David, thanks for the suggestions. I spent the weekend trialing the programs.
Doxygen seems to be the most comprehensive of the 3, but it still leaves some things to be desired in regard to callers of methods.
All 3 seem to have problems with C++ templates to varying degrees. CC-Rider simply crashed in the middle of the analysis and CodeDrawer does not show many of the relationships. Doxygen worked pretty well, but it too did not find and show all relations and instead overwhelmed me with lots of macro references until I filtered them out.
So, maybe I should clarify "large codebase" a bit for eventual other suggestions: >100k lines of code overall spread out over more than 100 template files plus several actual class files pulling it all together.
Any other tools out there, that might be up to the task and could do better (more thoroughly)? Oh and specifically: anything that understands IDL and COM interfaces?