Easing function: Ease-out-in (opposite of Ease-In-Out) I'm seeking an easing function that is the twin of the popular Ease-In-Out easing function-- ![enter image description here]( **Desired Behaviour** Begins quickly, slows down in middle, ends quickly. **References** Keep your eye on the black portion of the screen in this _Sonic Heroes_ Stage Intro animation. Notice how the black screen gives way quickly at first, slows down when the screen is half-revealed, then quickly disappears. < Here's a quick reference of what the graph should look like ![enter image description here]( My attempts at curve fitting and experimentation haven't given me the equation / function I need, unfortunately. Any help would be appreciated!

How about this:

$y(x) = (x^3-2x^2+x)m_0+(-2x^3+3x^2)+(x^3-x^2)m_1$

where $m_0$ and $m_1$ are two positive constants.

Bigger $m_0$ and $m_1$ will result in more wavy curve. Here are two examples:


Example 1: $m_0=m_1=3$
![enter image description here](

Example 2: $m_0=m_1=4$
![enter image description here](