Hi Fan,
You seem to be newbie at understanding what level of information is
required to debug stuff locally, let alone remotely as you are
expecting the community to do here. We aren't clairvoyant.
If you get a seg fault the first thing you do is use a debugger to get
a stack trace. This stack trace will give you your first clue as to
what the problem might be. Without this information you or anybody
else will be able to divine what might be amiss.
Also if you want help you'll need to provide more info, like OSG
version, OS version, compiler used.
The OSG also doesn't negatively have a citygml support, so you'd need
to tell us about where you are getting this from, and whether it's
know at all whether you readNodeFile is generating a valid file or
not.
Robert.