GLTFExporter

Description¶

The examples uses vtkGLTFExporter to save the current scene in a .gltf file. The saved file called GLTFExporter.gltf is saved in the directory where the example is run. That file can be imported using vtkGLTFImporter.

Warning

Currently the camera is not writeen properly so the exported scene will not match the imported scene.

Question

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

Code¶

GLTFExporter.cxx

#include <vtkActor.h>
#include <vtkArrowSource.h>
#include <vtkCamera.h>
#include <vtkGLTFExporter.h>
#include <vtkInteractorStyleTrackballCamera.h>
#include <vtkMath.h>
#include <vtkMinimalStandardRandomSequence.h>
#include <vtkNamedColors.h>
#include <vtkNew.h>
#include <vtkPolyData.h>
#include <vtkPolyDataMapper.h>
#include <vtkProperty.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>
#include <vtkSphereSource.h>
#include <vtkTransform.h>
#include <vtkTransformPolyDataFilter.h>

#include <array>

int main(int argc, char* argv[])
{
  if (argc < 2)
  {
    std::cout << "Usage: GLTFExporter file.gltf e.g. GLTFExporter.gltf"
              << std::endl;
    return EXIT_FAILURE;
  }
  vtkNew<vtkNamedColors> colors;

  // Set the background color.
  vtkColor3d backgroundColor = colors->GetColor3d("SlateGray");

  // Create an arrow.
  vtkNew<vtkArrowSource> arrowSource;

  // Generate a random start and end point
  double startPoint[3];
  double endPoint[3];
  vtkNew<vtkMinimalStandardRandomSequence> rng;
  rng->SetSeed(8775070); // For testing.
  for (auto i = 0; i < 3; ++i)
  {
    rng->Next();
    startPoint[i] = rng->GetRangeValue(-10, 10);
    rng->Next();
    endPoint[i] = rng->GetRangeValue(-10, 10);
  }

  // Compute a basis
  double normalizedX[3];
  double normalizedY[3];
  double normalizedZ[3];

  // The X axis is a vector from start to end
  vtkMath::Subtract(endPoint, startPoint, normalizedX);
  double length = vtkMath::Norm(normalizedX);
  vtkMath::Normalize(normalizedX);

  // The Z axis is an arbitrary vector cross X
  double arbitrary[3];
  for (auto i = 0; i < 3; ++i)
  {
    rng->Next();
    arbitrary[i] = rng->GetRangeValue(-10, 10);
  }
  vtkMath::Cross(normalizedX, arbitrary, normalizedZ);
  vtkMath::Normalize(normalizedZ);

  // The Y axis is Z cross X
  vtkMath::Cross(normalizedZ, normalizedX, normalizedY);
  vtkNew<vtkMatrix4x4> matrix;

  // Create the direction cosine matrix
  matrix->Identity();
  for (auto i = 0; i < 3; i++)
  {
    matrix->SetElement(i, 0, normalizedX[i]);
    matrix->SetElement(i, 1, normalizedY[i]);
    matrix->SetElement(i, 2, normalizedZ[i]);
  }

  // Apply the transforms
  vtkNew<vtkTransform> transform;
  transform->Translate(startPoint);
  transform->Concatenate(matrix);
  transform->Scale(length, length, length);

  // Transform the polydata
  vtkNew<vtkTransformPolyDataFilter> transformPD;
  transformPD->SetTransform(transform);
  transformPD->SetInputConnection(arrowSource->GetOutputPort());

  // Create a mapper and actor for the arrow
  vtkNew<vtkPolyDataMapper> mapper;
  vtkNew<vtkActor> actor;
#ifdef USER_MATRIX
  mapper->SetInputConnection(arrowSource->GetOutputPort());
  actor->SetUserMatrix(transform->GetMatrix());
#else
  mapper->SetInputConnection(transformPD->GetOutputPort());
#endif
  actor->SetMapper(mapper);
  actor->GetProperty()->SetColor(colors->GetColor3d("Cyan").GetData());

  // Create spheres for start and end point
  vtkNew<vtkSphereSource> sphereStartSource;
  sphereStartSource->SetCenter(startPoint);
  sphereStartSource->SetRadius(0.8);
  vtkNew<vtkPolyDataMapper> sphereStartMapper;
  sphereStartMapper->SetInputConnection(sphereStartSource->GetOutputPort());
  vtkNew<vtkActor> sphereStart;
  sphereStart->SetMapper(sphereStartMapper);
  sphereStart->GetProperty()->SetColor(colors->GetColor3d("Yellow").GetData());

  vtkNew<vtkSphereSource> sphereEndSource;
  sphereEndSource->SetCenter(endPoint);
  sphereEndSource->SetRadius(0.8);
  vtkNew<vtkPolyDataMapper> sphereEndMapper;
  sphereEndMapper->SetInputConnection(sphereEndSource->GetOutputPort());
  vtkNew<vtkActor> sphereEnd;
  sphereEnd->SetMapper(sphereEndMapper);
  sphereEnd->GetProperty()->SetColor(colors->GetColor3d("Magenta").GetData());

  // Create a renderer, render window, and interactor
  vtkNew<vtkRenderer> renderer;
  vtkNew<vtkRenderWindow> renderWindow;
  renderWindow->AddRenderer(renderer);
  renderWindow->SetSize(640, 480);
  renderWindow->SetWindowName("GLTFExporter");

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

  // Add the actor to the scene
  renderer->AddActor(actor);
  renderer->AddActor(sphereStart);
  renderer->AddActor(sphereEnd);
  renderer->SetBackground(backgroundColor.GetData());

  // Render and interact
  renderWindow->Render();
  renderer->GetActiveCamera()->Azimuth(30);
  renderer->GetActiveCamera()->Elevation(30);
  renderer->GetActiveCamera()->Roll(30);
  renderer->ResetCameraClippingRange();

  renderWindowInteractor->Start();

  vtkNew<vtkGLTFExporter> writer;
  writer->SetFileName(argv[1]);
  writer->InlineDataOn();
  writer->SetRenderWindow(renderWindow);
  writer->Write();

  return EXIT_SUCCESS;
}

CMakeLists.txt¶

cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

project(GLTFExporter)

find_package(VTK COMPONENTS 
  vtkCommonColor
  vtkCommonCore
  vtkCommonDataModel
  vtkCommonTransforms
  vtkFiltersGeneral
  vtkFiltersSources
  vtkIOExport
  vtkIOExportOpenGL2
  vtkIOExportPDF
  vtkInteractionStyle
  vtkRenderingContextOpenGL2
  vtkRenderingCore
  vtkRenderingFreeType
  vtkRenderingGL2PSOpenGL2
  vtkRenderingOpenGL2
  QUIET
)

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

Download and Build GLTFExporter¶

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

cd GLTFExporter/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:

./GLTFExporter

WINDOWS USERS

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