Setting IK Keyframe Constraints

When setting up a hierarchy chain, the parent is usually the part that is at a logical point of rotation. For example, in the case of a leg, the parent would be the thigh, as it rotates from the hip and its children would be the shin and foot that will always follow.

However, sometimes you come across a situation where you need the movement to stem from the child, such as in the case of a ballerina, where the shin and thigh rotation follow the position of the foot. In order to keep the foot from gliding around, making the kinds of secondary movements that children do, you need to nail the foot in place and constrain its orientation (rotation). Sometimes this constraint needs to be held for several frames.