22483 2013-06-26 17:53:26 +0000 Request for keywords representing parabolic cubic-bezier timing functions 2013-06-26 17:53:26 +0000 1 1 1 Unclassified FXTF Web Animations unspecified All All NEW P2 enhancement --- 1 f266704 web-anim-bugs oldest_to_newest 89909 0 f266704 2013-06-26 17:53:26 +0000 At the moment, the Web Animations draft defines only the keywords "linear", "ease", "ease-in", "ease-out" and "ease-in-out" as shortcuts to cubic-bezier(...) timing functions of certain shapes. I'd like to suggest that a couple more such keywords be added to this list - specifically, for *parabolic* timing functions: Representing the path objects take either rising, or falling, under gravity. The reason is that making objects appear to rise, fall, or bounce under gravity is I'd expect a fairly common use-case for CSS animation --- but using any of the ease-* curves to do it will result in wrong-looking (unphysical) behaviour: Such animations require parabolic timing functions to look correct. Rising and falling half-parabolas (somewhat similar in shape to ease-out and ease-in respectively) are also representable using cubic bezier curves, specifically (assuming my math is correct): rise: cubic-bezier(0.33333, 0.66667, 0.66667, 1) fall: cubic-bezier(0.33333, 0, 0.66667, 0.33333) (Note that exact values are really 1/3 for 0.33333 and 2/3 for 0.66667 respectively) Having keyword shortcuts for these curves (perhaps "parabolic-rise"/"parabolic-fall", or perhaps "accel"/"decel"?) will facilitate the easy creation of physically-correct rise/fall/bounce animations, and will also make it clear at a glance, from looking at the CSS, just what such animations are supposed to do. (Which certainly isn't the case if you use cubic-bezier(...) with numerical arguments instead).