Anticipation is where you set up the audience for something that is about to happen.
For example: If you have a character that leaps in the air, don't have them go from a neutral standing position to immediately airborne. They need to gain energy. Usually to anticipate something, your character will need to move opposite the direction they're about to go. Notice the character underneath needs to go down in order to anticipate jumping up.
Ever seen an animation where all the movements are quick and snappy, but somehow still appear smooth and satisfying?
That’s likely because the animators used anticipation to set up each movement. When you give the audience a moment to anticipate what’s coming, even rapid actions won’t feel jarring. Anticipation is a crucial animation technique that lets you create lively, dynamic animations that flow well, no matter the speed.
Below, look at the drawings on the left. If you inbetweened from one to the other you'd have a smooth but rather subtle animation. Perhaps if the character is mildly surprised and they're taking time to process, this could work. However for a fast animation, going straight inbetween might feel a little jarring.
Now look at the drawings to the right. If you want to create a snappier animation, it becomes helpful to build anticipation. The two red frames inbetween would go in the opposite direction, and they would happen rather quickly. Then when you snap to the landing spot, since we anticipated the movement, the audience should understand.
Below, is the same concept broken down a little futher.
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This video serves as a nice recap of this topic.
Anticipation signals the beginning of a new movement. Simlarly, overshoots, work at the end of a movement to help properly emphasize the ending of. amovemet. An overshoot is when an object moves past it's landing keyframe. It can be used to make a movement feel more powerful or carry more weight.