Follow Through and Overlapping Action

Follow through is the movement that happens after the actual action. This makes sense when you think about the conservation of momentum. If you throw a ball your hand would gain speed, since your hand has mass it wants to keep going (Newton's First law). This is the follow through time.

Follow through also helps to define the mass of something if it is light it can slow down very quickly. But if it is something large it will move slowly and slow down slowly. If two objects are moving at the same speed the larger one will travel farther unless more force is applied to slow it down.

If there is a large dinosaur in an animation it is going to make slower changes in movement; where as if there is a small bird it can hop from point A to B to C in a blink of an eye. The follow through action can almost be disregarded with some thing small such as a bird and no one would comment about it. If you ignore the follow through on something large, people will notice. They may not know why, but they will say that it just didn't move right.

Overlapping Action is something else used to make things look real. Overlaping Action is the starting of a new action before the previous one was finished.

Walt Disney explained it best in this quote:
"It's is not necessary for an animator to take a character to one point, complete that action completely, and then turn to the following action as if he had never given it a thought until after completing the first action. When a character knows what he is going to do he doesn't have to stop before each individual action and think to do it. He has it planed in advance in his mind."