Cloud Atlas is not only a fantastic movie, it was a great team to work with at Scanline VFX. We made a lot of nice shots, and I have to say, it was fun.
I have done a couple of shots in an underwater tunnel, combining live action greenscreen shots and full CG backgrounds. The main shot I was handling was the Entrance shot of the clones, walking into a slaughter ship. The shot is featured in the December Issue of Cinefex. I took several greenscreen elements and placed them on cards in Nuke to create around 250 avatars. All the dust elements and Volume lighting was comped in using a combination of deep compositing and faked card setups in Nuke. The original camera move for the foreground action was also altered by me in Nuke, as the directors wanted to extend the shot and see more of the ship. Take a look at the making of here