Inverse kinematic animation

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Inverse kinematic animation (IKA) refers to a process utilized in 3D computer graphic animation, to calculate the required articulation of a series of limbs or joints, such that the end of the limb ends up in a particular location. In contrast to forward kinematic animation, where each movement for each component must be planned, only the starting and ending locations of the limb are necessary.

For example, when one wants to reach for a door handle, their brain must make the necessary calculations to position his limbs and torso such that the hand locates near the door. The main objective is to move the hand but the many complex articulations of several joints must occur to get the hand to the desired location. Similarly with many technological applications, inverse kinematic mathematical calculations must be performed to articulate limbs in the correct ways to meet desired goals.

One example where inverse kinematic calculations are often essential is robotics, where an operator wants to position a tool using a robot arm but certainly doesn't want to manipulate each robot joint individually. Other applications include computer animation where animators may want to operate a computer generated character, but find it impossibly difficult to animate individual joints. The solution is to model the virtual joints of the puppet and allow the animator to move the hands feet and torso, and the computer automatically generates the required limb positions to accomplish this using inverse kinematics.

Key to the successful implementation of inverse kinematics is animation within constraints: computer characters' limbs must behave within reasonable anthropomorphic limits. Similarly, robotic devices have physical constraints such as the environment they operate in, the limitations of the articulations their joints are capable of, and the finite physical loads and speeds at which they are able to operate.

See also: Inverse kinematics