A sort of follow up/related question to this.
I\'m trying to get a grip on a large code base that has hundreds and hundreds of classes and a large inheritance hierarchy.
A good UML tool should do the trick.
Here is a list of generic UMl tools: http://en.wikipedia.org/wiki/List_of_UML_tools
There are lots out there, all with varying feature sets. Try playing with a few to see if you get the output you desire. If they free ones fail you, you might have to shell out for a good commercial grade UML tool
I've had most success with valgrind and kcachegrind to do this. You run valgrind against your debugging binary, perform whatever actions your interested in, then import the output into kcachegrind to see everything you'd ever want to know about who called what, how often, and when. Plus, because your doing it dynamically, it catches cases that static analysis likely wont.
I've also had some success using Enterprise Architect's reverse engineering features, although this doesn't end up nearly as nicely (but you get a workable UML model which is nice!).
And finally, a tool called "Understand". This is pretty good at static OO analysis, but I think quite pricey and not that widely used.
What's your definition of 'main vein'? You either want a graph reducer or skeletizer (you could find or write one and apply it to what Doxygen and the rest produce) or, 'main vein' has something to do with the function of the code and, I don't think an automated tool can help you with that. Unless you can point out to it 'These are the important bits that do input and output, show me only elements that are one or two steps away from the paths between these'. Hum, sounds like a cool tool to write :)
... the inheritance hierarchy, in some kind of collapsible view.
again, a sweet idea for a tool!