[vtkusers] MAC offscreenrendering

[Matthias Müller]

Hello,

When I implement offscreen rendering on mac there is always a white window poping up The offscreen rendering itself seems to work correctly: the generated image file contains my vtk Scene.
VTK 5.6 (compiled with Cocoa and Mesa)
Mac OSX 10.6.7

Example sourcecode:

 vtkSmartPointer<vtkRenderer> renderer = vtkRenderer::New();
  vtkSmartPointer<vtkRenderWindow> renWin = vtkRenderWindow::New();
  renWin->SetOffScreenRendering(1);
  renWin->AddRenderer(renderer);

  // sphere1: the outer sphere
  vtkSmartPointer<vtkSphereSource> sphere1 = vtkSphereSource::New();
  sphere1->SetThetaResolution(100);
  sphere1->SetPhiResolution(100);
  sphere1->SetRadius(1);
  sphere1->Update();
  vtkSmartPointer<vtkPolyDataMapper> sphereMapper = vtkPolyDataMapper::New();
  sphereMapper->SetInputConnection(sphere1->GetOutputPort());
  vtkSmartPointer<vtkActor> sphereActor = vtkActor::New();
  sphereActor->SetMapper(sphereMapper);
  renderer->AddActor(sphereActor);
  renderer->SetBackground(1,1,1);
  renWin->SetSize(300,300);
  vtkSmartPointer<vtkWindowToImageFilter> toImage = vtkWindowToImageFilter::New();
  toImage->SetInput(renWin);
  renWin->Render();
  vtkSmartPointer<vtkPNGWriter> writer = vtkPNGWriter::New();
  writer->SetInput(toImage->GetOutput());
  writer->SetFileName("***some filename**");
  writer->Write();

How can I get rid of the annoying popup window? 

Please advise

Matthias
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