ActionScript 2.0 :: Easing Equations For Dynamic Tweening?

Virtually the only dynamic ease-tweening you ever see in Actionscript is the ubiquitous "exponential ease-out." You know, the Zeno's paradox, go halfway every time, Barney's menu method:

distance = finalX - _x;
_x += distance / 2;

It's wonderfully simple and easy to code, but it lacks flexibility. You can choose your destination, but you can't specify, "I want to get there in 40 frames." Also, easing *in* with the same method is not so easy. There are many mathematical approaches to calculating an eased tween. I've derived some easing equations using three different curves: quadratic, sinusoidal, and exponential (as well as a trivial linear equation). Each of the three curves has its own particular "style" of easing; it's quite fun to compare their aesthetics.

All of the equations allow you to specify the beginning value, the change in the value, the duration of the tween, and the current time. Note that the equations will work for both frame-based and time-based animation. That is, duration and current time can be either frames or seconds/milliseconds.Here are the quadratic easing equations. I'll post the other two sets soon.

Code:

// simple linear tweening - no acceleration
// t: current time, b: beginning value, c: change in value, d: duration
Math.linearTween = function (t, b, c, d) {

[code]....

Right now, the equations are all set at "maximum easing", analogous to an easing setting of 100% in Flash's Frame panel. It is fairly simple to adapt the equations so you can specify an easing percentage. Personally, I almost always use 100% manual easing within Flash.

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