OffScreenRendering

Description¶

This example renders a scene directly to a file without displaying a window. You must turn on VTK_OPENGL_HAS_OSMESA in the VTK advanced build configuration.

Question

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

Code¶

OffScreenRendering.cxx

#include <vtkActor.h>
#include <vtkGraphicsFactory.h>
#include <vtkNamedColors.h>
#include <vtkNew.h>
#include <vtkPNGWriter.h>
#include <vtkPolyDataMapper.h>
#include <vtkProperty.h>
#include <vtkRenderWindow.h>
#include <vtkRenderer.h>
#include <vtkSphereSource.h>
#include <vtkWindowToImageFilter.h>

int main(int, char*[])
{
  vtkNew<vtkNamedColors> colors;

  // Setup offscreen rendering
  vtkNew<vtkGraphicsFactory> graphics_factory;
  graphics_factory->SetOffScreenOnlyMode(1);
  graphics_factory->SetUseMesaClasses(1);

  // Create a sphere
  vtkNew<vtkSphereSource> sphereSource;

  // Create a mapper and actor
  vtkNew<vtkPolyDataMapper> mapper;
  mapper->SetInputConnection(sphereSource->GetOutputPort());

  vtkNew<vtkActor> actor;
  actor->SetMapper(mapper);
  actor->GetProperty()->SetColor(colors->GetColor3d("White").GetData());

  // A renderer and render window
  vtkNew<vtkRenderer> renderer;
  vtkNew<vtkRenderWindow> renderWindow;
  renderWindow->SetOffScreenRendering(1);
  renderWindow->AddRenderer(renderer);

  // Add the actors to the scene
  renderer->AddActor(actor);
  renderer->SetBackground(colors->GetColor3d("SlateGray").GetData());

  renderWindow->Render();

  vtkNew<vtkWindowToImageFilter> windowToImageFilter;
  windowToImageFilter->SetInput(renderWindow);
  windowToImageFilter->Update();

  vtkNew<vtkPNGWriter> writer;
  writer->SetFileName("screenshot.png");
  writer->SetInputConnection(windowToImageFilter->GetOutputPort());
  writer->Write();

  return EXIT_SUCCESS;
}

CMakeLists.txt¶

cmake_minimum_required(VERSION 3.12 FATAL_ERROR)

project(OffScreenRendering)

find_package(VTK COMPONENTS 
  CommonColor
  CommonCore
  FiltersSources
  IOImage
  InteractionStyle
  RenderingContextOpenGL2
  RenderingCore
  RenderingFreeType
  RenderingGL2PSOpenGL2
  RenderingOpenGL2
)

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

Download and Build OffScreenRendering¶

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

cd OffScreenRendering/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:

./OffScreenRendering

WINDOWS USERS

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