Wow, i can't believe how reactive you guys are ! Thanks so much for your feedback.
It looks like the Two Point Perspective is the tool i need, thanks for poiting it out.
Although it could be triggered by the send_action command, to control it precisely in ruby afterwards is still problematic : how can i control the amount of shift to apply in ruby ?
The reason i want to do it ? I'm developping a video projector simulator plugin, and i would like the user to be able to 'see' from the projector perspective.
On the image below, i put an image of a projector with a vertical lens shift of 100%. You can see what the projection cone looks like, it is off centered, and i would need to place a camera, and apply two point perspective to match the projection of the video projector.

I hope this clarifies what i want to achieve 