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Rigging

By Default, a character created in computer animation is simply a stiff sculpture that holds the shape provided by the user. To get liflelike motion of a character, All of the motion mechanics must be described by the animator to the computer in a complicated process called rigging.

To begin with, an artist will determine where the joints of the character should be placed inside the character's geometry. Placement of the joints is very important to get the character's body to deform in the right place. Once all of the joints are placed, The joints are givin limitations to their rotation. This ensures that the character's elbows do not bend the wrong way, and the character can move in a predictable way.

Next the joints or bones are attached to the geometry of the character in a step called "binding". In this stage, the geometry is painted with weight maps that control how much each bone has influence to the surrounding geometry of the character. This ensures that when the knee bends, that the character's neck or hands are not moved along with this transformation.

Once all of this is done, the animator can rotate the joints to pose the character but It is still a very tedious process. To speed up the posing, special controlers called Inverse Kinematics (or IK for short) are added to the joints of the arms, legs, spine, etc. so that moving a character's foot IK handle will adjust the rotation of all of the joints in the leg so that the pose can be achieved correctly and quickly.

This stage however leaves the character with a lot of complicated IK chains that are necessary but difficult to deal with because of the complexity of IK handles needing to be moved to get the character to animate. At this stage, more work can be done to simplify the Character setup. To do this, simple squares and circles in 3d space can be positioned near key controllers, and The controlers are programmed to respond to the movement of these controlers. At the same time, certain controlers can be given attributes like "finger bend" and programmed to move some joints that are not controlled by IK (like the fingers).

Once all of this is done, the character can be handed off to an animator who can position the controls to achieve the spectacular poses needed in animtation. Because of the complex controls, a pose can be achieved in seconds as opposed to minutes or longer.