> I'm very puzzled with the handshake of JFK and Tom Hanks ("Forrest Gump"
> I know about blue screen technique but I can't imagine how can an actor
> follow the exact trajectory of his body, his hands, etc. Can you explain me
I remember seeing some program on the special effects done in
Forrest Gump. (It was quite some time ago, so I may be totally
out to lunch here.) As I recall it, Hanks studied the clip of
Kennedy shaking hands with someone for a while, and then tried
to mimick the motions of the guy whose hand he was shaking. They
had to due a number of takes before they got it right. So it's
just trial and error.