Buildiing RPM from a local directory

[firelex]

Hello, all!
My problem is:
I have some stuff in my directory
(e.g. /home/eagon/product )
Is there any possibility to build a rpm of it without copying all the things to there appropriate places? I mean all the files in rpm should be in certain directories. (And most *.spec files that saw define also absolute paths for each file). Could I e.g. organize in my /home/eagon/product directory everything so that it looks like it were on the right place
(e.g. /home/eagon/product/usr/lib/...
/home/eagon/product/usr/local/book/...
)
and start building from /home/eagon/product ?

Or if I get all things into an *.tgz or *.tar how can I tell the rpm in a *.spec - file where every file should be placed?

Thanks