# DiscreteMarchingCubes

VTKExamples/Cxx/Modelling/DiscreteMarchingCubes

### Description¶

Creates surfaces from labelled data. Volume data does not always contain samples of continuous data. A volume may contain discrete integer values, often the result of segmentation. vtkDiscreteMarchingCubes creates surfaces from these segmented volumes using a modified marching cubes algorithm. The algorithm generates one or more models representing the boundaries between the specified label and the adjacent structures. One or more label values must be specified to generate the models. The boundary positions are always defined to be half-way between adjacent voxels.

Seealso

SmoothDiscreteMarchingCubes produces smooth models.

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¶

DiscreteMarchingCubes.cxx

#include <vtkSmartPointer.h>
#include <vtkDiscreteMarchingCubes.h>

#include <vtkMath.h>
#include <vtkImageData.h>
#include <vtkSphere.h>
#include <vtkSampleFunction.h>
#include <vtkImageThreshold.h>
#include <vtkImageMathematics.h>
#include <vtkPolyDataMapper.h>

#include <vtkRenderer.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkActor.h>
#include <vtkLookupTable.h>

#include <vtkNamedColors.h>

static vtkSmartPointer<vtkLookupTable> MakeColors (unsigned int n);
static vtkSmartPointer<vtkImageData> MakeBlob(int n, double radius);

int main (int /*argc*/, char * /* argv */ [])
{
int n = 20;
double radius = 8;

vtkSmartPointer<vtkImageData> blob = MakeBlob(n, radius);

vtkSmartPointer<vtkDiscreteMarchingCubes> discrete =
vtkSmartPointer<vtkDiscreteMarchingCubes>::New();
discrete->SetInputData(blob);
discrete->GenerateValues(n, 1, n);

vtkSmartPointer<vtkLookupTable> lut = MakeColors(n);

vtkSmartPointer<vtkPolyDataMapper> mapper =
vtkSmartPointer<vtkPolyDataMapper>::New();
mapper->SetInputConnection(discrete->GetOutputPort());
mapper->SetLookupTable(lut);
mapper->SetScalarRange(0, lut->GetNumberOfColors());

// Create the RenderWindow, Renderer and both Actors
//
vtkSmartPointer<vtkRenderer> ren1 =
vtkSmartPointer<vtkRenderer>::New();
vtkSmartPointer<vtkRenderWindow> renWin =
vtkSmartPointer<vtkRenderWindow>::New();
vtkSmartPointer<vtkRenderWindowInteractor> iren =
vtkSmartPointer<vtkRenderWindowInteractor>::New();
iren->SetRenderWindow(renWin);

vtkSmartPointer<vtkActor> actor =
vtkSmartPointer<vtkActor>::New();
actor->SetMapper(mapper);

vtkSmartPointer<vtkNamedColors> colors =
vtkSmartPointer<vtkNamedColors>::New();
ren1->SetBackground(colors->GetColor3d("Burlywood").GetData());

renWin->Render();

iren->Start();

return EXIT_SUCCESS;
}

vtkSmartPointer<vtkImageData> MakeBlob(int n, double radius)
{
vtkSmartPointer<vtkMath> math =
vtkSmartPointer<vtkMath>::New();

vtkSmartPointer<vtkImageData> blobImage =
vtkSmartPointer<vtkImageData>::New();

for (int i = 0; i < n; ++i)
{
vtkSmartPointer<vtkSphere> sphere =
vtkSmartPointer<vtkSphere>::New();
double maxR = 50 - 2.0 * radius;
sphere->SetCenter(int(math->Random(-maxR, maxR)),
int(math->Random(-maxR, maxR)), int(math->Random(-maxR, maxR)));

vtkSmartPointer<vtkSampleFunction> sampler =
vtkSmartPointer<vtkSampleFunction>::New();
sampler->SetImplicitFunction(sphere);
sampler->SetOutputScalarTypeToFloat();
sampler->SetSampleDimensions(100, 100, 100);
sampler->SetModelBounds(-50, 50, -50, 50, -50, 50);

vtkSmartPointer<vtkImageThreshold> thres =
vtkSmartPointer<vtkImageThreshold>::New();
thres->SetInputConnection(sampler->GetOutputPort());
thres->ReplaceInOn();
thres->ReplaceOutOn();
thres->SetInValue(i + 1);
thres->SetOutValue(0);
thres->Update();
if (i == 0)
{
blobImage->DeepCopy(thres->GetOutput());
}

vtkSmartPointer<vtkImageMathematics>     maxValue =
vtkSmartPointer<vtkImageMathematics>::New();
maxValue->SetInputData(0, blobImage);
maxValue->SetInputData(1, thres->GetOutput());
maxValue->SetOperationToMax();
maxValue->Modified();
maxValue->Update();

blobImage->DeepCopy(maxValue->GetOutput());
}
return blobImage;
}

// Generate some random colors
vtkSmartPointer<vtkLookupTable> MakeColors (unsigned int n)
{
vtkSmartPointer<vtkLookupTable> lut =
vtkSmartPointer<vtkLookupTable>::New();
lut->SetNumberOfColors(n);
lut->SetTableRange(0, n - 1);
lut->SetScaleToLinear();
lut->Build();
lut->SetTableValue(0, 0, 0, 0, 1);

vtkSmartPointer<vtkMath> math =
vtkSmartPointer<vtkMath>::New();
math->RandomSeed(5071);
for ( int i = 1; i < static_cast<int>(n); ++i)
{
lut->SetTableValue(i, math->Random(.4, 1),
math->Random(.4, 1), math->Random(.4, 1), 1.0);
}
return lut;
}


### CMakeLists.txt¶

cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

project(DiscreteMarchingCubes)

find_package(VTK COMPONENTS
vtkCommonColor
vtkCommonCore
vtkCommonDataModel
vtkFiltersGeneral
vtkImagingCore
vtkImagingHybrid
vtkImagingMath
vtkInteractionStyle
vtkRenderingCore
vtkRenderingFreeType
vtkRenderingOpenGL2 QUIET)
if (NOT VTK_FOUND)
message("Skipping DiscreteMarchingCubes: ${VTK_NOT_FOUND_MESSAGE}") return () endif() message (STATUS "VTK_VERSION:${VTK_VERSION}")
if (VTK_VERSION VERSION_LESS "8.90.0")
# old system
include(${VTK_USE_FILE}) add_executable(DiscreteMarchingCubes MACOSX_BUNDLE DiscreteMarchingCubes.cxx ) target_link_libraries(DiscreteMarchingCubes PRIVATE${VTK_LIBRARIES})
else ()
# include all components
add_executable(DiscreteMarchingCubes MACOSX_BUNDLE DiscreteMarchingCubes.cxx )
target_link_libraries(DiscreteMarchingCubes PRIVATE ${VTK_LIBRARIES}) # vtk_module_autoinit is needed vtk_module_autoinit( TARGETS DiscreteMarchingCubes MODULES${VTK_LIBRARIES}
)
endif ()


cd DiscreteMarchingCubes/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:

./DiscreteMarchingCubes


WINDOWS USERS

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