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References: <list-5002658@media-motion.tv>
From: Bruce Wainer <brwainer@gmail.com>
Date: Wed, 13 Mar 2013 22:00:05 -0400
Message-ID: <CAPEXuiy2erieLmce-nETNN=g_G79GYR71JxwBy1ekMiYB3cn+w@mail.gmail.com>
Subject: Re: [AE] Divide by Zero Errors...
To: After Effects Mail List <AE-List@media-motion.tv>
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Andrew,

The only thing I can think of is that the Math.exp() method is returning 0
or infinity when a large number is passed in. So if e^(decay*t) is too
large of a number, the result becomes 0 or infinity (not sure which it
would be but either way division would be impossible). With exponents this
is really easy to do, as the numbers get very large very quickly.

Just to test, if you replace the "Math.exp(decay*t)" with something else,
do the errors go away? If so you've found the problem code. I think it has
to be though because it's the only divisor that is variable. The only
solution would be to protect that code by creating a variable to hold that
result. If it is 0 or infinity, reassign that variable to a very very large
number (preferably the maximum value that the datatype can hold).

Sorry for using general programming terms, I've done much more Java, PHP,
and SQL lately than Javascript (which the After Effects expression engine
is based on). Oh the joys of being a Media Arts and Telecommunications dual
major.

Bruce Wainer


On Wed, Mar 13, 2013 at 8:55 PM, Andrew Embury <aembury@gmail.com> wrote:

> Hey guys/ gals!
>
> Quick question....
>
> Whilst animating in AE tonight I was using the following expression:
>
> amp = .03;
> freq = 4.0;
> decay = 12.0;
> n = 0;
> if (numKeys > 0){
> n = nearestKey(time).index;
> if (key(n).time > time){
> n--;
> }}
> if (n == 0){ t = 0;
> }else{
> t = time - key(n).time;
> }
> if (n > 0){
> v = velocityAtTime(key(n).time - thisComp.frameDuration/10);
> value + v*amp*Math.sin(freq*t*2*Math.PI)/Math.exp(decay*t);
> }else{value}
>
>
> Never ever have I since have encountered so many "Divide by Zero" errors
> in my life with AE.
>
> Currently working with CS6 and I am applying this expression to Scale,
> Position, and Rotation.
>
> Any help would be greatly appreciated.
>
> Thank you.
>
> - Andrew
>

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<div dir=3D"ltr"><div>Andrew,<br><br>The only thing I can think of is that =
the Math.exp() method is returning 0 or infinity when a large number is pas=
sed in. So if e^(decay*t) is too large of a number, the result becomes 0 or=
 infinity (not sure which it would be but either way division would be impo=
ssible). With exponents this is really easy to do, as the numbers get very =
large very quickly.<br>

<br>Just to test, if you replace the &quot;Math.exp(decay*t)&quot; with som=
ething else, do the errors go away? If so you&#39;ve found the problem code=
. I think it has to be though because it&#39;s the only divisor that is var=
iable. The only solution would be to protect that code by creating a variab=
le to hold that result. If it is 0 or infinity, reassign that variable to a=
 very very large number (preferably the maximum value that the datatype can=
 hold).<br>

<br></div>Sorry for using general programming terms, I&#39;ve done much mor=
e Java, PHP, and SQL lately than Javascript (which the After Effects expres=
sion engine is based on). Oh the joys of being a Media Arts and Telecommuni=
cations dual major.<br>

<div><div><br></div><div>Bruce Wainer<br></div></div></div><div class=3D"gm=
ail_extra"><br><br><div class=3D"gmail_quote">On Wed, Mar 13, 2013 at 8:55 =
PM, Andrew Embury <span dir=3D"ltr">&lt;<a href=3D"mailto:aembury@gmail.com=
" target=3D"_blank">aembury@gmail.com</a>&gt;</span> wrote:<br>

<blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1p=
x #ccc solid;padding-left:1ex"><div dir=3D"ltr">Hey guys/ gals!<div><br></d=
iv><div>Quick question....</div><div><br></div><div>Whilst animating in AE =
tonight I was using the following expression:</div>

<div><br></div><div><div>
amp =3D .03;</div><div>freq =3D 4.0;</div><div>decay =3D 12.0;</div><div>n =
=3D 0;</div><div>if (numKeys &gt; 0){</div><div>n =3D nearestKey(time).inde=
x;</div><div>if (key(n).time &gt; time){</div><div>n--;</div><div>}}</div><=
div>if (n =3D=3D 0){ t =3D 0;</div>


<div>}else{</div><div>t =3D time - key(n).time;</div><div>}</div><div>if (n=
 &gt; 0){</div><div>v =3D velocityAtTime(key(n).time - thisComp.frameDurati=
on/10);</div><div>value + v*amp*Math.sin(freq*t*2*Math.PI)/Math.exp(decay*t=
);</div>


<div>}else{value}</div><div><br></div><div><br></div><div>Never ever have I=
 since have encountered so many &quot;Divide by Zero&quot; errors in my lif=
e with AE.</div><div><br></div><div>Currently working with CS6 and I am app=
lying this expression to Scale, Position, and Rotation.</div>


<div><br></div><div>Any help would be greatly appreciated.</div><div><br></=
div><div>Thank you.</div><span class=3D"HOEnZb"><font color=3D"#888888"><di=
v><br></div><div>- Andrew</div></font></span></div></div>
</blockquote></div><br></div>

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