Is it possible to specify a custom timing functions for CSS transitions?

I use CSS transitions pretty frequently now but find it limiting to开发者_JS百科 only have access to ease-in, ease-out etc. The bezier-curve option appears to allow the most control but even this does not allow you to specify an actual easing equation that would simulate elastic easing etc.. Is there another option or does one need to resort to javascript to perform this type of animation?

You can use Caesar to generate CSS for different equations.

I found there is no way to do an elastic transition with pure CSS. However you can cheat and do a CSS animation. This is what apple uses on their site:

@-webkit-keyframes open-1 {
    from { opacity:0; -webkit-transform:translate3d( 210px, -145px, 0); }
    25%  { opacity:1; -webkit-transform:translate3d( -15.6px, 4.1px, 0); }
    30%  { opacity:1; -webkit-transform:translate3d( -10.3px, 2.7px, 0); }
    35%  { opacity:1; -webkit-transform:translate3d( 0, 0, 0); }
    40%  { opacity:1; -webkit-transform:translate3d( 4.5px, -1.2px, 0); }
    45%  { opacity:1; -webkit-transform:translate3d( 2.9px, -0.8px, 0); }
    50%  { opacity:1; -webkit-transform:translate3d( 0, 0, 0); }
    55%  { opacity:1; -webkit-transform:translate3d( -1.3px, 0.3px, 0); }
    60%  { opacity:1; -webkit-transform:translate3d( -0.8px, 0.2px, 0); }
    65%  { opacity:1; -webkit-transform:translate3d( 0, 0, 0); }
    70%  { opacity:1; -webkit-transform:translate3d( 0.4px, -0.1px, 0); }
    75%  { opacity:1; -webkit-transform:translate3d( 0.2px, -0.1px, 0); }
    80%  { opacity:1; -webkit-transform:translate3d( 0, 0, 0); }
    85%  { opacity:1; -webkit-transform:translate3d( -0.1px, 0, 0); }
    90%  { opacity:1; -webkit-transform:translate3d( -0.1px, 0, 0); }
    to   { opacity:1; -webkit-transform:translate3d( 0, 0, 0); }
}

These animations are used to great extent on Apple's own website: http://www.apple.com/mac/

Obviously this is powerful to some extent -- since the animations are percentages you can easily change he duration and retain the effect.

However, this is still very static. Let's say you want to click a button and have it perform an elastic scaling animation. No problem, one animation can be used over and over again for each button. But let's say you want to have an element elastically snap it's position to wherever the user most recently clicked or tapped on the screen. Well in this case you'd need to dynamically recalculate the keyframes and then apply the animation to the element.

At the time of this writing I don't know that there are any good examples of dynamically generating CSS animations on the fly inside of javascript. In fact it probably warrants another question. All in all this is the only pure CSS way I found to do render a complex easing equation such as elastic easing purely with CSS.

Actually you don't need a JavaScript library to support complex easing functions like bounce-ease-in or elastic-ease-out. Here's the CSS3 Animation Generator tool which generates the keyframes for you, and enables 12 additional easing functions not supported by the w3c spec:

http://www.css3animationgenerator.com/

i know that if you're using mootools you could write your own equation:

http://mootools.net/docs/core/Fx/Fx.Transitions

Class: Fx.Transition

This class is only useful for math geniuses who want to write their own easing equations. Returns an Fx transition function with 'easeIn', 'easeOut', and 'easeInOut' methods.

Maybe the other libraries like jquery or prototype have the same class, probably they do have something similar.

Good Luck!