These are some compositing shots I worked on, while I was at Legend 3D.
I was only given some of the shots from The Smurfs and The Amazing Spider-Man.
The same workflow carried through on all the other movies I worked. The last few movies I worked on were The Man of Steel, The Smurfs II, and the Amazing Spider-Man 2.
As far as the workflow, back then, the compositors would work off of the stereoscopic 3D renders, from the company's proprietary software. There would be artifacts and stretching that would occur, to add depth (think of UV's stretching), depending on what's forward to the viewer, and what's back.
This was something I wasn't sure if they relate with the other 3D stuff that I've done (this is a different kind of 3D). The compositing side of it is kind of relates with texturing a bit, masking out certain areas, paint patches, color channels, etc. We would clean up and polish the shots in stereo 3D, making sure that they would match with the 2D version.