- From: Brian Birtles <bbirtles@mozilla.com>
- Date: Wed, 26 Jun 2013 06:32:01 -0700 (PDT)
- To: Dean Trower <dean@omnivisiontechnology.com>
- Cc: public-fx@w3.org
Hi Dean, Thanks very much for your feedback. I think this is something we can do. Currently we have a lot of ideas for timing functions--we definitely want to be able to do bounce and spring effects in the future. The current thinking is to put this in a separate spec since we discovered there are lots of different possibilities (some animation APIs have about 40 different predefined curves!) and some of the easy-looking ones are hard to parameterise in a way that's author-friendly. But as for the two curves you suggested, since they are simple keyword mappings onto single-segment cubic Bezier curves it's probably within scope of this spec. I will be travelling for the next few days so, to make sure we don't lose track of this feedback, would you mind filing a bug for this?[1] If not, I'll do it when I get a chance. Thanks again! Best regards, Brian [1] https://www.w3.org/Bugs/Public/enter_bug.cgi?product=FXTF&component=Web%20Animations ----- Original Message ----- From: "Dean Trower" <dean@omnivisiontechnology.com> To: public-fx@w3.org Sent: Wednesday, 26 June, 2013 10:04:28 AM Subject: [web-animations] Suggestion - parabolic cubic-bezier timing function keywords 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 13:32:29 UTC