Hey people!

I know this is another 2A question, but Ive wanted to know how to do this effect for a while now, which now I have the opportunity to do it, and I have seen it done on other sites but this is one that I could think of right now. Im sure we've all seen it but take a look at the oakley intro.... http://www.2advanced.com/oakley/

See at the end when the symbol kind of masks over the not so detailed one, into a beveled/embossed "O". How is that done?

Any help is much appreciated.