The history of Rotoscoping, the animation technique behind Amazon’s "Undone"
Undone Combines Live Action and Animation | Prime Video
Rotoscope Frame Based Animation Technique [Example]
How To: Traditional Rotoscoping Animation
Rotoscoping is an animation technique that animators use to trace over motion picture footage, frame by frame, to produce realistic action. Originally, animators projected photographed live-action movie images onto a glass panel and traced over the image. This projection equipment is referred to as a rotoscope, developed by Polish-American animator Max Fleischer. This device was eventually replaced by computers, but the process is still called rotoscoping.