Skip to content

PseudoVolumeRendering

vtk-examples/Cxx/VolumeRendering/PseudoVolumeRendering


Description

This example uses 100 cut planes with opacity of 0.05. Rendered back-to-front to simulate volume rendering.

Other languages

See (Python)

Question

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

Code

PseudoVolumeRendering.cxx

#include <vtkActor.h>
#include <vtkCamera.h>
#include <vtkContourFilter.h>
#include <vtkCutter.h>
#include <vtkExtractGrid.h>
#include <vtkLookupTable.h>
#include <vtkMultiBlockDataSet.h>
#include <vtkMultiBlockPLOT3DReader.h>
#include <vtkNamedColors.h>
#include <vtkNew.h>
#include <vtkPlane.h>
#include <vtkPolyDataMapper.h>
#include <vtkPolyDataNormals.h>
#include <vtkProperty.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>
#include <vtkStripper.h>
#include <vtkStructuredGrid.h>
#include <vtkStructuredGridOutlineFilter.h>
#include <vtkTubeFilter.h>

// Perform psuedo volume rendering in a structured grid by compositing
// translucent cut planes. This same trick can be used for unstructured
// grids. Note that for better results, more planes can be created. Also,
// if your data is vtkImageData, there are much faster methods for volume
// rendering.

int main(int argc, char* argv[])
{
  if (argc < 3)
  {
    std::cout << "Usage: " << argv[0] << " combxyz.bin combq.bin" << std::endl;
    return EXIT_FAILURE;
  }

  vtkNew<vtkNamedColors> colors;

  // Create pipeline. Read structured grid data.
  //
  vtkNew<vtkMultiBlockPLOT3DReader> pl3d;
  pl3d->SetXYZFileName(argv[1]);
  pl3d->SetQFileName(argv[2]);
  pl3d->SetScalarFunctionNumber(100);
  pl3d->SetVectorFunctionNumber(202);
  pl3d->Update();

  vtkStructuredGrid* pl3dOutput =
      dynamic_cast<vtkStructuredGrid*>(pl3d->GetOutput()->GetBlock(0));

  // A convenience, use this filter to limit data for experimentation.
  vtkNew<vtkExtractGrid> extract;
  extract->SetVOI(1, 55, -1000, 1000, -1000, 1000);
  extract->SetInputData(pl3dOutput);

  // The (implicit) plane is used to do the cutting
  vtkNew<vtkPlane> plane;
  plane->SetOrigin(0, 4, 2);
  plane->SetNormal(0, 1, 0);

  // The cutter is set up to process each contour value over all cells
  // (SetSortByToSortByCell). This results in an ordered output of polygons
  // which is key to the compositing.
  vtkNew<vtkCutter> cutter;
  cutter->SetInputConnection(extract->GetOutputPort());
  cutter->SetCutFunction(plane);
  cutter->GenerateCutScalarsOff();
  cutter->SetSortByToSortByCell();

  vtkNew<vtkLookupTable> clut;
  clut->SetHueRange(0, .67);
  clut->Build();

  vtkNew<vtkPolyDataMapper> cutterMapper;
  cutterMapper->SetInputConnection(cutter->GetOutputPort());
  cutterMapper->SetScalarRange(.18, .7);
  cutterMapper->SetLookupTable(clut);

  vtkNew<vtkActor> cut;
  cut->SetMapper(cutterMapper);

  // Add in some surface geometry for interest.
  vtkNew<vtkContourFilter> iso;
  iso->SetInputData(pl3dOutput);
  iso->SetValue(0, .22);

  vtkNew<vtkPolyDataNormals> normals;
  normals->SetInputConnection(iso->GetOutputPort());
  normals->SetFeatureAngle(60);

  vtkNew<vtkPolyDataMapper> isoMapper;
  isoMapper->SetInputConnection(normals->GetOutputPort());
  isoMapper->ScalarVisibilityOff();

  vtkNew<vtkActor> isoActor;
  isoActor->SetMapper(isoMapper);
  isoActor->GetProperty()->SetDiffuseColor(
      colors->GetColor3d("Tomato").GetData());
  isoActor->GetProperty()->SetSpecularColor(
      colors->GetColor3d("White").GetData());
  isoActor->GetProperty()->SetDiffuse(.8);
  isoActor->GetProperty()->SetSpecular(.5);
  isoActor->GetProperty()->SetSpecularPower(30);

  vtkNew<vtkStructuredGridOutlineFilter> outline;
  outline->SetInputData(pl3dOutput);

  vtkNew<vtkStripper> outlineStrip;
  outlineStrip->SetInputConnection(outline->GetOutputPort());

  vtkNew<vtkTubeFilter> outlineTubes;
  outlineTubes->SetInputConnection(outline->GetOutputPort());
  outlineTubes->SetInputConnection(outlineStrip->GetOutputPort());
  outlineTubes->SetRadius(.1);

  vtkNew<vtkPolyDataMapper> outlineMapper;
  outlineMapper->SetInputConnection(outlineTubes->GetOutputPort());

  vtkNew<vtkActor> outlineActor;
  outlineActor->SetMapper(outlineMapper);

  // Create the RenderWindow, Renderer and Interactor
  //
  vtkNew<vtkRenderer> ren1;
  vtkNew<vtkRenderWindow> renWin;
  renWin->AddRenderer(ren1);
  vtkNew<vtkRenderWindowInteractor> iren;

  iren->SetRenderWindow(renWin);

  // Add the actors to the renderer, set the background and size
  //
  ren1->AddActor(outlineActor);
  outlineActor->GetProperty()->SetColor(colors->GetColor3d("Banana").GetData());
  ren1->AddActor(isoActor);
  isoActor->VisibilityOn();
  ren1->AddActor(cut);

  unsigned int n = 20;
  double opacity = 1.0 / (static_cast<double>(n)) * 5.0;
  cut->GetProperty()->SetOpacity(1);
  ren1->SetBackground(colors->GetColor3d("Slategray").GetData());

  renWin->SetSize(640, 480);
  renWin->SetWindowName("PseudoVolumeRendering");

  ren1->GetActiveCamera()->SetClippingRange(3.95297, 50);
  ren1->GetActiveCamera()->SetFocalPoint(9.71821, 0.458166, 29.3999);
  ren1->GetActiveCamera()->SetPosition(2.7439, -37.3196, 38.7167);
  ren1->GetActiveCamera()->ComputeViewPlaneNormal();
  ren1->GetActiveCamera()->SetViewUp(-0.16123, 0.264271, 0.950876);

  // Cut: generates n cut planes normal to camera's view plane
  //
  plane->SetNormal(ren1->GetActiveCamera()->GetViewPlaneNormal());
  plane->SetOrigin(ren1->GetActiveCamera()->GetFocalPoint());
  cutter->GenerateValues(n, -5, 5);
  clut->SetAlphaRange(opacity, opacity);
  renWin->Render();

  iren->Start();

  return EXIT_SUCCESS;
}

CMakeLists.txt

cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

project(PseudoVolumeRendering)

find_package(VTK COMPONENTS 
  vtkCommonColor
  vtkCommonCore
  vtkCommonDataModel
  vtkFiltersCore
  vtkFiltersExtraction
  vtkIOParallel
  vtkInteractionStyle
  vtkRenderingContextOpenGL2
  vtkRenderingCore
  vtkRenderingFreeType
  vtkRenderingGL2PSOpenGL2
  vtkRenderingOpenGL2
  QUIET
)

if (NOT VTK_FOUND)
  message("Skipping PseudoVolumeRendering: ${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(PseudoVolumeRendering MACOSX_BUNDLE PseudoVolumeRendering.cxx )
  target_link_libraries(PseudoVolumeRendering PRIVATE ${VTK_LIBRARIES})
else ()
  # include all components
  add_executable(PseudoVolumeRendering MACOSX_BUNDLE PseudoVolumeRendering.cxx )
  target_link_libraries(PseudoVolumeRendering PRIVATE ${VTK_LIBRARIES})
  # vtk_module_autoinit is needed
  vtk_module_autoinit(
    TARGETS PseudoVolumeRendering
    MODULES ${VTK_LIBRARIES}
    )
endif ()

Download and Build PseudoVolumeRendering

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

cd PseudoVolumeRendering/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:

./PseudoVolumeRendering

WINDOWS USERS

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