how did cameron manage to combine live-action scenes with computer-generated scenes

James Cameron managed to combine live-action scenes with computer-generated (CG) scenes in his film "Avatar" through several innovative technologies and techniques. He used motion capture technology where actors wore special suits with markers that were tracked by cameras to record their movements. Along with these suits, actors wore helmets fitted with small high-definition cameras that captured their facial expressions in great detail. This allowed animators to transfer realistic human emotions and movements to the CG characters, known as the Na'vi, creating what Cameron referred to as "performance capture" rather than just motion capture. Cameron also utilized a virtual camera system and his own Fusion Camera System which allowed him to direct and see CG characters and digital environments in real time while shooting live-action. This was a breakthrough because, unlike traditional green-screen methods where CG is added in post-production, Cameron could see the combined live-action and CG scenes as they were being filmed. The SimulCam system was critical here — it tracked the live-action camera's position on the motion capture stage and superimposed CG elements, allowing Cameron and the actors to interact with the CG environment and characters on set. This gave Cameron precise control over framing and integrated the two elements seamlessly. The Fusion Camera System involved two cameras that mimicked human binocular vision for natural 3D effects, and the entire process was carefully choreographed so that live-action footage and CG elements were composited together live and refined in real time. In summary, Cameron's approach combined performance capture, virtual camera technology, the Fusion Camera System, and the SimulCam system to integrate live-action and computer- generated scenes in a highly immersive and controlled way, achieving seamless visual storytelling.