To give the characters more life in Teenage Mutant Ninja Turtles, Pablo Helman of Industrial Light & Magic decided it would be best to capture the facial expressions of the actors conducting the motion capture work.
Helman would then capture those performances, turn them into digital assets, and then bring in an animator to reinterpret the digital performances.
To give Leonardo, Raphael, Donatello, and Michelangelo even more facial expressions, the production team placed two high-definition cameras on each actor’s face in addition to the various sensors placed around their bodysuits to capture the desired shots.
In a 2014 Wired Design FX video on the production of the movie, Helman revealed that he and his team developed a technology called Performance Retargeting that would allow all four actors to be on set at the same time and give the director a chance to direct in real-time.