diff --git a/CMakeLists.txt b/CMakeLists.txt
index f34243f..9ae03ef 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -2,7 +2,37 @@ cmake_minimum_required(VERSION 3.15)
 
 project(pfe)
 
-add_subdirectory(external/vtk)
+set(VTK_COMPONENTS
+  VTK::CommonCore
+  VTK::IOCore
+  VTK::FiltersCore
+  VTK::CommonColor
+  VTK::CommonDataModel
+  VTK::IOLegacy
+  VTK::IOXML)
+set(ENABLE_VIEWER OFF CACHE BOOL "Enable the 3D viewer, depends on Qt.")
+if(ENABLE_VIEWER)
+  list(APPEND VTK_COMPONENTS
+	VTK::RenderingCore
+	VTK::ViewsCore
+	VTK::GUISupportQt
+	VTK::RenderingQt
+	VTK::ViewsQt
+	VTK::RenderingVolume
+	VTK::RenderingVolumeOpenGL2)
+endif()
+
+set(USE_SYSTEM_VTK NO CACHE BOOL
+  "Use the version of vtk installed in the system instead of downloading and compiling it ourselves.")
+if(USE_SYSTEM_VTK)
+  list(TRANSFORM VTK_COMPONENTS REPLACE "VTK::" ""
+	OUTPUT_VARIABLE VTK_PACKAGE_COMPONENTS)
+  message("VTK_COMPONENTS: ${VTK_COMPONENTS}")
+  message("VTK_PACKAGE_COMPONENTS: ${VTK_PACKAGE_COMPONENTS}")
+  find_package(VTK COMPONENTS ${VTK_PACKAGE_COMPONENTS})
+else()
+  add_subdirectory(external/vtk)
+endif()
 
 add_executable(pfe)
 
@@ -19,18 +49,8 @@ target_sources(pfe PRIVATE
   src/external_points_filter.cc
   src/external_points_filter.h)
 
-target_link_libraries(pfe PRIVATE
-  VTK::CommonCore
-  VTK::ViewsCore
-  VTK::RenderingCore
-  VTK::IOCore
-  VTK::FiltersCore
-  VTK::CommonColor
-  VTK::GUISupportQt
-  VTK::RenderingQt
-  VTK::ViewsQt
-  VTK::RenderingVolume
-  VTK::CommonDataModel
-  VTK::IOLegacy
-  VTK::IOXML
-  VTK::RenderingVolumeOpenGL2)
+target_link_libraries(pfe PRIVATE ${VTK_COMPONENTS})
+
+if(ENABLE_VIEWER)
+  target_compile_definitions(pfe PRIVATE ENABLE_VIEWER)
+endif()
diff --git a/src/main.cc b/src/main.cc
index 857e8d0..b2f7f35 100644
--- a/src/main.cc
+++ b/src/main.cc
@@ -5,8 +5,12 @@
 
 #include <vtkCellData.h>
 #include <vtkUnstructuredGrid.h>
-#include <vtkCamera.h>
+#include <vtkUnstructuredGridReader.h>
+#include <vtkUnstructuredGridWriter.h>
+
+#ifdef USE_VIEWER
 #include <vtkNamedColors.h>
+#include <vtkCamera.h>
 #include <vtkVolumeProperty.h>
 #include <vtkRenderWindow.h>
 #include <vtkRenderWindowInteractor.h>
@@ -14,9 +18,8 @@
 #include <vtkVolumeMapper.h>
 #include <vtkVolume.h>
 #include <vtkOpenGLProjectedTetrahedraMapper.h>
-#include <vtkUnstructuredGridReader.h>
-#include <vtkUnstructuredGridWriter.h>
 #include <vtkPiecewiseFunction.h>
+#endif
 
 #include <array>
 
@@ -92,34 +95,35 @@ int main(int argc, char **argv) {
 	writer->SetFileName("out.vtk");
 	writer->Write();
 
-	// /* Volume rendering properties */
-	// vtkNew<vtkOpenGLProjectedTetrahedraMapper> volumeMapper;
-	// volumeMapper->SetInputConnection(externalPointsFilter->GetOutputPort());
-	// vtkNew<vtkVolume> volume;
-	// volume->SetMapper(volumeMapper);
-	// vtkNew<vtkPiecewiseFunction> transferFunction;
-	// transferFunction->AddPoint(-1, 0);
-	// transferFunction->AddPoint(1, 1);
-	// volume->GetProperty()->SetScalarOpacity(transferFunction);
-	// volume->GetProperty()->SetColor(transferFunction);
-
-	// /* Renderer */
-	// vtkNew<vtkNamedColors> colors;
-	// std::array<unsigned char, 4> bkg{{26, 51, 102, 255}};
-	// colors->SetColor("BkgColor", bkg.data());
-	// vtkNew<vtkRenderer> renderer;
-	// renderer->AddVolume(volume);
-	// renderer->SetBackground(colors->GetColor3d("BkgColor").GetData());
-	// renderer->ResetCamera();
-	// renderer->GetActiveCamera()->Zoom(1.5);
-	// vtkNew<vtkRenderWindow> renderWindow;
-	// renderWindow->SetSize(300, 300);
-	// renderWindow->AddRenderer(renderer);
-	// renderWindow->SetWindowName("PFE");
-	// vtkNew<vtkRenderWindowInteractor> renderWindowInteractor;
-	// renderWindowInteractor->SetRenderWindow(renderWindow);
-	// renderWindow->Render();
-	// renderWindowInteractor->Start();
+#ifdef USE_VIEWER
+	/* Volume rendering properties */
+	vtkNew<vtkOpenGLProjectedTetrahedraMapper> volumeMapper;
+	volumeMapper->SetInputConnection(externalPointsFilter->GetOutputPort());
+	vtkNew<vtkVolume> volume;
+	volume->SetMapper(volumeMapper);
+	vtkNew<vtkPiecewiseFunction> transferFunction;
+	transferFunction->AddPoint(-1, 0);
+	transferFunction->AddPoint(1, 1);
+	volume->GetProperty()->SetScalarOpacity(transferFunction);
+	volume->GetProperty()->SetColor(transferFunction);
 
+	/* Renderer */
+	vtkNew<vtkNamedColors> colors;
+	std::array<unsigned char, 4> bkg{{26, 51, 102, 255}};
+	colors->SetColor("BkgColor", bkg.data());
+	vtkNew<vtkRenderer> renderer;
+	renderer->AddVolume(volume);
+	renderer->SetBackground(colors->GetColor3d("BkgColor").GetData());
+	renderer->ResetCamera();
+	renderer->GetActiveCamera()->Zoom(1.5);
+	vtkNew<vtkRenderWindow> renderWindow;
+	renderWindow->SetSize(300, 300);
+	renderWindow->AddRenderer(renderer);
+	renderWindow->SetWindowName("PFE");
+	vtkNew<vtkRenderWindowInteractor> renderWindowInteractor;
+	renderWindowInteractor->SetRenderWindow(renderWindow);
+	renderWindow->Render();
+	renderWindowInteractor->Start();
+#endif
 	return EXIT_SUCCESS;
 }