Editing Computer animation (section)

==Animation methods==
[[File:3D dragon animation.gif|thumb|right|3D game character animated using [[skeletal animation]]]]
[[Image:Stickwalkav.gif|thumb|right|In this [[Graphics Interchange Format|.gif]] of a 2D [[Flash animation]], each 'stick' of the [[stick figure|figure]] is [[Keyframe#Animation by means of computer graphics|keyframed]] over time to create motion.]]
In most 3D computer animation systems, an animator creates a simplified representation of a character's anatomy, which is analogous to a [[skeleton]] or [[stick figure]].{{sfn|Parent|2012|pp=193–196}} They are arranged into a default position known as a [[bind pose]], or T-Pose. The position of each segment of the skeletal model is defined by animation variables, or [[Avar (animation variable)|Avars]] for short. In human and animal characters, many parts of the skeletal model correspond to the actual bones, but [[skeletal animation]] is also used to animate other things, with facial features (though other methods for [[facial animation]] exist).{{sfn|Parent|2012|pp=324–326}} The character "Woody" in ''[[Toy Story]]'', for example, uses 712 Avars (212 in the face alone). The computer does not usually render the skeletal model directly (it is invisible), but it does use the skeletal model to compute the exact position and orientation of that certain character, which is eventually rendered into an image. Thus by changing the values of Avars over time, the animator creates motion by making the character move from frame to frame.

There are several methods for generating the Avar values to obtain realistic motion. Traditionally, animators manipulate the Avars directly.{{sfn|Parent|2012|pp=111–118}} Rather than set Avars for every frame, they usually set Avars at strategic points (frames) in time and let the computer interpolate or [[tweening|tween]] between them in a process called ''[[Keyframe#Animation by means of computer graphics|keyframing]]''. Keyframing puts control in the hands of the animator and has roots in hand-drawn [[traditional animation]].{{sfn|Sito|2013|p=132}}

In contrast, a newer method called ''[[motion capture]]'' makes use of [[live action]] footage.{{sfn|Masson|1999|p=118}} When computer animation is driven by motion capture, a real performer acts out the scene as if they were the character to be animated.{{sfn|Masson|1999|pp=94–98}} Their motion is recorded to a computer using [[video camera]]s and markers and that performance is then applied to the animated character.{{sfn|Masson|1999|p=226}}

Each method has its advantages and as of 2007, games and films are using either or both of these methods in productions. Keyframe animation can produce motions that would be difficult or impossible to act out, while motion capture can reproduce the subtleties of a particular actor.{{sfn|Masson|1999|p=204}} For example, in the 2006 film ''[[Pirates of the Caribbean: Dead Man's Chest]]'', [[Bill Nighy]] provided the performance for the character [[Davy Jones (Pirates of the Caribbean)|Davy Jones]]. Even though Nighy does not appear in the movie himself, the movie benefited from his performance by recording the nuances of his body language, posture, facial expressions, etc. Thus motion capture is appropriate in situations where believable, realistic behavior and action is required, but the types of characters required exceed what can be done throughout the conventional costuming.