RemoveOutsideSurface
VTKExamples/Cxx/PolyData/RemoveOutsideSurface
Description¶
This example removes the outer surface of a multiple surface vtkPolyData model. The examples assumes the outside surface is closed and there is only one outside surface. It also assumes that the center of the model lies inside the outer surface.
The example proceeds as follows:
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Use vtkConnectivityFilter to label all of the regions in the model with a region id.
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Cast a ray from outside the bounds of the model into the center of the model. Use a vtkCellLocator to intersect the ray with the model. The intersected cell will be on the outside surface of the model.
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The vtkCellData of the intersected cell will have the region id of the cell.
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Use a vtkCellIterator to visit each cell of the model. Cells whose region id is not equal to the interesected cell's region io are retained on a new vtkPolyData
The resulting vtkPolyData will contain all but the outside surface.
If run without arguments, the example generates several small (in area) spheres inside a large (in area) sphere. The inner sphere have more cells than the outer sphere, but will not be extracted.
The gold model is the original polydata and the blue model is the original with tghe outer surface removed.
You can try your own surface by specifying a XML PolyData file (.vtp) on the command line.
Seealso
ExtractOutsideSurface extracts only the outside surface.
Question
If you have a simple question about this example contact us at VTKExamplesProject If your question is more complex and may require extended discussion, please use the VTK Discourse Forum
Code¶
RemoveOutsideSurface.cxx
#include <vtkSmartPointer.h> #include <vtkConnectivityFilter.h> #include <vtkSphereSource.h> #include <vtkDataSetMapper.h> #include <vtkPolyDataMapper.h> #include <vtkActor.h> #include <vtkProperty.h> #include <vtkRenderer.h> #include <vtkRenderWindow.h> #include <vtkRenderWindowInteractor.h> #include <vtkAppendPolyData.h> #include <vtkCellLocator.h> #include <vtkXMLPolyDataReader.h> #include <vtkUnstructuredGrid.h> #include <vtkIdTypeArray.h> #include <vtkCellIterator.h> #include <vtkGenericCell.h> #include <vtkCellData.h> #include <vtkNamedColors.h> #include <vtkMath.h> int main(int argc, char *argv[]) { // PolyData to process vtkSmartPointer<vtkPolyData> polyData; if (argc > 1) { vtkSmartPointer<vtkXMLPolyDataReader> reader = vtkSmartPointer<vtkXMLPolyDataReader>::New(); reader->SetFileName(argv[1]); reader->Update(); polyData = reader->GetOutput(); } else { vtkMath::RandomSeed(5070); // for testing vtkSmartPointer<vtkAppendPolyData> appendFilter = vtkSmartPointer<vtkAppendPolyData>::New(); for (int i = 0; i < 20; ++i) { // Small spheres with most polgons vtkSmartPointer<vtkSphereSource> sphereSource1 = vtkSmartPointer<vtkSphereSource>::New(); sphereSource1->SetThetaResolution(10); sphereSource1->SetPhiResolution(10); sphereSource1->SetCenter(vtkMath::Random(4.0, 14.0), vtkMath::Random(-3.0, 5.0), vtkMath::Random(4.0, 14.0)); sphereSource1->SetRadius(1.0); appendFilter->AddInputConnection(sphereSource1->GetOutputPort()); } // Large sphere with least polygons vtkSmartPointer<vtkSphereSource> sphereSource2 = vtkSmartPointer<vtkSphereSource>::New(); sphereSource2->SetRadius(10); sphereSource2->SetCenter(10,1,10); appendFilter->AddInputConnection(sphereSource2->GetOutputPort()); appendFilter->Update(); polyData = appendFilter->GetOutput(); } double center[3], bounds[6]; polyData->GetCenter(center); std::cout << "Center of data: " << center[0] << ", " << center[1] << ", " << center[2] << std::endl; polyData->GetPoints()->GetBounds(bounds); std::cout << "Bounds of data: " << bounds[0] << ", " << bounds[1] << ", " << bounds[2] << ", " << bounds[3] << ", " << bounds[4] << ", " << bounds[5] << std::endl; // Extract all regions and label cells with region number vtkSmartPointer<vtkConnectivityFilter> connectivityFilter = vtkSmartPointer<vtkConnectivityFilter>::New(); connectivityFilter->SetInputData(polyData); connectivityFilter->SetExtractionModeToAllRegions(); connectivityFilter->ColorRegionsOn(); connectivityFilter->Update(); // Build a cell locator. vtkSmartPointer<vtkCellLocator> cellLocator = vtkSmartPointer<vtkCellLocator>::New(); cellLocator->SetDataSet(connectivityFilter->GetOutput()); cellLocator->BuildLocator(); // Now fire a ray from outside the bounds to the center and find a // cell. This cell should be on the outside surface double rayStart[3]; for (unsigned int i = 0; i < 3; i++) { rayStart[i] = bounds[2 * i + 1] * 1.1; } vtkIdType cellId = -1; double xyz[3], t, pcoords[3]; int subId; cellLocator->IntersectWithLine( rayStart, center, 0.0001, t, xyz, pcoords, subId, cellId); vtkIdTypeArray *cd = dynamic_cast<vtkIdTypeArray*>(connectivityFilter->GetOutput()->GetCellData()->GetScalars()); vtkIdType outsideRegionId = cd->GetTuple1(cellId); std::cout << "Id of cell on outside surface: " << cellId << std::endl; std::cout << "CellData at " << cellId << ": " << outsideRegionId << std::endl; // Build a polydata from cells that are not in the outside surface // Iterate over the original cells vtkSmartPointer<vtkPolyData> insidePolyData = vtkSmartPointer<vtkPolyData>::New(); insidePolyData->Allocate(); insidePolyData->SetPoints(connectivityFilter->GetOutput()->GetPoints()); vtkSmartPointer<vtkGenericCell> cell = vtkSmartPointer<vtkGenericCell>::New(); auto it = connectivityFilter->GetOutput()->NewCellIterator(); vtkIdType originalCellId = 0; for (it->InitTraversal(); !it->IsDoneWithTraversal(); it->GoToNextCell(), ++originalCellId) { // Retain cell if it is NOT an outside cell if (cd->GetTuple1(originalCellId) != outsideRegionId) { it->GetCell(cell); insidePolyData->InsertNextCell(it->GetCellType(), cell->GetPointIds()); } } it->Delete(); // Create a mapper and actor for original data vtkSmartPointer<vtkPolyDataMapper> originalMapper = vtkSmartPointer<vtkPolyDataMapper>::New(); originalMapper->SetInputData(polyData); vtkSmartPointer<vtkNamedColors> colors = vtkSmartPointer<vtkNamedColors>::New(); vtkSmartPointer<vtkActor> originalActor = vtkSmartPointer<vtkActor>::New(); originalActor->SetMapper(originalMapper); originalActor->GetProperty()->BackfaceCullingOn(); originalActor->GetProperty()->SetOpacity(.5);; originalActor->GetProperty()->SetColor(colors->GetColor3d("Gold").GetData()); // Create a mapper and actor for extracted data vtkSmartPointer<vtkPolyDataMapper> extractedMapper = vtkSmartPointer<vtkPolyDataMapper>::New(); extractedMapper->SetInputData(insidePolyData); vtkSmartPointer<vtkActor> extractedActor = vtkSmartPointer<vtkActor>::New(); extractedActor->GetProperty()->SetColor(colors->GetColor3d("Peacock").GetData()); extractedActor->SetMapper(extractedMapper); extractedActor->GetProperty()->SetOpacity(.5);; extractedActor->GetProperty()->BackfaceCullingOn(); // Create a renderer vtkSmartPointer<vtkRenderer> renderer = vtkSmartPointer<vtkRenderer>::New(); renderer->AddActor(originalActor); renderer->AddActor(extractedActor); renderer->GradientBackgroundOn(); renderer->SetBackground2(colors->GetColor3d("Beige").GetData()); renderer->SetBackground(colors->GetColor3d("Burlywood").GetData()); extractedActor->SetPosition((bounds[1] - bounds[0]) / 1.9, 0, 0); originalActor->SetPosition(-(bounds[1] - bounds[0]) / 1.9, 0, 0); // Create a render window vtkSmartPointer<vtkRenderWindow> renwin = vtkSmartPointer<vtkRenderWindow>::New(); renwin->AddRenderer(renderer); renwin->SetSize(512, 512); // Create an interactor vtkSmartPointer<vtkRenderWindowInteractor> iren = vtkSmartPointer<vtkRenderWindowInteractor>::New(); iren->SetRenderWindow(renwin); renwin->Render(); iren->Initialize(); iren->Start(); return EXIT_SUCCESS; }
CMakeLists.txt¶
cmake_minimum_required(VERSION 3.3 FATAL_ERROR) project(RemoveOutsideSurface) find_package(VTK COMPONENTS vtkCommonColor vtkCommonCore vtkCommonDataModel vtkFiltersCore vtkFiltersSources vtkIOXML vtkInteractionStyle vtkRenderingContextOpenGL2 vtkRenderingCore vtkRenderingFreeType vtkRenderingGL2PSOpenGL2 vtkRenderingOpenGL2 QUIET) if (NOT VTK_FOUND) message("Skipping RemoveOutsideSurface: ${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(RemoveOutsideSurface MACOSX_BUNDLE RemoveOutsideSurface.cxx ) target_link_libraries(RemoveOutsideSurface PRIVATE ${VTK_LIBRARIES}) else () # include all components add_executable(RemoveOutsideSurface MACOSX_BUNDLE RemoveOutsideSurface.cxx ) target_link_libraries(RemoveOutsideSurface PRIVATE ${VTK_LIBRARIES}) # vtk_module_autoinit is needed vtk_module_autoinit( TARGETS RemoveOutsideSurface MODULES ${VTK_LIBRARIES} ) endif ()
Download and Build RemoveOutsideSurface¶
Click here to download RemoveOutsideSurface and its CMakeLists.txt file. Once the tarball RemoveOutsideSurface.tar has been downloaded and extracted,
cd RemoveOutsideSurface/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:
./RemoveOutsideSurface
WINDOWS USERS
Be sure to add the VTK bin directory to your path. This will resolve the VTK dll's at run time.