Anticipation, Follow Through, Overlapping Action, and Secondary Action

The bookends and flourishes of a primary action.

When I first read the explanation of follow through and overlapping action in the Illusion of Life, I thought “This is about as confusing as it gets!” Johnston and Thomas’ description makes these two principles out to be awkward dance partners, stepping on each other’s cartoonish feet. I re-read carefully and went looking for other explanations online, most of which parroted the Illusion of Life. Then I decided to come up with my own explanation.

First, every action is a complex choreography of a primary action (a jump, a bow, a twirl, a trip) and one or more smaller actions connected to the primary action. These smaller actions are the things that make the primary action believable and interesting.

Every primary action has a moment of preparation and a moment of recovery. These smaller actions that bookend the primary action are anticipation and follow through.

Let’s illustrate: stop reading and jump up as high as you can, trying to touch the ceiling or the sky. (This is a fun and only slightly dangerous activity to do in the classroom). If we consider the movement of the body through the air as the primary action, then the crouching movement we make before we start moving upwards is the anticipation of the jump. Try jumping without crouching down first — it doesn’t work very well. Every action has a pre-action that most often moves in the opposite direction of the main action. Think about pulling your leg back before a kick or tilting your head back before a sneeze.

Every primary action has a moment of preparation and a moment of recovery: anticipation -> action -> follow through.

When you land from your jump, you will automatically bend your knees to cushion your body hitting the ground, once again going into a slight crouch. This crouch that follows the primary action is the follow through. You could think of it as the anti-anticipation. Can you land a jump without any sort of cushion or bend in your knees? (Ouch!) We need that moment of recovery to slow the momentum of the primary action and come gradually to a stop. Often times, we have to overshoot our final resting spot to account for this momentum and then settle into our final resting spot (overshoot is another, more specific animation term associated with follow through). In more complex actions, the follow through of one movement may blend into the anticipation of the next movement. For example, in a walk cycle the low point key frame is both the follow through of the previous step and the anticipation of the next step.

Where then, does overlapping action dance if not partnered with follow through (as suggested in The Illusion of Life)? Overlapping action also is connected to the primary action. It’s realm is all the things that flop, flow, flap and follow behind the central mass of the subject. Tails, capes, hair, jewelry, sometimes even heads and arms. Overlapping action follows the same line of action as the primary mass, but it does so a few frames behind the primary mass. Overlapping action often involves breaking a curve or joint, i.e. going from C curve to an S curve back to a C curve.

You might have a good deal of overlapping action in your follow through stage, which is why they are often confused or at least grouped together. However, overlapping action will also appear in your anticipation phase. And in your primary action phase. So, it is not just related to follow through.

Secondary Action is our final lonely dancer. But it too is connected to primary action. Secondary action is something that is under the character’s control that embellishes or enhances the primary action in a way that adds character or personality. The difference between the embellishments of overlapping action and secondary action is that secondary actions are voluntary on the part of the character, while overlapping action is (mostly) involuntary. We can’t control how our hair flows in the wind or our cape trails behind us as we jump, but we can control the little flick of our head and the wiggle of our fingers that show how delighted we are feeling. This little flick of the head and finger wiggle are secondary actions to the primary action of jumping, while the cape and hair are overlapping actions. Secondary actions are voluntary, driven by the character; overlapping actions are driven by momentum and physics, thus involuntary.

Okay, yes, once we start layering these things together they do all start to tread on each other’s toes and roll into some great animation. Developing a precise vocabulary is important for analysis and description, especially when trying to figure out what exactly is going wrong with an animation (“I think you need more follow through on that action…” “The breaking of the curve on the overlapping action is not quite right…” “Maybe add some secondary action to give a stronger sense of the character’s mood…”)

At some point we can then step back and enjoy the complex intertwining of all these principles around a single action. Anyone up for a dance party?