Motion capture refers to recording actions of human actors, and using that information to animate digital character models in 2D or 3D computer animation. When it includes face and fingers or captures subtle expressions, it is often referred to as performance capture. In many fields, motion capture is sometimes called motion tracking, but in filmmaking and games, motion tracking usually refers more to match moving.
The actors in these types of VFX movies wear body suits that use a performance capture type of system that allows multiple cameras to record the small details like facial movements and specific body movements as well. Check out the below video that shows a glimpse of the behind the scenes work from Dawn of the Planet of the Apes.
Check out some behind the scenes VFX on the creation of the creature Gollum from The Lord of the Rings trilogy. Gollum is a mysterious cave-dwelling creature corrupted by the power of the ring. His digital character was created by New Zealand-based visual effects company Weta Digital.
In this Nature Video they go behind the scenes with Weta’s Senior Visual Effects Supervisor, Joe Letteri, who reveals the technology they used to make Gollum’s eyes, skin and movements look believable.