But it has not been a long time. 

	A nutshell. I have copied scattering media parameters from
scenes where it works well as in light coming in a window. I have
tried to obtain exactly the "lit fog" we have all seen around
street lights and such. It does not work. 

	I am about of the opinion that whatever this media is, it is not
what we would expect it to be from experience with this very
unsatisfactory reality of ours. I expect to see a halo around the
light source. I get the entire scene "lit" which is fine for fog
but I don't get the halo around the light source. 

	An interesting addition but still not what at least I am looking
for. 

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<blink>---please--don't---</blink>

http://www.giwersworld.org/artiii/

Oh my God! They've rendered Kenny!

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On Sun, 05 Sep 1999 03:03:50 -0400, Matt Giwer
<mgi### [at] giwersworldorg> wrote:

Media does take a lot of patience to learn. Although I do not consider
myself nearly as prominent in this field as are many others in these
groups, I'll be glad to try it out if you send me some relevant code
(the scale of the scene and media matter a lot). Or even better, post
it on this server and ask for help, somebody will surely lend a hand.


Peter Popov
ICQ: 15002700

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Matt Giwer wrote:
> 
>         But it has not been a long time.
> 
>         A nutshell. I have copied scattering media parameters from
> scenes where it works well as in light coming in a window. I have
> tried to obtain exactly the "lit fog" we have all seen around
> street lights and such. It does not work.
> 
>         I am about of the opinion that whatever this media is, it is not
> what we would expect it to be from experience with this very
> unsatisfactory reality of ours. I expect to see a halo around the
> light source. I get the entire scene "lit" which is fine for fog
> but I don't get the halo around the light source.
> 
>         An interesting addition but still not what at least I am looking
> for.

If you want a halo contained within a specific area think about placing
it into a container instead of filling the entire scene area with media.
I would suggest that you use two light sources withing your lamp. One
a point light with fade distance and fade power specified to limit
the area of radiation. This will give you the ability to fade the halo's
influence outwardly to make it appear to deminish. The second a spotlight
to add the cone of light one would expect coming from a lightsource. This
last is only useful if you have a lamp with a closed side like street lamps
with refector housings.

Like Peter I too am no master with the use of media and your milage may
vary.

-- 
Ken Tyler

See my 850+ Povray and 3D Rendering and Raytracing Links at:
http://home.pacbell.net/tylereng/index.html

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To get a halo around a light source, try changing the scattering model.
Isotropic scattering means that all the media which isn't in shadow will
be illuminated by the light, try something more angle dependant, like
Mie murky, which is type 3.
Also, use the fading feature of the light sources to get a better model
of illumination, although it also takes some time to get used to.
A good way to fake this glow around light sources is to put the
light_source at the center of a completely transparent sphere, and give
that sphere a highlight(I have always used specular, you might want to
try phong). Adjust the size and brightness of the highlight to do what
you want.

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Model 4 is probably best in this case, since it was meant to model the
scattering of gases.
And when using light fading, bear in mind that the scattering media itself also
attenuates light.

Margus

Chris Huff wrote:
> 
> To get a halo around a light source, try changing the scattering model.
> Isotropic scattering means that all the media which isn't in shadow will
> be illuminated by the light, try something more angle dependant, like
> Mie murky, which is type 3.
> Also, use the fading feature of the light sources to get a better model
> of illumination, although it also takes some time to get used to.
> A good way to fake this glow around light sources is to put the
> light_source at the center of a completely transparent sphere, and give
> that sphere a highlight(I have always used specular, you might want to
> try phong). Adjust the size and brightness of the highlight to do what
> you want.

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Matt Giwer wrote:
> 
>         But it has not been a long time.
> 
>         A nutshell. I have copied scattering media parameters from
> scenes where it works well as in light coming in a window. I have
> tried to obtain exactly the "lit fog" we have all seen around
> street lights and such. It does not work.
> 
>         I am about of the opinion that whatever this media is, it is not
> what we would expect it to be from experience with this very
> unsatisfactory reality of ours. I expect to see a halo around the
> light source. I get the entire scene "lit" which is fine for fog
> but I don't get the halo around the light source.
> 
>         An interesting addition but still not what at least I am looking
> for.
> 
	If you want to see how I did it (with fade_distance and fade_power),
the pic is at:
http://www.irtc.org/ftp/pub/stills/1999-08-31/jbhome.jpg
and the zipped source at:
http://www.irtc.org/ftp/pub/stills/1999-08-31/jbhome.zip

		Jerome

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* they'll tell you what can't * mailto:ber### [at] inamecom
* be done and why...          * http://www.enst.fr/~jberger
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