Allen and Davis: Old footage was used as a reference for the modern dancer. The modern dancer danced to match the old footage exactly. The new footage was added and blended to match and appear real, a la Forrest Gump. The new film was transferred to appear old, like the original.
Humble: They shot a dancer doing the new moves and did head replacement with Gene Kelly's head. The move where he grabs the lamp post and his legs bend over his body was done by using two different shots one for his upper torso and one for his legs. Then they morphed them together.
the real moves
Singing and breakdancing to the classic Singin' in the Rain(remixed by maestro musicians Mint Royale), dance legend Gene Kelly performs some breathtakingly modern moves in a new spot for VW Golf, thanks to postproduction magic from The Moving Picture Company in London. Stink directors NE-O re-created the famous dance sequence from the 1952 flick at Shepperton Studios with MPC Visual Effects Supervisor Alex Lovejoy on hand. Involved in the project from the outset, Lovejoy was convinced the impossible could happen. "It was certainly a huge challenge to make this spot believable but we all felt that we could do the concept justice."
MPC's task was basically a complex noggin replacement that transplanted Kelly's Old School head from the original film, onto the bodies of three nimble-footed poppers: David "Elsewhere" Bernal, Crumbs and Jay Walker. Lovejoy began by matching the set, dancers and lighting as near to perfect to the original film sequence as possible, thereby allowing him to concentrate solely on the look and movement of the head replacements: "We checked the camera moves by doing live split screens with the original [film] shots to successfully integrate Gene's head onto the dancers bodies," Lovejoy explains. "Then we shot clean plates of the backgrounds that followed the same camera moves to help remove the dancers' heads."
Back at the facility, MPC had a difficult job creating a modern day Gene Kelly. To begin, an HD resolution version of Singin' in the Rain was acquired to capture original sequences with Kelly dancing. Inferno became the main compositing tool although Combustion was fired up for rotoscoping and paint work duties. With some sequences 15 seconds in length MPC had to reverse, frame-cut and morph together Kelly's head to match that of the dancers' moves.
A number of smart effects layered onto the work also helps sell the illusion, some emulating the original film sequence. "In the studio we shot rain and splash effects against black, then placed them onto the head composites to finesse the look," reveals Lovejoy. "Plus the shirt and tie animation was particularly complex because it required very specific hand animation to blend with the new head. This was achieved using warping and tracking tools in inferno and, in some cases, was painted in by hand."
As a final touch MPC re-transferred the commercial back to film before grading the negative to become the final master. This process of re-shooting to film helps blend the composites and thus gives an "organic" feel to the final print.