There was a time when actors have to do everything in real in order to displace any scene in the movie. Now time has changed and every thing with become so easy because of the technology and software available now.
Now its not mandate to be available on same place to show in the movie, thanks to VFX technology. We can easily shoot the scene somewhere else and edit with another place in the movie. Even now director using this technology to shoot the scenes without the actor and actress and put them into the scene separately. Here we have one of the example where where you can see how actress Kajal Aggarwal shots kissing scene with the actor and post shooting how director insert Actor’s face and make this scene in real.