# MedicalDemo4

VTKExamples/Cxx/Medical/MedicalDemo4

### Description¶

Volume rendering of the dataset.

Usage

Info

Note

This original source code for this example is here.

Other Languages

See (Python), (Java)

Question

### Code¶

MedicalDemo4.cxx

// Derived from VTK/Examples/Cxx/Medical4.cxx
// This example reads a volume dataset and displays it via volume rendering.
//

#include <vtkCamera.h>
#include <vtkColorTransferFunction.h>
#include <vtkFixedPointVolumeRayCastMapper.h>
#include <vtkNamedColors.h>
#include <vtkPiecewiseFunction.h>
#include <vtkRenderer.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkSmartPointer.h>
#include <vtkVolume.h>
#include <vtkVolumeProperty.h>

#include <array>

int main (int argc, char *argv[])
{
if (argc < 2)
{
cout << "Usage: " << argv[0] << "file.mhd" << endl;
return EXIT_FAILURE;
}

vtkSmartPointer<vtkNamedColors> colors =
vtkSmartPointer<vtkNamedColors>::New();

std::array<unsigned char , 4> bkg{{51, 77, 102, 255}};
colors->SetColor("BkgColor", bkg.data());

// Create the renderer, the render window, and the interactor. The renderer
// draws into the render window, the interactor enables mouse- and
// keyboard-based interaction with the scene.
vtkSmartPointer<vtkRenderer> ren =
vtkSmartPointer<vtkRenderer>::New();
vtkSmartPointer<vtkRenderWindow> renWin =
vtkSmartPointer<vtkRenderWindow>::New();
vtkSmartPointer<vtkRenderWindowInteractor> iren =
vtkSmartPointer<vtkRenderWindowInteractor>::New();
iren->SetRenderWindow(renWin);

// The following reader is used to read a series of 2D slices (images)
// that compose the volume. The slice dimensions are set, and the
// pixel spacing. The data Endianness must also be specified. The reader
// uses the FilePrefix in combination with the slice number to construct
// filenames using the format FilePrefix.%d. (In this case the FilePrefix
// is the root name of the file: quarter.)

// The volume will be displayed by ray-cast alpha compositing.
// A ray-cast mapper is needed to do the ray-casting.
vtkSmartPointer<vtkFixedPointVolumeRayCastMapper> volumeMapper =
vtkSmartPointer<vtkFixedPointVolumeRayCastMapper>::New();

// The color transfer function maps voxel intensities to colors.
// It is modality-specific, and often anatomy-specific as well.
// The goal is to one color for flesh (between 500 and 1000)
// and another color for bone (1150 and over).
vtkSmartPointer<vtkColorTransferFunction>volumeColor =
vtkSmartPointer<vtkColorTransferFunction>::New();

// The opacity transfer function is used to control the opacity
// of different tissue types.
vtkSmartPointer<vtkPiecewiseFunction> volumeScalarOpacity =
vtkSmartPointer<vtkPiecewiseFunction>::New();

// The gradient opacity function is used to decrease the opacity
// in the "flat" regions of the volume while maintaining the opacity
// at the boundaries between tissue types.  The gradient is measured
// as the amount by which the intensity changes over unit distance.
// For most medical data, the unit distance is 1mm.
vtkSmartPointer<vtkPiecewiseFunction>::New();

// The VolumeProperty attaches the color and opacity functions to the
// volume, and sets other volume properties.  The interpolation should
// be set to linear to do a high-quality rendering.  The ShadeOn option
// turns on directional lighting, which will usually enhance the
// appearance of the volume and make it look more "3D".  However,
// the quality of the shading depends on how accurately the gradient
// of the volume can be calculated, and for noisy data the gradient
// estimation will be very poor.  The impact of the shading can be
// decreased by increasing the Ambient coefficient while decreasing
// the Diffuse and Specular coefficient.  To increase the impact
// of shading, decrease the Ambient and increase the Diffuse and Specular.
vtkSmartPointer<vtkVolumeProperty> volumeProperty =
vtkSmartPointer<vtkVolumeProperty>::New();
volumeProperty->SetColor(volumeColor);
volumeProperty->SetScalarOpacity(volumeScalarOpacity);
volumeProperty->SetInterpolationTypeToLinear();
volumeProperty->SetAmbient(0.4);
volumeProperty->SetDiffuse(0.6);
volumeProperty->SetSpecular(0.2);

// The vtkVolume is a vtkProp3D (like a vtkActor) and controls the position
// and orientation of the volume in world coordinates.
vtkSmartPointer<vtkVolume> volume =
vtkSmartPointer<vtkVolume>::New();
volume->SetMapper(volumeMapper);
volume->SetProperty(volumeProperty);

// Finally, add the volume to the renderer

// Set up an initial view of the volume.  The focal point will be the
// center of the volume, and the camera position will be 400mm to the
// patient's left (which is our right).
vtkCamera *camera = ren->GetActiveCamera();
double *c = volume->GetCenter();
camera->SetViewUp (0, 0, -1);
camera->SetPosition (c[0], c[1] - 400, c[2]);
camera->SetFocalPoint (c[0], c[1], c[2]);
camera->Azimuth(30.0);
camera->Elevation(30.0);

// Set a background color for the renderer
ren->SetBackground(colors->GetColor3d("BkgColor").GetData());

// Increase the size of the render window
renWin->SetSize(640, 480);

// Interact with the data.
renWin->Render();
iren->Start();

return EXIT_SUCCESS;
}


### CMakeLists.txt¶

cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

project(MedicalDemo4)

find_package(VTK COMPONENTS
vtkCommonColor
vtkCommonCore
vtkCommonDataModel
vtkIOImage
vtkInteractionStyle
vtkRenderingContextOpenGL2
vtkRenderingCore
vtkRenderingFreeType
vtkRenderingGL2PSOpenGL2
vtkRenderingOpenGL2
vtkRenderingVolume
vtkRenderingVolumeOpenGL2 QUIET)
if (NOT VTK_FOUND)
message("Skipping MedicalDemo4: ${VTK_NOT_FOUND_MESSAGE}") return () endif() message (STATUS "VTK_VERSION:${VTK_VERSION}")
if (VTK_VERSION VERSION_LESS "8.90.0")
# old system
include(${VTK_USE_FILE}) add_executable(MedicalDemo4 MACOSX_BUNDLE MedicalDemo4.cxx ) target_link_libraries(MedicalDemo4 PRIVATE${VTK_LIBRARIES})
else ()
# include all components
target_link_libraries(MedicalDemo4 PRIVATE ${VTK_LIBRARIES}) # vtk_module_autoinit is needed vtk_module_autoinit( TARGETS MedicalDemo4 MODULES${VTK_LIBRARIES}
)
endif ()


cd MedicalDemo4/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:

./MedicalDemo4


WINDOWS USERS

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