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->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 3.12 FATAL_ERROR)

project(GLTFExporter)

find_package(VTK COMPONENTS 
  CommonColor
  CommonCore
  CommonDataModel
  CommonTransforms
  FiltersGeneral
  FiltersSources
  IOExport
  IOExportOpenGL2
  IOExportPDF
  InteractionStyle
  RenderingContextOpenGL2
  RenderingCore
  RenderingFreeType
  RenderingGL2PSOpenGL2
  RenderingOpenGL2
)

if (NOT VTK_FOUND)
  message(FATAL_ERROR "GLTFExporter: 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(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}
)

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.