W3C home > Mailing lists > Public > www-svg@w3.org > February 2013

Re: High Resolution Time

From: Dr. Olaf Hoffmann <Dr.O.Hoffmann@gmx.de>
Date: Sun, 10 Feb 2013 15:22:22 +0100
To: www-svg@w3.org
Message-Id: <201302101522.23215.Dr.O.Hoffmann@gmx.de>
Jonathan Chetwynd:

>you had not addressed my comment on 'scale' and your thoughts may be of 
>interest.

scaling/manipulation of 'time'? 
SMIL has a module for this and I think, there is a requirement to get
something like this for SVG2.
But what you can do with this is more to simplify some typical problems,
like doing the animation backwards or with another timing as noted.

But the recommendation you referenced is only about more precise 
time stamps, one already has for example in PHP - therefore nothing 
really new:
http://www.php.net/manual/en/function.microtime.php
Computers have this time information, but if they are connected
to a network with proper time information (NTP, GPS, wireless networks
for mobile phones etc), such time stamps are required to be corrected, 
because the local quarz oscillator of the device is not precise enough.
Usually such corrections are done with other programs than those 
trying to display some SVG or (X)HTML, therefore maybe not easy
to follow such a recommendation with a normal viewer with limited
access to the control or interpretation of the primary signal of the
local quarz oscillator.
As we can see with the CSS2.1 unit problem for lenghts, for several
implementors it was not even desirable to get proper information about 
the screen resolution, why should it work better for proper time
information? ;o)

>my feeling being that where one has a complex variety of timed events,
>it may be helpful to have a simple way to speed up - slow down the whole 
>animation,

This can be more difficult with declarative options, because attributes
of animation elements are currently not animatable themselves.
Obviously already today one can switch to another animation element
with different duration or keySplines with some event, but for example
my suggestion to have an option in SVG to conserve and to reuse
the current value of an animation effect was rejected, therefore it will
remain difficult to switch with a (user-)event in the middle of an 
animation to something different, but with the effect, that it looks like a
continuation.
With to-animation one has a simple access to a small subset of such
effects, but unfortunately the usual viewers have bugs and gaps for
to-animations, therefore in practice not really usable today due to
broken implementations.
With CSS-transitions one may have access to a similar subset,
once it becomes a recommendation, but they are only decorative 
and there are not really precisely defined events in CSS, only vague 
changes of states. 

Your use case to slow down or speed up depending on (user-)events
sound useful in specific situations, but if already simpler suggestions 
are rejected and to-animation implementations remain broken, there is 
not much hope for some advanced approaches for more declarative 
manipulations of animations.
Currently there is not even an option to pause an animation declaratively,
this would be one simple and apparent option to start with - already
helpful as an accessibility feature, especially if animations are used
together with elements like video, audio, animation (SVG tiny 1.2,
respecitively SMIL or 'HTML5'). 
But I think, there is an idea as well to use something like the SMIL
time containers in SVG2, this may help already in some situations to 
get more sequenced content with user interactivity.

Of course, one may have another decorative effect, if one is able to
manipulate animation elements with ecma-scripts, but because I do 
not use them and this option is not related to content, I have no 
experience with such an approach.

On the other hand, you cannot manipulate time in real life (well there are
funny situations in relativistic spacetime, but usually we live in a simpler
part of the universe).
And the options in computer games to restart at a specific time in the past, 
if you fail, feels always like cheating - therefore I think, the manipulation
of declarative animations is limited to use cases without the demand to
simuate something realistic ;o)
But for other uses cases - why not to think, how to do this?
Currently the solution may depend strongly on the specific problem one
wants to solve with this.


Olaf
Received on Sunday, 10 February 2013 14:22:53 GMT

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