ExtractOutsideSurface
VTKExamples/Cxx/PolyData/ExtractOutsideSurface
Description
This example extracts the outer surface of a multiple surface polydata 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 casts a ray from outside the bounds of the model into the center of the model. It uses a vtkCellLocator to intersect the ray with the model. The intersected cell is used as a seed to the vtkPolyDataConnectivityFilter which is run with the extraction mode set to CellSeededRegions.
If run without arguments, the example generates a small (in area) sphere inside a large (in area) sphere. The inner sphere has more cells than the outer sphere, but should not be extracted.
You can try your own surface by specifying a XML PolyData file (.vtp) on the command line.
Code
ExtractOutsideSurface.cxx
#include <vtkVersion.h>
#include <vtkSmartPointer.h>
#include <vtkSphereSource.h>
#include <vtkPolyDataConnectivityFilter.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 <vtkTriangleFilter.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
{
// Small sphere with most polgons
vtkSmartPointer<vtkSphereSource> sphereSource1 =
vtkSmartPointer<vtkSphereSource>::New();
sphereSource1->SetThetaResolution(10);
sphereSource1->SetPhiResolution(10);
sphereSource1->SetCenter(5, 5, 5);
// Large sphere with least polygons
vtkSmartPointer<vtkSphereSource> sphereSource2 =
vtkSmartPointer<vtkSphereSource>::New();
sphereSource2->SetRadius(10);
sphereSource2->SetCenter(10,1,10);
vtkSmartPointer<vtkAppendPolyData> appendFilter =
vtkSmartPointer<vtkAppendPolyData>::New();
appendFilter->AddInputConnection(sphereSource1->GetOutputPort());
appendFilter->AddInputConnection(sphereSource2->GetOutputPort());
appendFilter->Update();
polyData = appendFilter->GetOutput();
}
double center[3], bounds[6];
polyData->GetCenter(center);
std::cout << "Center of data is: "
<< center[0] << ", "
<< center[1] << ", "
<< center[2] << std::endl;
polyData->GetPoints()->GetBounds(bounds);
std::cout << "Bounds of data is: "
<< bounds[0] << ", "
<< bounds[1] << ", "
<< bounds[2] << ", "
<< bounds[3] << ", "
<< bounds[4] << ", "
<< bounds[5] << std::endl;
// Build a cell locator.
vtkSmartPointer<vtkCellLocator> cellLocator =
vtkSmartPointer<vtkCellLocator>::New();
cellLocator->SetDataSet(polyData);
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);
std::cout << "Id of cell on outside surface: " << cellId << std::endl;
vtkSmartPointer<vtkPolyDataConnectivityFilter> connectivityFilter =
vtkSmartPointer<vtkPolyDataConnectivityFilter>::New();
#if VTK_MAJOR_VERSION <= 5
connectivityFilter->SetInput(polyData);
#else
connectivityFilter->SetInputData(polyData);
#endif
connectivityFilter->SetExtractionModeToCellSeededRegions();
connectivityFilter->InitializeSeedList();
connectivityFilter->AddSeed(cellId);
// Create a mapper and actor for original data
vtkSmartPointer<vtkPolyDataMapper> originalMapper =
vtkSmartPointer<vtkPolyDataMapper>::New();
#if VTK_MAJOR_VERSION <= 5
originalMapper->SetInput(polyData);
#else
originalMapper->SetInputData(polyData);
#endif
vtkSmartPointer<vtkActor> originalActor =
vtkSmartPointer<vtkActor>::New();
originalActor->SetMapper(originalMapper);
// Create a mapper and actor for extracted data
vtkSmartPointer<vtkPolyDataMapper> extractedMapper =
vtkSmartPointer<vtkPolyDataMapper>::New();
extractedMapper->SetInputConnection(connectivityFilter->GetOutputPort());
vtkSmartPointer<vtkActor> extractedActor =
vtkSmartPointer<vtkActor>::New();
extractedActor->GetProperty()->SetColor(1,0,0);
extractedActor->SetMapper(extractedMapper);
// Create a renderer
vtkSmartPointer<vtkRenderer> renderer =
vtkSmartPointer<vtkRenderer>::New();
renderer->AddActor(originalActor);
renderer->AddActor(extractedActor);
// Create a render window
vtkSmartPointer<vtkRenderWindow> renwin =
vtkSmartPointer<vtkRenderWindow>::New();
renwin->AddRenderer(renderer);
// Create an interactor
vtkSmartPointer<vtkRenderWindowInteractor> iren =
vtkSmartPointer<vtkRenderWindowInteractor>::New();
iren->SetRenderWindow(renwin);
iren->Initialize();
iren->Start();
return EXIT_SUCCESS;
}
CMakeLists.txt
cmake_minimum_required(VERSION 2.8)
PROJECT(ExtractOutsideSurface)
find_package(VTK REQUIRED)
include(${VTK_USE_FILE})
add_executable(ExtractOutsideSurface MACOSX_BUNDLE ExtractOutsideSurface.cxx)
target_link_libraries(ExtractOutsideSurface ${VTK_LIBRARIES})
Download and Build ExtractOutsideSurface
Click here to download ExtractOutsideSurface and its CMakeLists.txt file. Once the tarball ExtractOutsideSurface.tar has been downloaded and extracted,
cd ExtractOutsideSurface/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:
./ExtractOutsideSurface
WINDOWS USERS PLEASE NOTE: Be sure to add the VTK bin directory to your path. This will resolve the VTK dll's at run time.