Join George Maestri for an in-depth discussion in this video Slow in and slow out, part of Animation Foundations: Fundamentals.
When animating objects we usually want to move them naturally. When there's a change in speed or direction it is because of a force acting on the object. This force will cause the object to accelerate and decelerate because of Newton's laws of motion. Consider an object that is stationary. When a force is applied to the object it accelerates. To put it more simply, the object goes from stationary to slow, to faster and faster still. In animation terms this is called a slow-in because the object goes into the motion slowly.
When objects decelerate they slow to a stop for the same reasons they accelerate. They're presented with an opposing force that slows the motion in the opposite direction, often to a stop. In animation terms this is known as a slow-out because the object comes out of its motion slowly. We've seen slow-in and slow-out before as animation curves. You can see that as the curve changes during the slow-in, the objects accelerate.
Constant speed is a straight line. Slow-out is a curve representing deceleration. Stop is a flat line. If we were to remove the slow-in and slow-out we would have a linear curve and the object would start and stop abruptly. Comparing the two you can see the difference. To sum up, adding a slow-in and slow-out to an animation can make it behave more realistically. This is because it makes the object appear as though it is being acted upon by external forces.
- Understanding forces and motion
- Working with center of mass
- Adjusting frame rates
- Understanding keys and keyframes
- Building animation paths
- Navigating the object hierarchy
- Staging an animation
- Animating to audio and music