Understanding how motion works and the control methods used within the human body will help us better understand animation workflows when using armatures/rigs. It is important to note that there is no one right answer or solution and animators will typically use a combination of tools, references and mathematics to help them achieve their desired results be they realistic or stylised.

Inverse Kinematics (IK)

These work by taking into account each connected ‘bone’ and their weight and connections to each other for example when you raise your foot off the ground the knee, pelvis and overall body weight readjust to keep you balanced and when we are working with IK rigs each motion will effectively pull and reposition each connected joint.

Every previous bone and connection within the chain is affected, we can set anchor/fulcrum points to essentially pin these connection points to a surface if needed.

Forward Kinematics (FK)

Forward Kinematics translates the positional and rotational values of a selected point around an anchor point (pivot point). Any bones or objects attached to this bone also move. FK is a chain system whereby only bones following the selected bone are affected; preceding bones in the chain are unaffected by any value changes.

This gives animators a lot more manual control however, it will make the animation process take longer as each bone will need more manual adjustments as the bones carry minimal influence over the whole rig before the selection point.

Animators may choose to keep arms and hands in FK mode whilst keeping the rigs feet and body in IK mode as animators will want feet to remain planted and give a sense of weight and balance when moving which is harder to achieve through FK as its a slower process.