ENH: Added a regression test for vtkPolyDataSilhouette.

This test was derived from the Wiki exmaple:
http://vtk.org/Wiki/VTK/Examples/PolyData/Silhouette

Hybrid/Testing/Cxx/TestPolyDataSilhouette.cxx

+#include <vtkSmartPointer.h>
+#include <vtkProperty.h>
+#include <vtkPolyData.h>
+#include <vtkPolyDataMapper.h>
+#include <vtkActor.h>
+#include <vtkRenderer.h>
+#include <vtkRenderWindow.h>
+#include <vtkRenderWindowInteractor.h>
+#include <vtkPolyDataSilhouette.h>
+#include <vtkSphereSource.h>
+#include <vtkXMLPolyDataReader.h>
+#include <vtkCleanPolyData.h>
+
+int TestPolyDataSilhouette(int argc, char *argv[])
+{
+  vtkSmartPointer<vtkPolyData> polyData;
+  if (argc < 2)
+    {
+    vtkSmartPointer<vtkSphereSource> sphereSource =
+      vtkSmartPointer<vtkSphereSource>::New();
+    sphereSource->Update();
+
+    polyData = sphereSource->GetOutput();
+    }
+  else
+    {
+    vtkSmartPointer<vtkXMLPolyDataReader> reader =
+      vtkSmartPointer<vtkXMLPolyDataReader>::New();
+    reader->SetFileName(argv[1]);
+
+    vtkSmartPointer<vtkCleanPolyData> clean =
+      vtkSmartPointer<vtkCleanPolyData>::New();
+    clean->SetInputConnection(reader->GetOutputPort());
+    clean->Update();
+
+    polyData = clean->GetOutput();
+    }
+
+  //create mapper and actor for original model
+  vtkSmartPointer<vtkPolyDataMapper> mapper =
+    vtkSmartPointer<vtkPolyDataMapper>::New();
+  mapper->SetInput(polyData);
+
+  vtkSmartPointer<vtkActor> actor =
+    vtkSmartPointer<vtkActor>::New();
+  actor->SetMapper(mapper);
+  actor->GetProperty()->SetInterpolationToFlat();
+
+  //create renderer and renderWindow
+  vtkSmartPointer<vtkRenderer> renderer =
+    vtkSmartPointer<vtkRenderer>::New();
+  vtkSmartPointer<vtkRenderWindow> renderWindow =
+    vtkSmartPointer<vtkRenderWindow>::New();
+  renderWindow->AddRenderer(renderer);
+
+  renderer->AddActor(actor); //view the original model
+
+  //Compute the silhouette
+  vtkSmartPointer<vtkPolyDataSilhouette> silhouette =
+    vtkSmartPointer<vtkPolyDataSilhouette>::New();
+  silhouette->SetInput(polyData);
+  silhouette->SetCamera(renderer->GetActiveCamera());
+  silhouette->SetEnableFeatureAngle(0);
+
+  //create mapper and actor for silouette
+  vtkSmartPointer<vtkPolyDataMapper> mapper2 =
+    vtkSmartPointer<vtkPolyDataMapper>::New();
+  mapper2->SetInputConnection(silhouette->GetOutputPort());
+
+  vtkSmartPointer<vtkActor> actor2 =
+    vtkSmartPointer<vtkActor>::New();
+  actor2->SetMapper(mapper2);
+  actor2->GetProperty()->SetColor(1.0, 0.3882, 0.2784); // tomato
+  actor2->GetProperty()->SetLineWidth(5);
+  renderer->AddActor(actor2);
+  renderer->SetBackground(.1, .2, .3);
+  renderer->ResetCamera();
+
+  //you MUST NOT call renderWindow->Render() before
+  //iren->SetRenderWindow(renderWindow);
+  vtkSmartPointer<vtkRenderWindowInteractor> iren =
+    vtkSmartPointer<vtkRenderWindowInteractor>::New();
+  iren->SetRenderWindow(renderWindow);
+
+  //render and interact
+  renderWindow->Render();
+  iren->Start();
+
+  return EXIT_SUCCESS;
+}