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[SMIL30 LC comment] 3.4 and 3.6

From: Dr. Olaf Hoffmann <Dr.O.Hoffmann@gmx.de>
Date: Fri, 17 Aug 2007 17:35:07 +0200
To: www-smil@w3.org
Message-Id: <200708171735.07637.Dr.O.Hoffmann@gmx.de>

Hello SMIL working group,


some comments related to the chapters
3.4 and 3.6:


3.4.1 The simple animation function f(t)


'The animation function is a function of the current position, as well 
as of time:
f(t,u) = (u*(2.5s-t)/2.5s) + 10*(t/2.5s)'

-> u is undefined at this text position.
Better:
'The animation function f is a function of the current position u(t), 
as well as of time
t (here given in seconds):
f(t,u(t)) = (u(t)*(2.5s-t)/2.5s) + 10*(t/2.5s)'

Alternatively it would be useful too to define often used symbols at the 
top of the animation chapter.
This is done in 3.4.2, but this is too late for this section, this indicates
a bad document structure...

------------------

'The simple animation function defined by an animation element is a 
function of time, 
f(t), defined for times t, 0<=t<=d, where d is the simple duration of the 
element.'

-> define or reference definition of 'simple duration'

------------------

'The animation effect function, F(t,u), of an animation element with 
active duration AD ...'

-> define or reference definition of 'active duration'

--------------------


'3.4.2 Summary of symbols used in the semantic descriptions

This section is informative.'

-> The symbols are used in normative parts, how can this be informative?
How can the normative parts be understandable with only informative defined
symbols? ;o)

-> reference definitions of  'simple duration', 'active duration' ...

-------------------
'3.4.3 The animation sandwich model

This section is informative.'

This was not indicated as informative in SMIL2 - sure, that this is 
informative?
It contains  (!)important (?) information about priorities of animations.
And if it is informative, what about this in a normative part of 3.4.1:
'This is detailed in The animation sandwich model.'
If the section is only informative and not normative, it cannot contain
any information relevant for a normative part?

--------------------

'Specifically, animating an attribute defined in XML will modify the 
presentation 
value before it is passed through the style sheet cascade, using the XML DOM 
value as its base. Animating an attribute defined in a style sheet language
will modify the presentation value passed through the remainder of the
cascade.'

-> For example the style sheet language CSS has properties and no
attributes, what about them? 
Does XSL have attributes (I think, it has mainly formatting objects and
properties)? Which style sheet language defines attributes?
Better:
'Animating an attribute or property defined in a style sheet language will 
modify the 
presentation value passed through the remainder of the cascade.'?
or if there are no attributes in style sheet languages:
Animating a property defined in a style sheet language will modify the 
presentation value passed through the remainder of the cascade.'?

-> If we take as an example a basic shape from SVG, for them presentational 
XML attributes and CSS properties exist with the same meaning and the
same name, for example the property/attribute fill. If we use
attributeType XML and CSS we can distinguish between them.
This paragraph means that the animation using attributeType XML is
applied before it is passed through the style sheet cascade, while
with attributeType CSS (or auto) it is applied to the remainder of the
cascacde. Is this correct? This means animations using attributeType XML
are overwritten for example by external author style sheets, because 
those are later in the style sheet cascade. But using attributeType CSS
means, the animation superseedes the style sheets again (if there is no
!important from a user style sheet). Is this correct?
 
------------------------------
3.4.5 The animation effect function F(t,u)


typo?

'The effect of the animation is to to just use the value for f(0), setting 
the fill color to red for the remainder of the animate element's duration.'
->
'The effect of the animation is just to use the value for f(0), setting the
fill color to red for the remainder of the animate element's duration.'?


---------------------

'For example, the path notation for a simple arc (detailed in 
The animateMotion element) 
can be used to describe a bouncing motion:

<img ...>
   <animateMotion path="m 0 0 c 30 50 70 50 100 0 z" dur="5s"
      accumulate="sum" repeatCount="4" />
</img>'

-> Note that this example is in the BasicAnimation module and references
animateMotion from the BasicAnimation module but the path attribute is 
from the SplineAnimation module. This might confuse a little bit and
is not very comfortable for readers, if they really want to understand
this. 
-> minimal improvement would be a reference from the 'path notation' to
the related section of the SplineAnimation module and a note, that for
this example the SplineAnimation module is required...




--------------------
3.4.6 Additive animation

'An element may be defined as additive only if addition is 
 defined for the type of the target attribute.'

-> What happens, if this is not explicitely specified for the 
target attribute? No animation at all?

-------------------

'  This section is informative.

When there are multiple animations defined for a given attribute that overlap 
at any moment, the two either add together or one overrides the other...'

-> Sure that this is only informative? In SMIL2 it was not indicated as 
informative 
and contains important (?) information on priorities and about the question, 
for 
which types of attributes additive animation may be defined...   

 -------------------

'<img top="10" ... >
  <animate dur="10s" repeatDur="indefinite"

           attributename="top" from="20" by="10"

           additive="sum" accumulate="sum" />
</img>

The animation adds to the original value of 10 that was set for "top", 
and begins at the value 30. It moves down by 10 pixels to 40, then repeats. 
It is cumulative, so the second iteration starts at 60 (the value of 40 from
the previous iteration plus 20) and moves down by another 10 to 70, and 
so on.'

-> better:
'... (the value of 30 from the previous iteration plus 20 from the from
attribute and plus 10 from the underlying value) ...'

This is not important in this situation, but for attributes with not
commutable addition the order of the additions is important 
(for example SVG has such attributes), therefore it is important to 
pronounce that 60 results from three additions with numbers from 
three different sources...



------------------------

3.6.2 Specifying the simple animation function f(t)


- What is recommended for calcMode paced, if there is
a known procedure to produce an even pace of change 
across the animation, but this procedure does not interpolate
between the values? This happens for example for a list
of numbers or coordinates as animated values.
Such lists are no vectors, sometimes lists of vectors.
Fallback to linear? 
A SMIL3 example is the new viewBox, as already commented.
Received on Friday, 17 August 2007 15:42:47 UTC

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