- From: Brian Birtles <birtles@gmail.com>
- Date: Fri, 8 Apr 2011 10:13:55 +0900
- To: "Dr. Olaf Hoffmann" <Dr.O.Hoffmann@gmx.de>
- Cc: www-svg@w3.org
Dear Olaf, Thanks again for taking time to get back to me on this. I do appreciate your help. 2011/4/6 Dr. Olaf Hoffmann <Dr.O.Hoffmann@gmx.de>: >> The point of this change is not to add a variant but to remove one. > > Unfortunately this would remove possible applications as well, > therefore not a good idea from the authors point of view ;o) I believe neither the current behaviour nor the proposed behaviour can be easily produced by other means. (However, the current behaviour is more easily simulated since it requires calculating only one value. The proposed behaviour cannot be easily simulated.) I am still not aware of any use case for the current behaviour hence I propose adopting the more intuitive and consistent behaviour. > For to-animation, because it is neither additive or not-additive, one has > always to use the specific defined algorithm to get the intended > effect, therefore it works anyway different from values-animations, > including the frozen value. The complete effect is not additive, > why should the frozen value suddenly be additive, this is not > intuitive and does not fit to the model of the to-animation. Yes, to-animation is "is a kind of mix of additive and non-additive animation".[1] As SMIL 3.0 describes, "The underlying value is used as a starting point as with additive animation, however the ending value specified by the to attribute overrides the underlying value as though the animation was non-additive."[1] Using this description we could think of to-animation as becoming less additive as it progresses through the simple duration (since the starting point is additive and the end point is non-additive). If the animation is frozen part-way through the simple duration, the currently defined behaviour causes the to-animation to suddenly go from being partly additive to completely non-additive. The change I am proposing means there is no sudden change. A partly additive to-animation remains partly additive. That is why I claim this is more intuitive and more consistent with to-animation. > Well, I you have a look for example into the CSS transitions draft, > this might give an idea. > It is not perfect either, but indicates, that several people assume, > that something like this has use cases. Please provide specific reference. I can't see any case in CSS transitions where the transition is adding to a value in change, stops mid-interval, and then maintains that intermediate value masking underlying changes. > By the way, doesn't values like 'currentColor' and 'inherit' complicate > the model in a similar way? Those can behave similar to to-animations > (ok, the frozen part is excluded here) and some viewers do not > manage them correctly as well. These issues are confined to the animation model (including the automatic fallback to calcMode=discrete). The difficulty with the frozen to-animation is coupling between the two models. At any rate, it's too late to get this into SVG 1.1 now. It seems likely that implementations will simply have to deviate from the specification here. Thanks again for your help Olaf. Best regards, Brian [1] http://www.w3.org/TR/SMIL/smil-animation.html#animationNS-ToAnimation
Received on Friday, 8 April 2011 01:14:23 UTC