- From: Dean Trower <dean@omnivisiontechnology.com>
- Date: Wed, 26 Jun 2013 11:04:28 +1000
- To: <public-fx@w3.org>
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) Having keyword shortcuts for these curves (perhaps "parabolic-rise" and "parabolic-fall"?) 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). Thanks for your consideration, Dean Trower
Received on Wednesday, 26 June 2013 01:04:48 UTC