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Re: ISSUE-2083 (Paced-anim-complex): Paced animation and complex types [Last Call: SVG 1.2 Tiny ]

From: Anthony Grasso <anthony.grasso@cisra.canon.com.au>
Date: Mon, 20 Oct 2008 03:32:12 +1100
Message-ID: <48FB610C.8040109@cisra.canon.com.au>
To: Dr.O.Hoffmann@gmx.de
CC: SVG Working Group WG <public-svg-wg@w3.org>

Hi Dr. Hoffmann,

The SVG Working Group discussed this issue and I was given ACTION-2317 to make 
changes to the specification to address this issue.

The following changes have been made to the animation chapter to address this issue.
  - The formulas for lists and paths in Section 16.2.7 [1] were removed and were 
noted to be unspecified.
  - A noted was added in Section 16.2.9 "calcMode" [2] to discourage authors 
from using calcMode paced for constructions other than scalars and colors.
  - A noted was added in Section 16.2.9 "keyTimes" [3] to encourage authors to 
calculate keyTimes for when calcMode is linear for the critical unspecified cases.

These changes will appear in the next publication of the specification.

Please let us know at your earliest convenience if the changes to the 
specification are satisfactory.

Kind Regards,

Anthony Grasso.

[1] http://dev.w3.org/SVG/profiles/1.2T/master/animate#complexDistances
[2] http://dev.w3.org/SVG/profiles/1.2T/master/animate#CalcModeAttribute
[3] http://dev.w3.org/SVG/profiles/1.2T/master/animate#KeyTimesAttribute

SVG Working Group Issue Tracker wrote:
> ISSUE-2083 (Paced-anim-complex): Paced animation and complex types [Last Call: SVG 1.2 Tiny ]
> http://www.w3.org/Graphics/SVG/WG/track/issues/2083
> Raised by: Doug Schepers
> On product: Last Call: SVG 1.2 Tiny 
> Dr. Olaf Hoffmann
> <http://lists.w3.org/Archives/Public/www-svg/2008Oct/0004.html>:
> [[
> 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).
> ]]
Received on Sunday, 19 October 2008 16:32:57 UTC

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