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25 Jul 2024 09:13:18 EDT (-0400)
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Subject: Re: MegaPOV glows in UberPOV
Date: 15 Nov 2016 15:57:17
Message: <789358013.500935726.443160.gdsHYPHENentropyAThotmaolDOTcom@news.povray.org>
clipka <ano### [at] anonymousorg> wrote:
>> It may be interesting at a later date to make them an actual volumetric
>> effect if they do not work that way currently.
> Define "volumetric effect".
> If you mean "an effect depending on properties of a 3D region of space,
> as opposed to properties of a surface", then glow already is a
> volumetric effect.
> If you mean "an effect computed by numeric integration along a ray, as
> opposed to symbolic integration", then no, glow does not match that
> definition. But I don't think it makes much sense to redesign the glow
> feature in such a manner: Like fog it is a lightweight feature, thanks
> to the use of symbolic integration, which comes at the cost of
> imperfections; changing it to use numeric integration could eliminate
> those imperfections, but would also turn it into heavyweight feature. If
> you want to realistically model halos caused by some scattering medium,
> use... (drumroll)... scattering media.

That makes complete sense in every way, and since I already implemented a
scattering media based glow, I can use those for ones close to the camera
and the normal ones otherwise.

I wasn't able to get the falloff of density and intensity to match real
glows quite correctly, because I do not know the function operating behind
it (and because of how media scales and/or my ignorance I had to use nested
shells), though if I did have the algorithm I could probably improve that
macro so we would have a "high quality" setting/macro available, which
might make a nice standard include.

I think I posted the source for it on the NG somewhere.


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