vtk Representation: reset slice viz and position when volume is added later.

smtk/extension/paraview/server/vtkSMTKResourceRepresentation.cxx

@@ -290,12 +290,26 @@ int vtkSMTKResourceRepresentation::RequestData(
         this->SliceXY->SetSliceMode(vtkImageSliceRepresentation::XY_PLANE);
         this->SliceYZ->SetSliceMode(vtkImageSliceRepresentation::YZ_PLANE);
         this->SliceXZ->SetSliceMode(vtkImageSliceRepresentation::XZ_PLANE);
+
+        // when slice reps were hidden, their default slice is zero - reset
+        if (this->SliceXY->GetSlice() == 0 && this->SliceYZ->GetSlice() == 0 &&
+          this->SliceXZ->GetSlice() == 0)
+        {
+          int dimensions[3];
+          sliceVolume->GetDimensions(dimensions);
+          this->SliceXY->SetSlice((dimensions[2] - 1) / 2);
+          this->SliceYZ->SetSlice((dimensions[0] - 1) / 2);
+          this->SliceXZ->SetSlice((dimensions[1] - 1) / 2);
+        }
         this->SliceXY->SetInputArrayToProcess(
           0, 0, 0, vtkDataObject::FIELD_ASSOCIATION_POINTS, scalarName.c_str());
         this->SliceYZ->SetInputArrayToProcess(
           0, 0, 0, vtkDataObject::FIELD_ASSOCIATION_POINTS, scalarName.c_str());
         this->SliceXZ->SetInputArrayToProcess(
           0, 0, 0, vtkDataObject::FIELD_ASSOCIATION_POINTS, scalarName.c_str());
+        this->SliceXY->SetVisibility(true);
+        this->SliceYZ->SetVisibility(true);
+        this->SliceXZ->SetVisibility(true);
       }
     }
     else