Slow In & Slow Out

Definition

‘Slow In’ and ‘Slow Out’ – terms in animation that are used to describe an important principle: an object or a character in animated video start their movements out more slowly, then picks up speed and finishes with deceleration. The beginning and end of the movement are softened. 

Acceleration and Deceleration in Movements

All types of movements start with acceleration and end with deceleration. The same goes for almost everything in real life – when you are up to throw a ball, start running, jumping, and so on. Imagine that a character gets a car in and immediately “flies” at a speed of 100 kilometers per hour. Then he or she arrives at the right place and at the same moment the speed drops sharply to zero – a complete stop. This action is missing some stages – a car should accelerate to 100 km/h, and it slows down in the right place.

Such animation looks more realistic, as it is the principle of our physical world as well. Therefore, the animator should draw the movements in such a way that most of the frames are near the key poses: a character or an object seems to slide from one arrangement to another, slowly leaving the pose and slowing down in the other.

Where else are “Slow In” and “Slow Out” used

The terms “Slow In” and “Slow Out” are part of the 12 principles of animation. Acceleration and deceleration of movements are widely used in any type of animation. For example, in video games animation.