[SMIL30 LC comment] 12. SMIL 3.0 Time Manipulations

Hello SMIL working group,

some comments on chapter 12:

12.3.1

typo:

'... as well as any time maniuplations defined ...'
->
'... as well as any time manipulations defined ...'

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12.3.2

'It will produce a simple pendulum swing on the target 
(assume that the target is a pendulum shape with the transform 
origin at the top):
<animateTransform type="rotate" from="20" to="-20" dur="1s" 
repeatCount="indefinite"
        accelerate=".5" decelerate=".5" autoReverse="true" ... />

The pendulum swings through an arc in one second, and then back again 
in a second.
....
This produces a realistic looking animation of real-world pendulum motion.'

-> Note that the motion of a (rotating, mathematical) pendulum is an
    anharmonic oscillation. It is technically not easy to build a pendulum
    with such a motion, therefore real-world pendulums behave different.
-> The motion related to these attributes is that of a constant force 
    (free fall close to the earth surface) as far as I understand this. With
    this example it should be possible to produce a quadratic spline
    approximation for a harmonic oscillation, because it includes
    autoReverse="true", however I did not check, if the given example
    really is the correct quadratic spline approximation for a sine related 
    to a harmomic oscillation and it is not the motion of a pendulum,
    especially not for large amplitudes.
-> For (an)harmonic oscillations the autoReverse is still very useful, but the
    approximation of the motion requires itself a values-animation with
    calcMode spline and maybe keyTimes. Additionally the values list needs to
    be calculated symmetrically around '0' to make use of the autoReverse.


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Example:

"<par speed=2.0>
   <animate begin="2s" dur="9s" speed="0.75" .../>
</par>"

-> speed="2.0" ?

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12.3.3

wording?

'r(t) is the speed modification due to acceleration and deceleration, 
at any time t within the simple duration.'

-> as far as I understand this, r(t) is the run rate itself at any time t,
not its modification, this would be dr/dt and would be called acceleration.

better:
->
'r(t) is the run rate, time dependent due to acceleration and deceleration, 
at any time t within the simple duration.'

Received on Sunday, 12 August 2007 11:15:54 UTC