OpenGLBatchedPolyDataMapper: add test for overlapping cells

Rendering/OpenGL2/Testing/Cxx/CMakeLists.txt

 vtk_module_test_data(
   Data/pen_1.cur
   Data/pen_1.xcursor
+  Data/overlap_faces.vtm
+  Data/overlap_faces/overlap_faces_0_0.vtp
+  Data/overlap_faces/overlap_faces_1_0.vtp
+  Data/overlap_faces/overlap_faces_2_0.vtp
   )
 
 if (CMAKE_SYSTEM_NAME STREQUAL "Emscripten")
@@ -19,6 +23,7 @@ vtk_add_test_cxx(vtkRenderingOpenGL2CxxTests tests
   TestCameraShiftScale.cxx,NO_DATA
   TestCoincident.cxx
   TestCoincidentFloor.cxx
+  TestCompositeDataOverlappingCells.cxx,
   TestCompositeDataPointGaussian.cxx,NO_DATA
   TestCompositeDataPointGaussianSelection.cxx,NO_DATA
   TestCompositePolyDataMapper2.cxx,NO_DATA

Rendering/OpenGL2/Testing/Cxx/TestCompositeDataOverlappingCells.cxx

+// SPDX-FileCopyrightText: Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
+// SPDX-License-Identifier: BSD-3-Clause
+
+#include <vtkActor.h>
+#include <vtkCompositeDataDisplayAttributes.h>
+#include <vtkCompositePolyDataMapper.h>
+#include <vtkFeatures.h>
+#include <vtkInformation.h>
+#include <vtkNew.h>
+#include <vtkProperty.h>
+#include <vtkRenderWindow.h>
+#include <vtkRenderWindowInteractor.h>
+#include <vtkRenderer.h>
+#include <vtkSmartPointer.h>
+#include <vtkStreamingDemandDrivenPipeline.h>
+#include <vtkXMLMultiBlockDataReader.h>
+
+#include <vtkLogger.h>
+#include <vtkRegressionTestImage.h>
+#include <vtkTesting.h>
+
+/**
+ * The purpose of this test is to make sure that we always have the same image produced by the
+ * composite polydata mapper if we do multiple render call, it was previously not the case when
+ * a multiblock have some overlap between these blocks.
+ */
+int TestCompositeDataOverlappingCells(int argc, char* argv[])
+{
+  vtkDebugWithObjectMacro(nullptr, "Load the multiblock.");
+
+  vtkNew<vtkTesting> testing;
+  testing->AddArguments(argc, argv);
+
+  std::string filename = testing->GetDataRoot();
+  filename += "/Data/overlap_faces.vtm";
+
+  vtkNew<vtkXMLMultiBlockDataReader> reader;
+  reader->SetFileName(filename.c_str());
+  reader->Update();
+
+  vtkDebugWithObjectMacro(nullptr, "Setup everything to be able to render with VTK this data");
+
+  vtkSmartPointer<vtkRenderWindow> win = vtkSmartPointer<vtkRenderWindow>::New();
+  vtkSmartPointer<vtkRenderWindowInteractor> iren =
+    vtkSmartPointer<vtkRenderWindowInteractor>::New();
+  vtkSmartPointer<vtkRenderer> ren = vtkSmartPointer<vtkRenderer>::New();
+  win->AddRenderer(ren);
+  win->SetInteractor(iren);
+  win->SetSize(400, 400);
+
+  vtkSmartPointer<vtkCompositePolyDataMapper> mapper =
+    vtkSmartPointer<vtkCompositePolyDataMapper>::New();
+  mapper->SetInputConnection(reader->GetOutputPort());
+  mapper->SelectColorArray("SpatioTemporalHarmonics");
+
+  vtkSmartPointer<vtkActor> actor = vtkSmartPointer<vtkActor>::New();
+  actor->SetMapper(mapper);
+  ren->AddActor(actor);
+
+  vtkDebugWithObjectMacro(nullptr,
+    "Everything should be setup now, do multiple render call and check that we always "
+    "have the same result.");
+
+  int status = EXIT_SUCCESS;
+  int numberOfRenderCalls = 10;
+
+  for (int i = 0; i < numberOfRenderCalls; i++)
+  {
+    reader->GetOutputInformation(0)->Set(vtkStreamingDemandDrivenPipeline::UPDATE_TIME_STEP(), i);
+    reader->Update();
+    int retVal = vtkRegressionTestImageThreshold(win, 0.05);
+    if (retVal == vtkRegressionTester::DO_INTERACTOR)
+    {
+      iren->Start();
+      // if we test this executable we don't want to do multiple render call, skip.
+      break;
+    }
+
+    if (retVal == vtkRegressionTester::FAILED)
+    {
+      vtkErrorWithObjectMacro(
+        nullptr, << "The " << i
+                 << "th image produced is wrong, we should always have the same image produced.");
+      status = EXIT_FAILURE;
+      break;
+    }
+  }
+
+  return status;
+}

Rendering/OpenGL2/Testing/Data/Baseline/TestCompositeDataOverlappingCells.png.sha512

+e56901c48fd5a3bc110cc876a83faf0cf4c6f22e8542812e62e9377510bf5dc7a9ff9f72ca3f2f9a08030f153740db367f128d83f19191beffde55c54e09a28e

Testing/Data/overlap_faces.vtm.sha512

+3194f0d02f60d93f72b7591a49aa0eeacf7d8d560eb6a88d012ab5790e8b680a6164ea5cc33b5c0793017431439fba1b94f270d779b73d3294b8ddee8c3fcc0d

Testing/Data/overlap_faces/overlap_faces_0_0.vtp.sha512

+1a4f71ffcd5b4affe75447f01eb811936c0b5c72b63f6d1ffac7898699d5b6e435f3127e0b507f0a6407e047177f651400e94aa27f98c84d9fe620daf37cc0f7

Testing/Data/overlap_faces/overlap_faces_1_0.vtp.sha512

+83f1f8ea810227c728a194e392ed464c8fcbd07f38427749136fdcf8c561b6919b1d2f334113bf67cf05086a94148b1e4f8b243d87ac677ef4b23dc5de273215

Testing/Data/overlap_faces/overlap_faces_2_0.vtp.sha512

+4cc78a1e91fe9a6bc4d004457de40aae709c28ea0a98ee6ddb9353bcec164d1bc4ffb028f59a6e445840672011647ff3f6f7e881fcecb7f3079cb84d5ea6fbf3