# [SMIL30 LC comment] 12. SMIL 3.0 Time Manipulations

From: Dr. Olaf Hoffmann <Dr.O.Hoffmann@gmx.de>
Date: Sun, 12 Aug 2007 13:01:42 +0200

Message-Id: <200708121301.42551.Dr.O.Hoffmann@gmx.de>
```
Hello SMIL working group,

12.3.1

typo:

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

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

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.

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

Example:

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

-> speed="2.0" ?

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

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