Subdivision
VTKExamples/Cxx/Meshes/Subdivision
Description
In this example a mesh is read from a file and then subdivided using linear subdivision. The SetNumberOfSubdivisions(n) function controls how many times the mesh is subdivided. For each n, the number of triangles will increase by approximately a factor of 4. For example, if n=2, the number of triangles in the resulting mesh will be 16x the number of triangles in the original mesh.
Different types of subdivisions can be obtained by replacing vtkLinearSubdivisionFilter with either vtkLoopSubdivisionFilter or vtkButterflySubdivisionFilter.
Code
Subdivision.cxx
#include <vtkVersion.h>
#include <vtkSmartPointer.h>
#include <vtkCellData.h>
#include <vtkCellArray.h>
#include <vtkDoubleArray.h>
#include <vtkPoints.h>
#include <vtkTriangle.h>
#include <vtkPolyData.h>
#include <vtkPointData.h>
#include <vtkSphereSource.h>
#include <vtkXMLPolyDataReader.h>
#include <vtkTriangleFilter.h>
#include <vtkPolyDataMapper.h>
#include <vtkActor.h>
#include <vtkRenderWindow.h>
#include <vtkRenderer.h>
#include <vtkRenderWindowInteractor.h>
#include <string>
#include <vtkButterflySubdivisionFilter.h>
#include <vtkLoopSubdivisionFilter.h>
#include <vtkLinearSubdivisionFilter.h>
int main(int argc, char *argv[])
{
vtkSmartPointer<vtkPolyData> originalMesh;
if(argc > 1) //If a file name is specified, open and use the file.
{
vtkSmartPointer<vtkXMLPolyDataReader> reader =
vtkSmartPointer<vtkXMLPolyDataReader>::New();
reader->SetFileName(argv[1]);
// Subdivision filters only work on triangles
vtkSmartPointer<vtkTriangleFilter> triangles =
vtkSmartPointer<vtkTriangleFilter>::New();
triangles->SetInputConnection(reader->GetOutputPort());
triangles->Update();
originalMesh = triangles->GetOutput();
}
else //If a file name is not specified, create a sphere
{
vtkSmartPointer<vtkSphereSource> sphereSource =
vtkSmartPointer<vtkSphereSource>::New();
sphereSource->Update();
originalMesh = sphereSource->GetOutput();
}
std::cout << "Before subdivision" << std::endl;
std::cout << " There are " << originalMesh->GetNumberOfPoints()
<< " points." << std::endl;
std::cout << " There are " << originalMesh->GetNumberOfPolys()
<< " triangles." << std::endl;
double numberOfViewports = 3.;
vtkSmartPointer<vtkRenderWindow> renderWindow =
vtkSmartPointer<vtkRenderWindow>::New();
renderWindow->SetSize(200* numberOfViewports,200); //(width, height)
vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor =
vtkSmartPointer<vtkRenderWindowInteractor>::New();
renderWindowInteractor->SetRenderWindow(renderWindow);
int numberOfSubdivisions = 2;
for(unsigned i = 0; i < numberOfViewports; i++)
{
// Note: Here we create a superclass pointer (vtkPolyDataAlgorithm) so that we can easily instantiate different
// types of subdivision filters. Typically you would not want to do this, but rather create the pointer to be the type
// filter you will actually use, e.g.
// vtkSmartPointer<vtkLinearSubdivisionFilter> subdivisionFilter = vtkSmartPointer<vtkLinearSubdivisionFilter>::New();
vtkSmartPointer<vtkPolyDataAlgorithm> subdivisionFilter;
switch(i)
{
case 0:
subdivisionFilter = vtkSmartPointer<vtkLinearSubdivisionFilter>::New();
dynamic_cast<vtkLinearSubdivisionFilter *> (subdivisionFilter.GetPointer())->SetNumberOfSubdivisions(numberOfSubdivisions);
break;
case 1:
subdivisionFilter = vtkSmartPointer<vtkLoopSubdivisionFilter>::New();
dynamic_cast<vtkLoopSubdivisionFilter *> (subdivisionFilter.GetPointer())->SetNumberOfSubdivisions(numberOfSubdivisions);
break;
case 2:
subdivisionFilter = vtkSmartPointer<vtkButterflySubdivisionFilter>::New();
dynamic_cast<vtkButterflySubdivisionFilter *> (subdivisionFilter.GetPointer())->SetNumberOfSubdivisions(numberOfSubdivisions);
break;
default:
break;
}
#if VTK_MAJOR_VERSION <= 5
subdivisionFilter->SetInputConnection(originalMesh->GetProducerPort());
#else
subdivisionFilter->SetInputData(originalMesh);
#endif
subdivisionFilter->Update();
vtkSmartPointer<vtkRenderer> renderer =
vtkSmartPointer<vtkRenderer>::New();
renderWindow->AddRenderer(renderer);
renderer->SetViewport(static_cast<double>(i)/numberOfViewports,0,static_cast<double>(i+1)/numberOfViewports,1);
//Create a mapper and actor
vtkSmartPointer<vtkPolyDataMapper> mapper =
vtkSmartPointer<vtkPolyDataMapper>::New();
mapper->SetInputConnection(subdivisionFilter->GetOutputPort());
vtkSmartPointer<vtkActor> actor = vtkSmartPointer<vtkActor>::New();
actor->SetMapper(mapper);
renderer->AddActor(actor);
renderer->ResetCamera();
renderWindow->Render();
renderWindow->SetWindowName("Multiple ViewPorts");
}
renderWindowInteractor->Start();
return EXIT_SUCCESS;
}
CMakeLists.txt
cmake_minimum_required(VERSION 2.8)
PROJECT(Subdivision)
find_package(VTK REQUIRED)
include(${VTK_USE_FILE})
add_executable(Subdivision MACOSX_BUNDLE Subdivision.cxx)
target_link_libraries(Subdivision ${VTK_LIBRARIES})
Download and Build Subdivision
Click here to download Subdivision and its CMakeLists.txt file. Once the tarball Subdivision.tar has been downloaded and extracted,
cd Subdivision/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:
./Subdivision
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.