertNextPoint(5.0, 5.0, 10.0);

  // The ID of the points that compose the polyhedron cell
  vtkIdType pointIds[8] = {0, 1, 2, 3, 4, 5, 6, 7};

  // The ID of the points that compose each individual faces
  vtkNew<vtkCellArray> faces;
  vtkIdType face0[4] = { 0, 2, 6, 4 };
  vtkIdType face1[4] = { 1, 3, 7, 5 };
  vtkIdType face2[4] = { 0, 1, 3, 2 };
  vtkIdType face3[4] = { 4, 5, 7, 6 };
  vtkIdType face4[4] = { 0, 1, 5, 4 };
  vtkIdType face5[4] = { 2, 3, 7, 6 };

  // Insert each face
  faces->InsertNextCell(4, face0);
  faces->InsertNextCell(4, face1);
  faces->InsertNextCell(4, face2);
  faces->InsertNextCell(4, face3);
  faces->InsertNextCell(4, face4);
  faces->InsertNextCell(4, face5);

  // Add the IDs of the faces for the polyhedron cell
  vtkNew<vtkCellArray> faceLocations;
  vtkIdType faceIds[6] = { 0, 1, 2, 3, 4, 5 };
  faceLocations->InsertNextCell(6, faceIds);

  // Insert the polyhedron cell   
  vtkNew<vtkCellArray> cells;
  cells->InsertNextCell(8, pointIds);

  // Insert the type of the cell
  vtkNew<vtkUnsignedCharArray> cellTypes;
  cellTypes->InsertNextValue(VTK_POLYHEDRON);

  // Create hexahedron 

  // Create points in hexahedron order
  points->InsertNextPoint(-5.0, -5.0, 15.0);
  points->InsertNextPoint(5.0, -5.0, 15.0);
  points->InsertNextPoint(5.0, 5.0, 15.0);
  points->InsertNextPoint(-5.0, 5.0, 15.0);
  points->InsertNextPoint(-5.0, -5.0, 35.0);
  points->InsertNextPoint(5.0, -5.0, 35.0);
  points->InsertNextPoint(5.0, 5.0, 35.0);
  points->InsertNextPoint(-5.0, 5.0, 35.0);

  // The ID of the points of the hexahedron
  vtkIdType pointIdsh[8] = { 8, 9, 10, 11, 12, 13, 14, 15 };

  // Add the ID of the "faces" for the hexahedon, its empty because hexahedron does not need faces
  // But we still need faceLocations to have the same size as the number of cells
  faceLocations->InsertNextCell(0);

  // Insert the hexahedron
  cells->InsertNextCell(8, pointIdsh);

  // Insert the cell type
  cellTypes->InsertNextValue(VTK_HEXAHEDRON);

  // Set points and polyhedral cells
  vtkNew<vtkUnstructuredGrid> ugrid0;
  ugrid0->SetPoints(points);
  ugrid0->SetPolyhedralCells(cellTypes, cells, faceLocations, faces);

  // Create a mapper and actor
  vtkNew<vtkDataSetMapper> mapper;
  mapper->SetInputData(ugrid0);

  vtkNew<vtkActor> actor;
  actor->SetMapper(mapper);
  actor->GetProperty()->SetColor(colors->GetColor3d("Silver").GetData());

  // Visualize.
  vtkNew<vtkRenderer> renderer;
  vtkNew<vtkRenderWindow> renderWindow;
  renderWindow->SetWindowName("Polyhedron");
  renderWindow->AddRenderer(renderer);
  vtkNew<vtkRenderWindowInteractor> renderWindowInteractor;
  renderWindowInteractor->SetRenderWindow(renderWindow);

  renderer->AddActor(actor);
  renderer->SetBackground(colors->GetColor3d("Salmon").GetData());
  renderer->ResetCamera();
  renderer->GetActiveCamera()->Azimuth(30);
  renderer->GetActiveCamera()->Elevation(30);
  renderWindow->Render();
  renderWindowInteractor->Start();

  return EXIT_SUCCESS;
}

CMakeLists.txt

cmake_minimum_required(VERSION 3.12 FATAL_ERROR)

project(PolyhedronAndHexahedron)

find_package(VTK COMPONENTS 
  CommonColor
  CommonCore
  CommonDataModel
  IOXML
  InteractionStyle
  RenderingContextOpenGL2
  RenderingCore
  RenderingFreeType
  RenderingGL2PSOpenGL2
  RenderingOpenGL2
)

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

Download and Build PolyhedronAndHexahedron

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

cd PolyhedronAndHexahedron/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:

./PolyhedronAndHexahedron

WINDOWS USERS

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