He made it clear that he was after a very natural, real effect... he wanted to keep the emotional connection between the viewer and the image intact. At all costs, he wanted to avoid any kind of ‘plastic’ look.”

The Gradient FX team persuaded Milk to consider a different approach. Thomas Tannenberger, the project’s VFX supervisor, explains: “We showed [Milk] our work with creatures and organic surfaces for other projects. We suggested all-CG, relying heavily on motion-capture to get the liveaction feel he was after.”

Right from the start, the team realized it would need two layers of motion capture: one for the body, and another for the lips. “We agreed that the animation should capture a heavy, clumsy movement,” says Tannenberger.

“Chris cast a tall, heavy-set actor whose mass and movements would translate into the bulbous heart we would build in CG.”

The team turned to specialist Phase Space for the motion-capture work, which captured the actor’s motions as he lumbered around. Tan says that even finding the actor proved fraught. “The entire project was approached as a live-action shoot,” he says.

“Every aspect remained under Chris’ control. This included the casting of the mo-cap actor, which was not completed until the day before the mo-cap session.

"Due to the size requirements for the role, we had to fabricate a custom mo-cap suit for him overnight, and source a stage, which because it was at the eleventh hour, turned out to simply be an empty building. In the end it all came together for a relatively uneventful mo-cap session.”

Phase Space also performed a close-up motion-capture on Cee-lo’s face as he sang the song’s lyrics, focusing in particular on the lips but also aiming to capture the overall movements of his face’s contours.

The Gradient FX team then turned to Image Metrics, who tracked the motion-capture and delivered the animation back to the team so that it could be integrated with the rig.