http://www.fxguide.com/featured/the-inside-story-behind-disneys-paperman/
Step-by-step: the animation process
So how was the final animation completed? Here’s a step-by-step look at the process, as presented at
SIGGRAPH LA 2012.
CG animation – the scenes and characters are modeled, rigged and animated in the same way a typical CG animation would be completed (although with simpler models since the CG renders do not represent the final look).
Motion fields – motion fields are created on the CG animation from which the final lines will be advected. These are rendered per-frame per-element with the result being each pixel in the image having a 2D offset. The effect of this is to describe where that point on the CG model will be in the next or previous frame.
Silhouette ribbons – to preserve the ‘line’ look from traditional animation, silhouette ribbons were created for the characters. Here, a character was divided into “topologically-cylindrical components by offsetting the silhouettes perpendicular to the camera direction.” This helped ensure that lines near the character’s silhouette remained on the silhouette.
Motion paper – a paper texture advected by the motion vectors gave a temporal coherent texture to the line and paint.
Final lines and paint – using Meander, final line artists drew key drawings on top of the CG renders, relying on two techniques to then compute the non-key drawings but preserve the temporal coherence of the final-line stage.