POV-Ray : Newsgroups : povray.binaries.images : Media intervals Server Time
18 Nov 2024 08:14:57 EST (-0500)
  Media intervals (Message 1 to 6 of 6)  
From: Tim Nikias v2 0
Subject: Media intervals
Date: 1 Jun 2004 05:35:45
Message: <40bc4df1@news.povray.org>
My "A Rose" image is ready and off to print. Still, using 75 intervals for
the final render at 3200x2400 showed these "layering" artifacts on close-up
of the clouds. Looks much like "stacked planes technique" here, and I guess
this is due to how the intervals are spread across the interior of the
object: they sample at the same layers.

Anyways, I've used method 2 for this one, with 75 intervals and 1,1 min- and
max-samples. The Docs say that using different sample-values would lead to
random noise much like the initial method 1 of POV 3.1g. I want to
experiment a little with it later on to see if I can exploit the randomness
to hide the "mathematicalness" of media in future images. First though, I
wanted to ask here if anyone has similiar experiences and already has some
tricks up his sleeve which he/she might want to share with us?

Regards,
Tim

-- 
"Tim Nikias v2.0"
Homepage: <http://www.nolights.de>


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From: Xplo Eristotle
Subject: Re: Media intervals
Date: 1 Jun 2004 11:08:54
Message: <40bc9c06@news.povray.org>
Tim Nikias v2.0 wrote:
> 
> Anyways, I've used method 2 for this one...

Er. Why not use method 3?

-Xplo


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From: Tim Nikias v2 0
Subject: Re: Media intervals
Date: 1 Jun 2004 12:14:50
Message: <40bcab7a@news.povray.org>
> > Anyways, I've used method 2 for this one...
>
> Er. Why not use method 3?

Is there much difference when comparing
method 2 intervals 75 samples 1,1
to
method 3 intervals 1 samples 75,75?

I'm not 100% sure, but AFAIK, there isn't. On some objects (especially where
interior areas follow in succession) method 3 creates artifacts, hence my
reliance on method 2, even though the use here would have allowed method 3.
I want to work with method 2 because of above mentioned artifacts, so...

-- 
"Tim Nikias v2.0"
Homepage: <http://www.nolights.de>


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From: "Jérôme M. Berger"
Subject: Re: Media intervals
Date: 1 Jun 2004 13:51:32
Message: <40bcc224@news.povray.org>
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Tim Nikias v2.0 wrote:
|>>Anyways, I've used method 2 for this one...
|>
|>Er. Why not use method 3?
|
|
| Is there much difference when comparing
| method 2 intervals 75 samples 1,1
| to
| method 3 intervals 1 samples 75,75?
|
	No, but to get full use of the method 3, you shouldn't set the same
number for min samples and max samples. The whole point of method 3 is
that it starts with min samples and adds more where they are needed.

	You might also want to take a look at MegaPov 0.7 and the
sample_spacing keyword. It causes the media to be sampled more in
parts of the render where the ray travels a longer way through the
media. In your scene, that means that more samples will get taken near
the horizon (where I assume the banding will be harder to get rid of).

		Jerome
- --
******************************
*      Jerome M. Berger      *
* mailto:jbe### [at] ifrancecom *
*  http://jeberger.free.fr/  *
******************************
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From: Tim Nikias v2 0
Subject: Re: Media intervals
Date: 1 Jun 2004 13:56:51
Message: <40bcc363$1@news.povray.org>
> No, but to get full use of the method 3, you shouldn't set the same
> number for min samples and max samples. The whole point of method 3 is
> that it starts with min samples and adds more where they are needed.

I know, just in recent attempts I've noticed that I had to set min-samples
quiet high to get good results, probably because I'm using pretty extreme
settings for my media. I'm not sure how method 3 figures if it should raise
the samples, but I guess that extreme details and small-scale densities
aren't easy to handle for such an algorithm. So, along with the mentioned
artifacts, I've turned to method 2, as I have a more definite idea of what
I'm doing when I'm changing values. Hence this thread, I want to get some
more knowledge of it and figure how to do things different to achieve better
effects.

> You might also want to take a look at MegaPov 0.7 and the
> sample_spacing keyword. It causes the media to be sampled more in
> parts of the render where the ray travels a longer way through the
> media. In your scene, that means that more samples will get taken near
> the horizon (where I assume the banding will be harder to get rid of).

MegaPOV... I've only used it once to get a look at isosurfaces before 3.5
came out, aside of that, I like to stick to the official version.

Tim

-- 
"Tim Nikias v2.0"
Homepage: <http://www.nolights.de>


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From: Slime
Subject: Re: Media intervals
Date: 1 Jun 2004 14:14:47
Message: <40bcc797$1@news.povray.org>
> Anyways, I've used method 2 for this one

Bad choice if you ask me. Prefer method 3 to method 2; method 3 makes an
effort to clear up the type of artifacts you're getting. You might even try
method 1; graininess is much better than the artifacts you're getting (IMO).

Otherwise, just make sure your media container is as tightly enclosed around
the clouds as possible.

 - Slime
 [ http://www.slimeland.com/ ]


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