Good day to all,

I've just been teaching myself POVray in the last several days, and only 
just started working with media. I'm trying to get an effect where one 
light source is scattered and absorbed quite a bit by the media, but 
other light sources are not affected. The result (which I don't know if 
it's possible) would be that one of the objects in a scene has a bit of 
a halo, while everything else is perfectly visible. Unfortunately, even 
with "media_interaction off" in the other light sources, a high 
absorption will black out the entire scene.

Does anyone know how to get around this? Can it be gotten around?

-M.C. ArZeCh

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In article <3EB### [at] xithnet>, Eleven <pov### [at] xithnet> wrote:

> I've just been teaching myself POVray in the last several days, and only 
> just started working with media. I'm trying to get an effect where one 
> light source is scattered and absorbed quite a bit by the media, but 
> other light sources are not affected. The result (which I don't know if 
> it's possible) would be that one of the objects in a scene has a bit of 
> a halo, while everything else is perfectly visible. Unfortunately, even 
> with "media_interaction off" in the other light sources, a high 
> absorption will black out the entire scene.

Don't use absorbing media. Use scattering media with an extinction of 0. 
Actually, the way you're doing it is rather limiting and CPU intensive, 
just putting emitting media around the object would be better.

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: chr### [at] tagpovrayorg
http://tag.povray.org/

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Christopher James Huff wrote:
> Don't use absorbing media. Use scattering media with an extinction of 0. 
> Actually, the way you're doing it is rather limiting and CPU intensive, 
> just putting emitting media around the object would be better.

Alternately use scattering media and negative absorbing media.
e.g.
media{
   intervals 1
   confidence 0.0001
   variance 1
   ratio 0.5
   absorption   rgb<-0.5,-0.5,-0.5>
   scattering{1 rgb<0.5,0.5,0.5>}
}

-- 
Tim Cook
http://home.bellsouth.net/p/PWP-empyrean

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PGP-(--) t* 5++>+++++ X+ R* tv+ b++(+++) DI
D++(---) G(++) e*>++ h+ !r--- !y--
------END GEEK CODE BLOCK------

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Christopher James Huff wrote:

> Don't use absorbing media. Use scattering media with an extinction of 0. 
> Actually, the way you're doing it is rather limiting and CPU intensive, 
> just putting emitting media around the object would be better.

The only problem I find with that is that you don't get the effect of 
light pouring out of cracks in an object (which is really what I'm going 
for; guess I should have been more specific), though I suppose I could 
do something with manually adding emitting media in the proper shapes...

-M.C. ArZeCh

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In article <3EB### [at] xithnet>, Eleven <pov### [at] xithnet> wrote:

> The only problem I find with that is that you don't get the effect of 
> light pouring out of cracks in an object (which is really what I'm going 
> for; guess I should have been more specific), though I suppose I could 
> do something with manually adding emitting media in the proper shapes...

Ah, I thought you were just talking about a plain halo effect. To do 
this accurately you do need scattering, just set extinction to 0. If the 
beams of light don't need to correspond exactly to openings in the 
object, emitting media and a carefully designed density pattern might 
work.

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: chr### [at] tagpovrayorg
http://tag.povray.org/

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In article <3ebc4645@news.povray.org>, Tim Cook <z99### [at] bellsouthnet> 
wrote:

> Alternately use scattering media and negative absorbing media.

Why? It's more work, possibly slower...what possible reason is there for 
doing this?

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: chr### [at] tagpovrayorg
http://tag.povray.org/

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Christopher James Huff wrote:
> Why? It's more work, possibly slower...what possible reason is there for 
> doing this?

See my media wheel I posted a few ago in p.b.i ...negative absorption
and positive scattering give a scene that, if you don't have any
media-interacting lights, looks the same as (and afaict renders as
quickly as) the same scene without media, but you can turn on a media
interacting light and have it interact.

-- 
Tim Cook
http://home.bellsouth.net/p/PWP-empyrean

-----BEGIN GEEK CODE BLOCK-----
Version: 3.12
GFA dpu- s: a?-- C++(++++) U P? L E--- W++(+++)>$
N++ o? K- w(+) O? M-(--) V? PS+(+++) PE(--) Y(--)
PGP-(--) t* 5++>+++++ X+ R* tv+ b++(+++) DI
D++(---) G(++) e*>++ h+ !r--- !y--
------END GEEK CODE BLOCK------

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In article <3ebc71a5@news.povray.org>, Tim Cook <z99### [at] bellsouthnet> 
wrote:

> Christopher James Huff wrote:
> > Why? It's more work, possibly slower...what possible reason is there for 
> > doing this?
> 
> See my media wheel I posted a few ago in p.b.i ...negative absorption
> and positive scattering give a scene that, if you don't have any
> media-interacting lights, looks the same as (and afaict renders as
> quickly as) the same scene without media, but you can turn on a media
> interacting light and have it interact.

Have you actually tried setting extinction to 0?

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: chr### [at] tagpovrayorg
http://tag.povray.org/

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Christopher James Huff wrote:
> Have you actually tried setting extinction to 0?

Hmm nope, I'll play with that after my current render
finishes.

-- 
Tim Cook
http://home.bellsouth.net/p/PWP-empyrean

-----BEGIN GEEK CODE BLOCK-----
Version: 3.12
GFA dpu- s: a?-- C++(++++) U P? L E--- W++(+++)>$
N++ o? K- w(+) O? M-(--) V? PS+(+++) PE(--) Y(--)
PGP-(--) t* 5++>+++++ X+ R* tv+ b++(+++) DI
D++(---) G(++) e*>++ h+ !r--- !y--
------END GEEK CODE BLOCK------

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Christopher James Huff wrote:

> Ah, I thought you were just talking about a plain halo effect. To do 
> this accurately you do need scattering, just set extinction to 0. If the 
> beams of light don't need to correspond exactly to openings in the 
> object, emitting media and a carefully designed density pattern might 
> work.
> 

Cool, I got the light beams workin'. Thanks :) What exactly does 
"media_interaction off" do, then? Does it only apply to scattering effects?

And since it comes up, how exactly does one design a density pattern? 
The documentation doesn't seem very clear on it.

-M.C. ArZeCh

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