Yes, basically. For open-source projects where google retains the copyright you don't need special permission (it is part of your job, basically). For personal stuff or where you wish to retain the copyright then you will need it assigned to you.
[0] 'Moreover, some states, including California and Illinois, have laws that limit the effectiveness of assignment-of-inventions agreements where the invention was created outside the inventor's employment with the company.' -- http://www.masudafunai.com/showarticle.aspx?Show=5942