Hasta La Motion!

I was wondering what was the best method for 2D to 3D conversion.
Rotoscoping I get that.
But after rotoscoping is it better to make a 3D environment and project everything on card placed in z depth using a rig of camera (in that case, I don’t have the camera info of the shot)
Or is it better to make a displacement map in 2D, use idistort and a transform between the left and right views?.

I tried both and I have some issues with the 3D environment. For example, if I project every layer rotoscoped on differents cards, how do I do a displace geo on a projection?
Well if somenone can show me a tut how to make 2D to 3D conversion it would be awesome

thanks!