Glossary
Ease curves vary the timing of a superior function curve. A normal function curve charts an animated parameter value over time. An Ease curve charts changes to the time of a function curve over time.
The horizontal scale of an Ease curve represents normal time, just as it does for all function curves. The vertical scale of an Ease curve represents the time scale of the superior function curve the Ease curve is applied to. Changing the shape of an Ease curve changes the way time is interpreted by the affected function curve.
Imagine you have animated a bird flying around the sky. After viewing the animation you decide that you want to change the position of the bird so it moves quickly at the beginning of the animation and then slows to a leisurely pace towards the end.
You could accomplish this change by editing position keys, ranges, and function curves but it would require more work than using an Ease curve. Applying an Ease curve to the Position track provides a quick and easy solution.
Dragging the Ease curve causes time to compress near the beginning of the animation and stretch out near the end. You can tell that the bird's motion starts out fast and then slows down by looking at the effect the Ease curve has on the Position function curves.