Please note a significant change in VTK.
In the changeset from Merge Request !11993, the inclusion of <iostream> has been removed from a core header. This change previously caused global constructors to be triggered in every downstream translation unit.
As a result, applications that link to VTK can no longer assume that objects such as cin, cout, and cerr are automatically available. To ensure compatibility with this update, applications must now explicitly #include <iostream> and use the std namespace when referring to standard I/O streams, such as std::cin, std::cout, and std::cerr.