From: "Nathan Shipley" <AE-List@media-motion.tv>
MIME-Version: 1.0
In-Reply-To: <list-6454098@media-motion.tv>
References: <list-6454098@media-motion.tv>
Date: Wed, 23 May 2018 11:00:01 -0700
Message-ID: <CAMtaTCz2o2UVYgBXZhBeks+8FB40kg-fjqfOuuwL6BT-GMBs_A@mail.gmail.com>
Subject: Re: [AE] Inverse Square Law for glows
To: After Effects Mail List <AE-List@media-motion.tv>
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This is really great, Brendan.  Well said and thanks for sharing.

On Tue, May 22, 2018 at 7:23 PM, Brendan Bolles <AE-List@media-motion.tv>
wrote:

> On Apr 19, 2018, at 10:41 PM, Chris Zwar wrote:
>
> > Sure it looks good but I don=E2=80=99t think it=E2=80=99s 100% mathemat=
ically perfect.
>
>
> I'm a little late to this thread, but...
>
> I don't think glow is inverse square, the apparent brightness of an objec=
t
> as it moves away from you in space is.  If glow were simply inverse squar=
e,
> you could simulate the falloff by applying Levels with gamma 0.5 to your
> 0.0-1.0 linear falloff.
>
> Actual glow in the real world is a function of how many bounces the light
> does in the lens/air before getting to the film/CCD through a non-direct
> path.  Depending on the circumstances, only a fraction of the light gets
> scattered in a certain direction, and then only a fraction of that is
> scattered back to the camera.  Sounds more like a logarithmic falloff tha=
n
> inverse square.
>
> Not having a logarithmic falloff plug-in, the multiple blurs thing works
> pretty well for me. In line with the logarithmic thing, I usually do some
> sort of expression for glow radius like:
>
> glowRadiusStart * Math.pow(glowStep, glowLayerIndex)
>
> This gets big quickly, but that's the idea!
>
> And of course, to physically simulate glow you'd want a linear float colo=
r
> space with Add mode for each layer and the glowing object to be way over
> 1.0.  Then because air/glass is pretty transparent I usually set the
> Transparency of each layer to 1% or so.
>
> Bonus points if you then bring the whole thing down a smidge (Levels
> output white 0.96 or something) because the glows added extra energy but
> the sum total of post-glow energy should be the same as the pre-glow.
>
>
> Brendan
>
>
> +---End of message---+
> To unsubscribe send any message to <ae-list-off@media-motion.tv>
>

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<div dir=3D"ltr">This is really great, Brendan.=C2=A0 Well said and thanks =
for sharing.</div><div class=3D"gmail_extra"><br><div class=3D"gmail_quote"=
>On Tue, May 22, 2018 at 7:23 PM, Brendan Bolles <span dir=3D"ltr">&lt;<a h=
ref=3D"mailto:AE-List@media-motion.tv" target=3D"_blank">AE-List@media-moti=
on.tv</a>&gt;</span> wrote:<br><blockquote class=3D"gmail_quote" style=3D"m=
argin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">On Apr 19, 20=
18, at 10:41 PM, Chris Zwar wrote:<br>
<br>
&gt; Sure it looks good but I don=E2=80=99t think it=E2=80=99s 100% mathema=
tically perfect.<br>
<br>
<br>
I&#39;m a little late to this thread, but...<br>
<br>
I don&#39;t think glow is inverse square, the apparent brightness of an obj=
ect as it moves away from you in space is.=C2=A0 If glow were simply invers=
e square, you could simulate the falloff by applying Levels with gamma 0.5 =
to your 0.0-1.0 linear falloff.<br>
<br>
Actual glow in the real world is a function of how many bounces the light d=
oes in the lens/air before getting to the film/CCD through a non-direct pat=
h.=C2=A0 Depending on the circumstances, only a fraction of the light gets =
scattered in a certain direction, and then only a fraction of that is scatt=
ered back to the camera.=C2=A0 Sounds more like a logarithmic falloff than =
inverse square.<br>
<br>
Not having a logarithmic falloff plug-in, the multiple blurs thing works pr=
etty well for me. In line with the logarithmic thing, I usually do some sor=
t of expression for glow radius like:<br>
<br>
glowRadiusStart * Math.pow(glowStep, glowLayerIndex)<br>
<br>
This gets big quickly, but that&#39;s the idea!<br>
<br>
And of course, to physically simulate glow you&#39;d want a linear float co=
lor space with Add mode for each layer and the glowing object to be way ove=
r 1.0.=C2=A0 Then because air/glass is pretty transparent I usually set the=
 Transparency of each layer to 1% or so.<br>
<br>
Bonus points if you then bring the whole thing down a smidge (Levels output=
 white 0.96 or something) because the glows added extra energy but the sum =
total of post-glow energy should be the same as the pre-glow.<br>
<br>
<br>
Brendan<br>
<br>
<br>
+---End of message---+<br>
To unsubscribe send any message to &lt;<a href=3D"mailto:ae-list-off@media-=
motion.tv">ae-list-off@media-motion.tv</a>&gt;<br>
</blockquote></div><br></div>

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