Currently QmitkSlicesInterpolator::Initialize requires a list of slice navigation controllers.
The QmitkSlicesInterpolator is initialized inside QmitkSegmentationView::RenderWindowPartActivated, where the three slice navigation controllers are retrieved from the "axial", "sagittal" and "coronal" render windows.
This is problematic in two ways:

1. QmitkSegmentationView::RenderWindowPartActivated still uses render window names, which conflicts with the MxNMultiWidget (see T25595: [Multi widget] Make classes work with the new render window access)
2. the render window is required inside QmitkSlicesInterpolator which is retrieved from the slice navigation controllers
   • however, QmitkSlicesInterpolator seems to be the only class that retrieves the render window / base renderer from the slice navigation controller, which hinders us to remove the base renderer variable (and its accessors) from the slice navigation controller (see https://phabricator.mitk.org/source/mitk/browse/develop/Modules/Core/include/mitkSliceNavigationController.h$344-349)

This could easily be solved together with the parent task.