What is overlapping action?
The movement of the different parts of a living creature do not occur at the same time; things start, move and stop at different points and move at different rates. In order to achieve this lifelike actions it is necessary to create time lagss between these seperate actions making the movement of the individual elements overlap. We call this overlapping action.
Overlapping action is often down to complexity of the structure: the various materials it’s made of, the nature of locomotion (the action), the effects of the natural forces upon the different parts (hair, arms, clothing and solid objects), the way in which these parts are connected, and a wholw host of other variables.
An object, even one with a low degree of complexity, will demonstrate varying levels of dynamics throughout its structure during its natural motion. The separate parts of things nearly always move at different times and at different speeds. Animating a character as complex as a horse, for example, will by necessity demand a high degree of variable dynamic actions due to the nature of its physiognomy (appearance) and the complexity of its mode of action (locomotion).
Its these little variations in actions that will make your animation convincing and create the performance you are trying to deliver.
Primary, Secondary and Tertiary Action
As animators, we begin our work by adding layer upon layer of animation timings to the seperate elements of the action. We can break this process down into primary, secondary and tertiary actions according to how they affect and are effected by the overall movement.
Primary Action are those actions that are central to any given moment. As an example, let’s consider a fairly straightfoward walk cycle. In such an animation, the action will be driven by leg and hip movement of a walking figure.
Once primary action is complete, the animator may go on to animate the Secondary Actions that assist the primary action. These movements are those that are usually linked to the primary actions and make for more efficient movements, such as the swinging arms and upper torso movement in a walk cycle. While such actions affects the overall movement they are not essential to its completion, that’s why it is consider as secondary actions.
After animator animated the secondary actions they will be able to move on to animate the next layer of detail to the sequence, Tertiary Action. These are actions that are simply the result of the primary and secondary actions, and are often the movement of those things that are simply attached to the main figure. These types of actions are often used for appendages or costume/character’s detail and are perhaps best shown by such things as the flapping ears of a running dog, the tail of galloping horse, a character’s hair or the ribbon on her dress. Such actions are usually of little consequence to the movement of the figure.