fix an OpenGL2 issue impacting slicer and add test

There were two issues impacting slicer. ImageMappers
were not honoring their DisplayLocation property value
and 2d mappers were setting zbufer values on 100%
transparent pixels.

Added a test from Max Smolens that tests for both of these
issues to prevent future regressions.

Author: martinken

Rendering/Core/Testing/Cxx/CMakeLists.txt

@@ -58,6 +58,7 @@ vtk_add_test_cxx(${vtk-module}CxxTests tests
   TestGradientBackground.cxx
   TestHiddenLineRemovalPass.cxx
   TestHomogeneousTransformOfActor.cxx
+  TestImageAndAnnotations.cxx,NO_DATA
   TestInteractorStyleImageProperty.cxx,NO_VALID
   TestInteractorTimers.cxx,NO_VALID
   TestLabeledContourMapper.cxx

Rendering/Core/Testing/Cxx/TestImageAndAnnotations.cxx

@@ -0,0 +1,133 @@
+#include <vtkCornerAnnotation.h>
+#include <vtkImageData.h>
+#include <vtkImageMapper.h>
+#include <vtkInteractorStyleImage.h>
+#include <vtkProperty2D.h>
+#include <vtkRenderWindow.h>
+#include <vtkRenderWindowInteractor.h>
+#include <vtkRenderer.h>
+#include <vtkSmartPointer.h>
+#include <vtkTextProperty.h>
+
+#include <vtkTestUtilities.h>
+#include <vtkRegressionTestImage.h>
+
+namespace
+{
+
+vtkSmartPointer<vtkImageData> CreateColorImage(unsigned int dim, bool transparent)
+{
+  vtkSmartPointer<vtkImageData> image = vtkSmartPointer<vtkImageData>::New();
+  image->SetDimensions(dim, dim, 1);
+  image->AllocateScalars(VTK_UNSIGNED_CHAR, 4);
+
+  for (unsigned int x = 0; x < dim; x++)
+    {
+    for (unsigned int y = 0; y < dim; y++)
+      {
+      unsigned char* pixel = static_cast<unsigned char*>(image->GetScalarPointer(x, y, 0));
+      pixel[0] = 255;
+      pixel[1] = 0;
+      pixel[2] = 255;
+      pixel[3] = transparent ? 127 : 255;
+      }
+    }
+
+  return image;
+}
+
+vtkSmartPointer<vtkActor2D> CreateImageActor(int dim, int displayLocation, bool transparent)
+{
+  vtkSmartPointer<vtkImageData> colorImage = CreateColorImage(dim, transparent);
+
+  vtkSmartPointer<vtkImageMapper> imageMapper = vtkSmartPointer<vtkImageMapper>::New();
+  imageMapper->SetInputData(colorImage);
+  imageMapper->SetColorWindow(255);
+  imageMapper->SetColorLevel(127.5);
+
+  vtkSmartPointer<vtkActor2D> imageActor = vtkSmartPointer<vtkActor2D>::New();
+  imageActor->SetMapper(imageMapper);
+  imageActor->SetPosition(dim, 0);
+  imageActor->GetProperty()->SetDisplayLocation(displayLocation);
+
+  return imageActor;
+}
+
+} // namespace
+
+int TestImageAndAnnotations(int argc, char *argv[])
+{
+  // Setup renderer
+  vtkSmartPointer<vtkRenderer> renderer = vtkSmartPointer<vtkRenderer>::New();
+
+  // Setup render window
+  vtkSmartPointer<vtkRenderWindow> renderWindow = vtkSmartPointer<vtkRenderWindow>::New();
+  renderWindow->SetSize(600, 600);
+  renderWindow->AddRenderer(renderer);
+
+  // Setup render window interactor
+  vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor =
+    vtkSmartPointer<vtkRenderWindowInteractor>::New();
+  vtkSmartPointer<vtkInteractorStyleImage> style =
+    vtkSmartPointer<vtkInteractorStyleImage>::New();
+  renderWindowInteractor->SetInteractorStyle(style);
+
+  // Setup corner annotation
+  vtkSmartPointer<vtkCornerAnnotation> cornerAnnotation =
+    vtkSmartPointer<vtkCornerAnnotation>::New();
+  cornerAnnotation->SetLinearFontScaleFactor(2);
+  cornerAnnotation->SetNonlinearFontScaleFactor(1);
+  cornerAnnotation->SetMaximumFontSize(20);
+  cornerAnnotation->SetText(0, "background/opaque"); // lower left
+  cornerAnnotation->SetText(1, "foreground/opaque"); // lower right
+  cornerAnnotation->SetText(2, "background/transparent"); // upper left
+  cornerAnnotation->SetText(3, "foreground/transparent"); // upper right
+  cornerAnnotation->GetTextProperty()->SetColor(1, 1, 1);
+
+  renderer->AddViewProp(cornerAnnotation);
+
+  // Setup images
+  const unsigned int Dim = 300;
+  {
+    // lower left: background/opaque
+    bool transparent = false;
+    vtkSmartPointer<vtkActor2D> imageActor = CreateImageActor(Dim, VTK_BACKGROUND_LOCATION, transparent);
+    imageActor->SetPosition(0, 0);
+    renderer->AddActor(imageActor);
+    }
+  {
+    // lower right: foreground/opaque
+    bool transparent = false;
+    vtkSmartPointer<vtkActor2D> imageActor = CreateImageActor(Dim, VTK_FOREGROUND_LOCATION, transparent);
+    imageActor->SetPosition(Dim, 0);
+    renderer->AddActor(imageActor);
+  }
+  {
+    // upper left: background/transparent
+    bool transparent = true;
+    vtkSmartPointer<vtkActor2D> imageActor = CreateImageActor(Dim, VTK_BACKGROUND_LOCATION, transparent);
+    imageActor->SetPosition(0, Dim);
+    renderer->AddActor(imageActor);
+  }
+  {
+    // upper right: foreground/transparent
+    bool transparent = true;
+    vtkSmartPointer<vtkActor2D> imageActor = CreateImageActor(Dim, VTK_FOREGROUND_LOCATION, transparent);
+    imageActor->SetPosition(Dim, Dim);
+    renderer->AddActor(imageActor);
+  }
+
+  renderer->ResetCamera();
+
+  // Render and start interaction
+  renderWindowInteractor->SetRenderWindow(renderWindow);
+  renderWindowInteractor->Initialize();
+
+  int retVal = vtkRegressionTestImage( renderWindow );
+  if ( retVal == vtkRegressionTester::DO_INTERACTOR)
+    {
+    renderWindowInteractor->Start();
+    }
+
+  return !retVal;
+}

Rendering/Core/Testing/Data/Baseline/TestImageAndAnnotations.png.md5

@@ -0,0 +1 @@
+27dff115bc20d630b32da6da2581c199

Rendering/OpenGL2/glsl/vtkPolyData2DFS.glsl

@@ -42,6 +42,12 @@ void main()
 
   //VTK::Color::Impl
   //VTK::TCoord::Impl
+
   //VTK::DepthPeeling::Impl
   //VTK::Picking::Impl
+
+  if (gl_FragData[0].a <= 0.0)
+    {
+    discard;
+    }
 }

Rendering/OpenGL2/vtkOpenGLImageMapper.cxx

@@ -607,6 +607,9 @@ void vtkOpenGLImageMapper::RenderData(vtkViewport* viewport,
     return;
     }
 
+
+  this->Actor->SetProperty(actor->GetProperty());
+
   // Make this window current. May have become not current due to
   // data updates since the render started.
   window->MakeCurrent();
@@ -691,9 +694,7 @@ void vtkOpenGLImageMapper::DrawPixels(vtkViewport *viewport, int width, int heig
 
   this->Actor->GetTexture()->SetInputData(id);
 
-  glDisable(GL_DEPTH_TEST);
   this->Actor->RenderOverlay(viewport);
-  glEnable(GL_DEPTH_TEST);
   id->Delete();
 }