How can I clarify the shadows that occur in scattering media after it hits
an object? In my scene these "dusty shadows" are nearly invisible! I'd like
to have rather sharp lines with good contrast to appear immediately after
the rays hit an object. Is that possible?  I really feel like I've tried it
all.

Regards,
Hugo

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"Hugo Asm" <hua### [at] post3teledk> wrote in message
news:3f3427f5$1@news.povray.org...
> How can I clarify the shadows that occur in scattering media after it hits
> an object? In my scene these "dusty shadows" are nearly invisible! I'd
like
> to have rather sharp lines with good contrast to appear immediately after
> the rays hit an object. Is that possible?  I really feel like I've tried
it
> all.

Maybe you haven't tried it all yet if 'extinction' hasn't been applied. Goes
in the scattering statement, and a low float value following it. This can
artificially enhance light's absorption transmission ratio, so the idea here
is to decrease that absorption and increase the transmission (well, this is
my interpretation). Closer to zero will brighten it up quite a bit in the
lit portions, hopefully leaving the shadows darker with more contrast
altogether. What might prove a problem still is that the whole media area
between the shadows and camera will also brighten, effectively fogging the
shadows again. The real answer might be to limit the media container to a
short distance toward the camera, leaving mostly empty space there. Possibly
a combination of the two things.

Bob H.

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In article <3f3427f5$1@news.povray.org>,
 "Hugo Asm" <hua### [at] post3teledk> wrote:

> How can I clarify the shadows that occur in scattering media after it hits
> an object? In my scene these "dusty shadows" are nearly invisible! I'd like
> to have rather sharp lines with good contrast to appear immediately after
> the rays hit an object. Is that possible?  I really feel like I've tried it
> all.

You don't give many details. I have no idea what your code looks like, 
but the fact that you are talking about a "dusty" effect makes me think 
you are using sampling method 1. Try increasing the number of samples, 
and using method 3.

-- 
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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Thanks for your replies! I still don't think the shadow-effect is too clear.
I've concentrated the light around the object in focus. I'm interested in a
discrete fog, not overwhelming in the picture. But then I can hardly see the
shadow effect. My eyes somehow expect a bit more. How can I exaggerate it?

I've posted a simplified version of the scene at p.text.scene-files.

Thanks,
Hugo

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"Hugo Asm" <hua### [at] post3teledk> wrote in message
news:3f36c8bf$1@news.povray.org...
> Thanks for your replies! I still don't think the shadow-effect is too
clear.
> I've concentrated the light around the object in focus. I'm interested in
a
> discrete fog, not overwhelming in the picture. But then I can hardly see
the
> shadow effect. My eyes somehow expect a bit more. How can I exaggerate it?
>
> I've posted a simplified version of the scene at p.text.scene-files.

Ahhh, now I understand what you were saying before. This is about visual
perceptions caused by the pupil dilating or contracting depending on the
amount of light present. I think you can usually see into a shadowed area
IRL a little better than you'd be able to do in a image on a computer
screen. That could account for the descrepency from what you see and what
you expect to see.

I tried a few changes to your script and basically got nowhere--- unless you
count my perceived notions of what I thought I was seeing. Not going to be
simple to have very thin dusty air and also a pronounced shadow. A possible
solution might be the usage of the light_group feature to create two
separate light sources shining into the media, with neither interacting
together and affecting the shadow differently. Alas, I had no luck with that
either. Take a look at my reply to your scene file posting at p.t.s-f.
group.

Bob H.

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> I tried a few changes to your script and basically got nowhere
> ---unless you count my perceived notions of what I thought I
> was seeing. Not going to be simple to have very thin dusty air
> and also a pronounced shadow.

Well, thanks for trying anyway.  :o)  I will postpone the media effect until
another time.

Best Regards,
Hugo

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Hugo Asm wrote:

> Thanks for your replies! I still don't think the shadow-effect is too clear.
> I've concentrated the light around the object in focus. I'm interested in a
> discrete fog, not overwhelming in the picture. But then I can hardly see the
> shadow effect. My eyes somehow expect a bit more. How can I exaggerate it?
> 
> I've posted a simplified version of the scene at p.text.scene-files.
> 
> Thanks,
> Hugo

Would it be possible to put a non-visible, but shadow producing object 
the same shape as the media in the same place?

I seem to recall hearing about this, but I admit I haven't tried it.

Tom A.

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