Help for creating custom Spry transitions

I've mentioned one way to add more transitions to Spry in Upping Your Transition Count, but that assumes that you have pre-created easing equations. What if you none of the ones you've found meet your needs? Well you can create your own...if you know how to write one. All I've seen in my research is that your function needs to work like f(0) = 0 and f(1) = 1, but really what does that mean to someone that doesn't work with math functions much, and what is the 0 and 1 in this case when easing equations take 4 parameters (at least that's the case with Spry and Robert Penner's equations)?

To be honest, I really don't know (at least not yet), but I have found a tool that can be useful in creating a custom equation. Check out the easing function generator, a Flash application that allows you to use drag and drop or directly enter in some values to see what your easing equation will look like. For use with Spry, make sure to select the F5/FMX radio button at the top of the application. Drag and drop the numbered boxes at the bottom which will change the graph of the curve on the left. Then to see how the new equation changes the movement of an object, click on the red ball, then click elsewhere in the movie and the ball will move to that second location using your equation. Rinse lather, repeat as necessary to get an transition equation that you like.

Once you have an equation, copy the text of the function and paste it into SpryEffects.js at the end of the built in equations. Make sure to give the equation a unique name, and put a comma at the end of the previous equation. growSpecificTransition is the last transition in the default SpryEffects.js file (at least in 1.6.1), and the resulting code would look similar to:
growSpecificTransition: function(time, begin, change, duration)
{
if (time > duration) return change+begin;
var pos = time/duration;
return begin + (5 * Math.pow(pos, 3) - 6.4 * Math.pow(pos, 2) + 2 * pos) * change;
},

myNewTransition: function(t, b, c, d) {
var ts=(t/=d)*t;
var tc=ts*t;
return b+c*(17.495*tc*ts + -42.84*ts*ts + 35.695*tc + -11.2*ts + 1.85*t);
}


Once you add that to your copy of SpryEffects.js, then you can use your new transition like you would any other transition. For example, an accordion could be written as:
var Accordion1 = new Spry.Widget.Accordion("Accordion1", {transition: Spry.Effect.Transitions.myNewTransition});

Or because SpryEffects.js automatically adds all transition off of the Spry obejct, youc an use:
var Accordion1 = new Spry.Widget.Accordion("Accordion1", {transition: Spry.myNewTransition});

You can also try to integrate your new equation into the Spry Effects Transition Sample (online, or within the Spry download package: /samples/effects/transition_sample.html). Just add your equation to the SpryEffects.js for the sampler and add the name of your equation to the transitions select list, and you should be good to go.

Please post a link to any examples of any fun easing equations you've come up with. Also, if you happen to know how to write easing equations and can explain how in layman's terms, please do post your explanation, thanks!