Updated test to new ivar to turn off auto adjust sample distance

Rendering/Volume/Testing/Cxx/TestSmartVolumeMapperWindowLevel.cxx

@@ -627,12 +627,23 @@ int TestSmartVolumeMapperWindowLevel(int argc,
   vtkNew<vtkSmartVolumeMapper> mapper1;
   mapper1->SetInputConnection(reader->GetOutputPort());
   mapper1->SetRequestedRenderModeToDefault();
+
   vtkNew<vtkSmartVolumeMapper> mapper2;
   mapper2->SetInputConnection(reader->GetOutputPort());
+
   vtkNew<vtkSmartVolumeMapper> mapper3;
   mapper3->SetInputConnection(reader->GetOutputPort());
   mapper3->SetRequestedRenderModeToRayCast();
 
+#ifdef VTK_OPENGL2
+  mapper1->SetAutoAdjustSampleDistances(0);
+  mapper1->SetInteractiveAdjustSampleDistances(0);
+  mapper2->SetAutoAdjustSampleDistances(0);
+  mapper2->SetInteractiveAdjustSampleDistances(0);
+  mapper3->SetAutoAdjustSampleDistances(0);
+  mapper3->SetInteractiveAdjustSampleDistances(0);
+#endif
+
   vtkNew<vtkColorTransferFunction> ctf;
   ctf->AddHSVPoint(1.0, 0.65, 1.0, 1.0);
   ctf->AddHSVPoint(256, 0.95, 0.098, 1.0);