Given that interpolation occurs when you want to move from value A to value B, there are infinite ways to cover the path from A to B. In fact, some visual effects are implemented through non-linear animations. A number of real-world experiences are tied to quadratic equations – think about gravity or acceleration in general. Another huge set of cases are based on trigonometric functions such as sine and cosine – think about oscillations or springs.
A simple way to apply a modifier function to our interpolation is to transform its argument – time. We've already introduced the concept of normalized time over a duration period – N(t) – ranging from 0 to 1.
Now, think about what would happen if, instead of using a linearized interpolation of time, you substituted it with a non-linear one. The values of the interpolation will vary accordingly, without changing the interpolation...