Hi, don’t know of any plugin that would do that. I suspect you need a clean plate without anyone on the seat, then (on location) greenscreen the actors with the seat. Mask out the girl on a separate layer, go into Photoshop and make the long version of the seat and shadow. In your main comp set up perspective guidelines along the seat, animate the girl section (in 3D?) to match the perspective guidelines while revealing the Photoshoped image. Well that would be a starting point.