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Re: [1.2T-LC] Paced animation and complex types (ISSUE-2083)

From: Doug Schepers <schepers@w3.org>
Date: Wed, 01 Oct 2008 10:16:18 -0400
Message-ID: <48E38632.2060700@w3.org>
To: "Dr. Olaf Hoffmann" <Dr.O.Hoffmann@gmx.de>
CC: www-svg@w3.org

Hi, Dr. Olaf-

Thanks for your comment.  I've recorded this as ISSUE-2083 in our
Tracker, and when we resume telcons next week, after our Test Fest, we
will discuss this and get back to you soon.


Dr. Olaf Hoffmann wrote (on 10/1/08 9:32 AM):
> Hello SVG WG,
> 16.2.7 Paced animation and complex types 
> notes now for <list-of-points>, that 'There is no defined formula to pace a
> list of points. The request to pace should be ignored and the value of linear 
> used instead.'
> This is understandable and fine because
> 'Distance is defined for types which can be expressed as a list of values,
> where each value is a vector of scalars in an n-dimensional space. For
> example, an angle value is a list of one value in a 1-dimensional space 
> and a color is a list of 1 value in a 3-dimensional space.'
> and even more relevant:
> "paced
> Defines interpolation to produce an even pace of change across the animation. 
> This is only supported for values that define a linear numeric range, and for
> which some notion of "distance" between points can be calculated (e.g. 
> position, width, height, etc.)."
> And a list is not always a vector (a vector has an absolute value and a 
> direction) - <list-of-points> - no vector, no formula for a distance,
> therefore no paced animation defined in general. And there is no way 
> to get an interpolation with an even pace for such a list.
> 1. Surprisingly  there are (still) formulas given for <list-of-lengths>,
> <list-of-coordinates>, <list-of-numbers>, <path-data>.
> These lists are no vectors either, <path-data> is not even a list which can 
> be confused with a vector. Especially <list-of-points> is equivalent to a
> subset of <path-data> - and if the  equivalence of a subset of <path-data> 
> has no formula for a distance as identified already correctly, obviously the
> currently given formula for <path-data> results in nonsense and in
> general not into an interpolation with an even pace.
> The same applies for the other lists, because they do not represent vectors
> with one absolute value and one direction. Therefore there should be no
> formula too and authors should be discouraged to use calcMode paced with 
> such types, because if there are already some formulas implemented due to 
> SVG 1.1 or previous drafts, this will result in nonsense anyway.
> Note, that the related sample(s) in the test suite need to be fixed/removed
> too, for example animate-elem-53 (calcMode paced for points, <list-of-points>
> as already excluded in the current draft)
> 2. transform type scale is pretty fine now (according to the curent formula it
> is more one 2-dimensional value, not two 1-dimensional values) as translate 
> is and skewX/Y.
> rotate is more critical, but the new formula is already a big improvement
> compared to previous attempts. If the rotation center is not changed within
> the animation, this results indeed in a paced animation ;o)
> But it should be at least noted for authors, that it exists in general no
> paced animation, if the rotation center changes within the animation, 
> neither with the given formula nor with any other or whatever is already
> implemented in previous viewer versions or noted in SVG 1.1. 
> Note, that in the test suite animate-elem-82 describes still the (wrong)
> behaviour of SVG 1.1 for paced animateTransform and paced translate
> animateTransform is still insensitive to  implemented timing and 
> therefore useless (see long discussion from last year about this test
> including a provided alternative).
> Olaf
Received on Wednesday, 1 October 2008 14:16:50 UTC

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