Visualization Toolkit - How to read and render multiple objects?

Question

I'm trying to read and render multiple files in a directory (when combined they form an object) using vtk. But so far I'm getting the following error:

ERROR: In D:\VTK\VTK-src\IO\XML\vtkXMLReader.cxx, line 283
vtkXMLPolyDataReader (00D1B560): Error opening file D:\3d models\Dist\.

ERROR: In D:\VTK\VTK-src\Common\ExecutionModel\vtkExecutive.cxx, line 782
vtkCompositeDataPipeline (00CC2078): Algorithm
vtkXMLPolyDataReader(00D1B560) returned failure for request: vtkInformation
(00D20688)
  Debug: Off
  Modified Time: 8721
  Reference Count: 1
  Registered Events: (none)
  Request: REQUEST_DATA
  FORWARD_DIRECTION: 0
  ALGORITHM_AFTER_FORWARD: 1
  FROM_OUTPUT_PORT: 0 

So far what I've tried is reading only 1 file instead of multiple files, but I still the error I mentioned above.

Here's the coding I'm working on:

int main(int argc, char *argv[])
{
  std::string directoryName = "D:\\3d models\\Dist\\" ;

  vtkSmartPointer<vtkDirectory> directory = vtkSmartPointer<vtkDirectory>::New();
  int opened = directory->Open(directoryName.c_str());

  if(!opened)
  {
    std::cout << "No es posible abrir este directorio!" << std::endl;
    return EXIT_FAILURE;
  }

  int numberOfFiles = directory->GetNumberOfFiles();
  std::cout << "NUmero de archivos: " << numberOfFiles << std::endl;

  for (int i = 0; i < numberOfFiles; i++)
  {
    std::string fileString = directoryName;
    ////fileString += "/";
    fileString += directory->GetFile(i);

    std::string ext = vtksys::SystemTools::GetFilenameLastExtension(fileString);
    std::cout << fileString.c_str() << " extension: " << ext << std::endl;

    std::string name = vtksys::SystemTools::GetFilenameWithoutLastExtension(fileString);    
    std::cout << "nombre: " << name << std::endl;

    const char*cstr = fileString.c_str();
    std::cout << cstr << endl;

        vtkSmartPointer<vtkXMLPolyDataReader> reader =
            vtkSmartPointer<vtkXMLPolyDataReader>::New();
        reader->SetFileName(cstr);
        reader->Update();
        reader->GetOutput();

        vtkSmartPointer<vtkTransform> transform =
            vtkSmartPointer<vtkTransform>::New();
        transform->Scale(.005, .005, .005);

        vtkSmartPointer<vtkTransformFilter> transformFilter =
            vtkSmartPointer<vtkTransformFilter>::New();
        transformFilter->SetInputConnection(reader->GetOutputPort());
        transformFilter->SetTransform(transform);

        // Visualizar
        vtkSmartPointer<vtkPolyDataMapper> mapper =
            vtkSmartPointer<vtkPolyDataMapper>::New();
        mapper->SetInputConnection(transformFilter->GetOutputPort());

        vtkSmartPointer<vtkActor> actor =
            vtkSmartPointer<vtkActor>::New();
        actor->SetPosition(1.1, .5, .1);
        actor->SetMapper(mapper);

        vtkSmartPointer<vtkOpenVRRenderer> renderer =
            vtkSmartPointer<vtkOpenVRRenderer>::New();
        vtkSmartPointer<vtkOpenVRRenderWindow> renderWindow =
            vtkSmartPointer<vtkOpenVRRenderWindow>::New();
        renderWindow->AddRenderer(renderer);
        vtkSmartPointer<vtkOpenVRRenderWindowInteractor> renderWindowInteractor =
            vtkSmartPointer<vtkOpenVRRenderWindowInteractor>::New();
        renderWindowInteractor->SetRenderWindow(renderWindow);

        vtkNew<vtkOpenVRCamera> cam;
        renderer->SetActiveCamera(cam);

        renderer->AddActor(actor);
        renderer->SetBackground(.2, .3, .4);

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

  }

  return EXIT_SUCCESS;
}

What am I missing? I've tried with different type of files but I still haven't been able to read and render anything using this method.

Answer 1

It looks like the first entry when you list the files in a folder is "." (which is normal), so the path to the file you try to open is "D:\3d models\Dist\." and it is not a valid file for vtkXMLPolyDataReader.

You should only try to open vtk files written with vtkXMLPolyDataWriter. For example by checking the extension is ".vtp" (or whatever extension you used to save the files containing your vtkPolyData models).

Check the extension in the first part of your loop:

for (int i = 0; i < numberOfFiles; i++)
  {
    std::string fileString = directoryName;
    ////fileString += "/";
    fileString += directory->GetFile(i);

    std::string ext = vtksys::SystemTools::GetFilenameLastExtension(fileString);
    std::cout << fileString.c_str() << " extension: " << ext << std::endl;

    // add this line here to skip "." and "..", also fix the extension if not .xml
    if (ext.find(".vtp") == std::string::npos) continue;

    (...)

I also suspect you are trying to use vtkXMLPolyDataReader while you should use vtkPolyDataReader (this really depends on what writer was used to produce the files). vtkXMLPolyDataReader is the standard reader for .vtp files.

Last, you are creating a renderer, a rendering window and a camera inside the loop: it means one window per object. It's uncommon, is that what you want?

Long story short: you need at least one renderer and one window to display one or many models. Your models are represented by an actor each: the window is where the renderer draws (one or many) actors. A renderer is a rendering pass: of course you can have one rendering pass for each actor, but unless you are sure you need it, you don't.

Here's your code, modified as I would do at your place:

int main(int argc, char *argv[])
{
    std::string directoryName = "D:\\3d models\\Dist\\" ;

    vtkSmartPointer<vtkOpenVRRenderer> renderer =
        vtkSmartPointer<vtkOpenVRRenderer>::New();
    vtkSmartPointer<vtkOpenVRRenderWindow> renderWindow =
            vtkSmartPointer<vtkOpenVRRenderWindow>::New();
    renderWindow->AddRenderer(renderer);
    vtkSmartPointer<vtkOpenVRRenderWindowInteractor> renderWindowInteractor =
            vtkSmartPointer<vtkOpenVRRenderWindowInteractor>::New();
    renderWindowInteractor->SetRenderWindow(renderWindow);
    vtkNew<vtkOpenVRCamera> cam;
    renderer->SetActiveCamera(cam);
    renderer->SetBackground(.2, .3, .4);

    vtkSmartPointer<vtkDirectory> directory = vtkSmartPointer<vtkDirectory>::New();
    int opened = directory->Open(directoryName.c_str());

    if(!opened)
    {
        std::cout << "No es posible abrir este directorio!" << std::endl;
        return EXIT_FAILURE;
    }

    int numberOfFiles = directory->GetNumberOfFiles();
    std::cout << "NUmero de archivos: " << numberOfFiles << std::endl;

    for (int i = 0; i < numberOfFiles; i++)
    {
        std::string fileString = directoryName;
        ////fileString += "/";
        fileString += directory->GetFile(i);

        std::string ext = vtksys::SystemTools::GetFilenameLastExtension(fileString);
        std::cout << fileString.c_str() << " extension: " << ext << std::endl;

        if (ext.find(".vtp") == std::string::npos) continue;

        std::string name = vtksys::SystemTools::GetFilenameWithoutLastExtension(fileString);    
        std::cout << "nombre: " << name << std::endl;

        const char*cstr = fileString.c_str();
        std::cout << cstr << endl;

        vtkSmartPointer<vtkXMLPolyDataReader> reader =
                vtkSmartPointer<vtkXMLPolyDataReader>::New();
        reader->SetFileName(cstr);
        reader->Update();
        reader->GetOutput();

        vtkSmartPointer<vtkTransform> transform =
                vtkSmartPointer<vtkTransform>::New();
        transform->Scale(.005, .005, .005);

        vtkSmartPointer<vtkTransformFilter> transformFilter =
                vtkSmartPointer<vtkTransformFilter>::New();
        transformFilter->SetInputConnection(reader->GetOutputPort());
        transformFilter->SetTransform(transform);

        // Visualizar
        vtkSmartPointer<vtkPolyDataMapper> mapper =
                vtkSmartPointer<vtkPolyDataMapper>::New();
        mapper->SetInputConnection(transformFilter->GetOutputPort());

        vtkSmartPointer<vtkActor> actor =
                vtkSmartPointer<vtkActor>::New();
        actor->SetPosition(1.1, .5, .1);
        actor->SetMapper(mapper);

        renderer->AddActor(actor);
    }

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

    return EXIT_SUCCESS;
}