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IsosurfaceSampling

vtk-examples/Cxx/Visualization/IsosurfaceSampling

Description

This example illustrates how to create an isosurface and create point data on that isosurface that is sampled from another dataset. This example creates an isosurface of a sphere and then uses the vtkProbeFilter to compute point data from a sampled cylinder.

Note

All point data is sampled, even the normals. This example restores the original isosurface normals after the probe. The example has one optional command line argument that controls the sample resolution of the sphere and cylinder. The default is 50.

Other languages

See (Python)

Question

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

Code

IsosurfaceSampling.cxx

#include <vtkActor.h>
#include <vtkCylinder.h>
#include <vtkNamedColors.h>
#include <vtkNew.h>
#include <vtkPointData.h>
#include <vtkPolyDataMapper.h>
#include <vtkProbeFilter.h>
#include <vtkProperty.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>
#include <vtkSampleFunction.h>
#include <vtkSphere.h>
#include <vtkVersion.h>

// vtkFlyingEdges3D was introduced in VTK >= 8.2
#if VTK_MAJOR_VERSION >= 9 || (VTK_MAJOR_VERSION >= 8 && VTK_MINOR_VERSION >= 2)
#define USE_FLYING_EDGES
#else
#undef USE_FLYING_EDGES
#endif

#ifdef USE_FLYING_EDGES
#include <vtkFlyingEdges3D.h>
#else
#include <vtkMarchingCubes.h>
#endif

int main(int argc, char* argv[])
{
  int resolution = 50;
  if (argc > 1)
  {
    resolution = atoi(argv[1]);
  }

  vtkNew<vtkNamedColors> colors;

  // Create a sampled sphere.
  vtkNew<vtkSphere> implicitSphere;
  double radius = 1.0;
  implicitSphere->SetRadius(radius);

  vtkNew<vtkSampleFunction> sampledSphere;
  sampledSphere->SetSampleDimensions(resolution, resolution, resolution);
  double xMin = -radius * 2.0;
  double xMax = radius * 2.0;
  sampledSphere->SetModelBounds(xMin, xMax, xMin, xMax, xMin, xMax);
  sampledSphere->SetImplicitFunction(implicitSphere);

#ifdef USE_FLYING_EDGES
  vtkNew<vtkFlyingEdges3D> isoSphere;
#else
  vtkNew<vtkMarchingCubes> isoSphere;
#endif
  isoSphere->SetValue(0, 1.0);
  isoSphere->SetInputConnection(sampledSphere->GetOutputPort());

  // Create a sampled cylinder.
  vtkNew<vtkCylinder> implicitCylinder;
  implicitCylinder->SetRadius(radius / 2.0);
  vtkNew<vtkSampleFunction> sampledCylinder;
  sampledCylinder->SetSampleDimensions(resolution, resolution, resolution);
  sampledCylinder->SetModelBounds(xMin, xMax, xMin, xMax, xMin, xMax);
  sampledCylinder->SetImplicitFunction(implicitCylinder);

  // Probe cylinder with the sphere isosurface.
  vtkNew<vtkProbeFilter> probeCylinder;
  probeCylinder->SetInputConnection(0, isoSphere->GetOutputPort());
  probeCylinder->SetInputConnection(1, sampledCylinder->GetOutputPort());
  probeCylinder->Update();

  // Restore the original normals.
  probeCylinder->GetOutput()->GetPointData()->SetNormals(
      isoSphere->GetOutput()->GetPointData()->GetNormals());

  std::cout << "Scalar range: "
            << probeCylinder->GetOutput()->GetScalarRange()[0] << ", "
            << probeCylinder->GetOutput()->GetScalarRange()[1] << std::endl;

  // Create a mapper and actor.
  vtkNew<vtkPolyDataMapper> mapSphere;
  mapSphere->SetInputConnection(probeCylinder->GetOutputPort());
  mapSphere->SetScalarRange(probeCylinder->GetOutput()->GetScalarRange());

  vtkNew<vtkActor> sphere;
  sphere->SetMapper(mapSphere);

  // Visualize
  vtkNew<vtkRenderer> renderer;
  vtkNew<vtkRenderWindow> renderWindow;
  renderWindow->AddRenderer(renderer);
  renderWindow->SetWindowName("IsosurfaceSampling");

  vtkNew<vtkRenderWindowInteractor> renderWindowInteractor;
  renderWindowInteractor->SetRenderWindow(renderWindow);

  renderer->AddActor(sphere);
  renderer->SetBackground(colors->GetColor3d("AliceBlue").GetData());

  renderWindow->Render();
  renderWindowInteractor->Start();

  return EXIT_SUCCESS;
}

CMakeLists.txt

cmake_minimum_required(VERSION 3.12 FATAL_ERROR)

project(IsosurfaceSampling)

find_package(VTK COMPONENTS 
  CommonColor
  CommonCore
  CommonDataModel
  FiltersCore
  ImagingHybrid
  InteractionStyle
  RenderingContextOpenGL2
  RenderingCore
  RenderingFreeType
  RenderingGL2PSOpenGL2
  RenderingOpenGL2
)

if (NOT VTK_FOUND)
  message(FATAL_ERROR "IsosurfaceSampling: 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(IsosurfaceSampling MACOSX_BUNDLE IsosurfaceSampling.cxx )
  target_link_libraries(IsosurfaceSampling PRIVATE ${VTK_LIBRARIES}
)
# vtk_module_autoinit is needed
vtk_module_autoinit(
  TARGETS IsosurfaceSampling
  MODULES ${VTK_LIBRARIES}
)

Download and Build IsosurfaceSampling

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

cd IsosurfaceSampling/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:

./IsosurfaceSampling

WINDOWS USERS

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