RayCastIsosurface

Info

The example uses src/Testing/Data/FullHead.mhd which references src/Testing/Data/FullHead.raw.gz.

Description¶

This examples show how volume rendering can produce isosurface-like images. Using vtkOpenGLGPUVolumeRayCastMapper with an isosurface blend mode, two isosurfaces are created using appropriate transfer functions. The effect is similar to what is shown in MedicalDemo2. The user can specify the .mhd file and the two isosurface values. The example uses 500 and 1150 for the two isosurface values. The volume rendering "surfaces" are fuzzier than the hard surfaces created by vtkMarchingCubes in MedicalDemo3.

Usage

    RayCastIsosurface FullHead.mhd 500 1150

Info

The example uses src/Testing/Data/FullHead.mhd which references src/Testing/Data/FullHead.raw.gz.

Other languages

See (PythonicAPI)

Question

If you have a question about this example, please use the VTK Discourse Forum

Code¶

RayCastIsosurface.cxx

#include <vtkCamera.h>
#include <vtkColorTransferFunction.h>
#include <vtkContourValues.h>
#include <vtkInteractorStyleTrackballCamera.h>
#include <vtkMetaImageReader.h>
#include <vtkNamedColors.h>
#include <vtkNew.h>
#include <vtkOpenGLGPUVolumeRayCastMapper.h>
#include <vtkPiecewiseFunction.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>
#include <vtkVolume.h>
#include <vtkVolumeProperty.h>

#include <iostream>

int main(int argc, char* argv[])
{
  double iso1 = 500.0;
  double iso2 = 1150.0;

  if (argc < 2)
  {
    std::cout << "Usage: " << argv[0] << " file.mnd [iso1=500] [iso2=1150]"
              << std::endl;
    std::cout << "e.g. FullHead.mhd 500 1150" << std::endl;
    return EXIT_FAILURE;
  }

  vtkNew<vtkMetaImageReader> reader;
  reader->SetFileName(argv[1]);

  vtkNew<vtkNamedColors> colors;

  vtkNew<vtkOpenGLGPUVolumeRayCastMapper> mapper;
  mapper->SetInputConnection(reader->GetOutputPort());
  mapper->AutoAdjustSampleDistancesOff();
  mapper->SetSampleDistance(0.5);
  mapper->SetBlendModeToIsoSurface();

  if (argc > 3)
  {
    iso1 = atof(argv[2]);
    iso2 = atof(argv[3]);
  }
  vtkNew<vtkColorTransferFunction> colorTransferFunction;
  colorTransferFunction->RemoveAllPoints();
  colorTransferFunction->AddRGBPoint(iso2,
                                     colors->GetColor3d("ivory").GetData()[0],
                                     colors->GetColor3d("ivory").GetData()[1],
                                     colors->GetColor3d("ivory").GetData()[2]);
  colorTransferFunction->AddRGBPoint(iso1,
                                     colors->GetColor3d("flesh").GetData()[0],
                                     colors->GetColor3d("flesh").GetData()[1],
                                     colors->GetColor3d("flesh").GetData()[2]);

  vtkNew<vtkPiecewiseFunction> scalarOpacity;
  scalarOpacity->AddPoint(iso1, .3);
  scalarOpacity->AddPoint(iso2, 0.6);

  vtkNew<vtkVolumeProperty> volumeProperty;
  volumeProperty->ShadeOn();
  volumeProperty->SetInterpolationTypeToLinear();
  volumeProperty->SetColor(colorTransferFunction);
  volumeProperty->SetScalarOpacity(scalarOpacity);

  vtkNew<vtkVolume> volume;
  volume->SetMapper(mapper);
  volume->SetProperty(volumeProperty);

  vtkNew<vtkRenderer> renderer;
  renderer->AddVolume(volume);
  renderer->SetBackground(colors->GetColor3d("cornflower").GetData());
  renderer->ResetCamera();

  vtkNew<vtkRenderWindow> renderWindow;
  renderWindow->SetSize(800, 600);
  renderWindow->AddRenderer(renderer);
  renderWindow->SetWindowName("RayCastIsosurface");

  vtkNew<vtkInteractorStyleTrackballCamera> style;

  vtkNew<vtkRenderWindowInteractor> interactor;
  interactor->SetRenderWindow(renderWindow);
  interactor->SetInteractorStyle(style);

  // Add some contour values to draw iso surfaces
  volumeProperty->GetIsoSurfaceValues()->SetValue(0, iso1);
  volumeProperty->GetIsoSurfaceValues()->SetValue(1, iso2);

  // Generate a good view
  vtkNew<vtkCamera> aCamera;
  aCamera->SetViewUp(0, 0, -1);
  aCamera->SetPosition(0, -1, 0);
  aCamera->SetFocalPoint(0, 0, 0);

  renderer->SetActiveCamera(aCamera);
  renderer->ResetCamera();

  aCamera->Azimuth(30.0);
  aCamera->Elevation(30.0);
  aCamera->Dolly(1.5);
  renderer->ResetCameraClippingRange();

  renderWindow->Render();

  interactor->Start();

  return EXIT_SUCCESS;
}

CMakeLists.txt¶

cmake_minimum_required(VERSION 3.12 FATAL_ERROR)

project(RayCastIsosurface)

find_package(VTK COMPONENTS 
  CommonColor
  CommonCore
  CommonDataModel
  CommonMisc
  IOImage
  InteractionStyle
  RenderingContextOpenGL2
  RenderingCore
  RenderingFreeType
  RenderingGL2PSOpenGL2
  RenderingOpenGL2
  RenderingVolumeOpenGL2
)

if (NOT VTK_FOUND)
  message(FATAL_ERROR "RayCastIsosurface: Unable to find the VTK build folder.")
endif()

# Prevent a "command line is too long" failure in Windows.
set(CMAKE_NINJA_FORCE_RESPONSE_FILE "ON" CACHE BOOL "Force Ninja to use response files.")
add_executable(RayCastIsosurface MACOSX_BUNDLE RayCastIsosurface.cxx )
  target_link_libraries(RayCastIsosurface PRIVATE ${VTK_LIBRARIES}
)
# vtk_module_autoinit is needed
vtk_module_autoinit(
  TARGETS RayCastIsosurface
  MODULES ${VTK_LIBRARIES}
)

Download and Build RayCastIsosurface¶

Click here to download RayCastIsosurface and its CMakeLists.txt file. Once the tarball RayCastIsosurface.tar has been downloaded and extracted,

cd RayCastIsosurface/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:

./RayCastIsosurface

WINDOWS USERS

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