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From: Tor Olav Kristensen
Subject: Inside the Crackle pattern (161KB)
Date: 18 Oct 2000 10:03:31
Message: <39ED7446.9FDB0DAA@hotmail.com>
Same method as for the image in my "Delving into the bozo world" post.
(But only monochrome colours this time.)

I'll post the source soon.


Tor Olav
--
mailto:tor### [at] hotmailcom
http://www.crosswinds.net/~tok/tokrays.html


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Attachments:
Download 'crackle01.jpg' (161 KB)

Preview of image 'crackle01.jpg'
crackle01.jpg


 

From: Jérôme M  Berger
Subject: Re: Inside the Crackle pattern (161KB)
Date: 18 Oct 2000 12:35:06
Message: <39ED98FA.3CD67965@enst.fr>
Tor Olav Kristensen wrote:
> 
> Same method as for the image in my "Delving into the bozo world" post.
> (But only monochrome colours this time.)
> 
> I'll post the source soon.
> 
	Nice, but I'd move the camera slightly up or down to avoid the
horizontal  dark line...

		Jérôme
-- 
********************************* Jérôme M. BERGER
* Abandon the search for truth, * mailto:ber### [at] inamecom
* Settle for a good fantasy.    * http://www.enst.fr/~jberger
*********************************


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From: Tor Olav Kristensen
Subject: Re: Inside the Crackle pattern => Source posted & Some problems (30KB + 28KB)
Date: 18 Oct 2000 15:30:35
Message: <39EDC0F6.9E6AFC2B@hotmail.com>
Tor Olav Kristensen wrote:

> ...
> I'll post the source soon.

I have now posted it to povray.text.scene-files:

http://news.povray.org/39EDBC5D.65D00C77%40hotmail.com


After studying the image, I have now found that there seems to
bee some problems with this rendering: Some of the spheres are
not completely round and some "false" odd shaped shadows
appear.

See the first attached image.
(Yellow arrows for cut spheres and red arrows for false shadows.)

Has anyone else seen these kind of errors with iso-surfaces before ?

If I remove my no_shadow keyword from the code, then many
more "odd shaped" shadows appear. See the last attached image.


Tor Olav
--
mailto:tor### [at] hotmailcom
http://www.crosswinds.net/~tok/tokrays.html


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Attachments:
Download 'isoerrors.jpg' (29 KB)
Download 'isoshadows.jpg' (31 KB)

Preview of image 'isoerrors.jpg'
isoerrors.jpg

Preview of image 'isoshadows.jpg'
isoshadows.jpg


 

From: Tor Olav Kristensen
Subject: Re: Inside the Crackle pattern (161KB)
Date: 18 Oct 2000 15:43:42
Message: <39EDC421.658BB2E6@hotmail.com>
"Jérôme M. Berger" wrote:

> ...
>        Nice, but I'd move the camera slightly up or down to avoid the
> horizontal  dark line...

When I first rendered this image I got 3 such lines.
Back then I decided that I would remove 2 of them (vertical).

I kind of liked the third one (the horizontal), so I kept it.

But now I agree with you -It too has to go.

Thank you for commenting.


Tor Olav
--
mailto:tor### [at] hotmailcom
http://www.crosswinds.net/~tok/tokrays.html


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From: Marc-Hendrik Bremer
Subject: Re: Inside the Crackle pattern => Source posted & Some problems (30KB + 28KB)
Date: 18 Oct 2000 16:08:26
Message: <39edcafa@news.povray.org>
Tor Olav Kristensen schrieb in Nachricht <39EDC0F6.9E6AFC2B@hotmail.com>...

>Has anyone else seen these kind of errors with iso-surfaces before ?
>


Yes, degenerated forms like your cut spheres. I decreased the accuracy-value
and everything was good ... well, not everything: Rendertime increased quite
a bit.

BTW: nice image!

Hope it helps,

Marc-Hendrik


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From: Marc-Hendrik Bremer
Subject: Re: Inside the Crackle pattern => Source posted & Some problems (30KB + 28KB)
Date: 18 Oct 2000 17:05:44
Message: <39edd868@news.povray.org>
Or wait ... wasn't it max_gradient? Yes, ... eval gave me some really big
values .... some percentages of that where enough to eliminate the visible
cuts (25 instead of 1045 or something like that).

Sorry

Marc-Hendrik

Marc-Hendrik Bremer schrieb in Nachricht <39edcafa@news.povray.org>...
>
>Tor Olav Kristensen schrieb in Nachricht <39EDC0F6.9E6AFC2B@hotmail.com>...
>
>>Has anyone else seen these kind of errors with iso-surfaces before ?
>>
>
>
>Yes, degenerated forms like your cut spheres. I decreased the
accuracy-value
>and everything was good ... well, not everything: Rendertime increased
quite
>a bit.
>
>BTW: nice image!
>
>Hope it helps,
>
>Marc-Hendrik
>


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From: Christoph Hormann
Subject: Re: Inside the Crackle pattern => Source posted & Some problems (30KB + 28KB)
Date: 18 Oct 2000 21:06:03
Message: <39EE10BA.B2DFA1CC@schunter.etc.tu-bs.de>
Tor Olav Kristensen wrote:
> 
[...]
> 
> After studying the image, I have now found that there seems to
> bee some problems with this rendering: Some of the spheres are
> not completely round and some "false" odd shaped shadows
> appear.
> 
> See the first attached image.
> (Yellow arrows for cut spheres and red arrows for false shadows.)
> 
> Has anyone else seen these kind of errors with iso-surfaces before ?
> 
> If I remove my no_shadow keyword from the code, then many
> more "odd shaped" shadows appear. See the last attached image.
> 

I had a quick look at the code, your isosurface function does have abrupt
changes of values and those often cause problems (i had problems when using
object_pattern in isosurface functions for example) increasing max_gradient or
accuracy might help, but in general functions with abrupt changes are not ideal
for isosurface functions.

Christoph

-- 
Christoph Hormann <chr### [at] gmxde>
Homepage: http://www.schunter.etc.tu-bs.de/~chris/


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From: Chris Huff
Subject: Re: Inside the Crackle pattern => Source posted & Some problems (30KB + 28KB)
Date: 18 Oct 2000 21:12:06
Message: <chrishuff-625AE5.16145218102000@news.povray.org>
In article <39EDC0F6.9E6AFC2B@hotmail.com>, Tor Olav Kristensen 
<tor### [at] hotmailcom> wrote:

> After studying the image, I have now found that there seems to
> bee some problems with this rendering: Some of the spheres are
> not completely round and some "false" odd shaped shadows
> appear.

In addition to the things mentioned by others(max_gradient, 
discontinuous functions...), you may be finding too few intersections. 
Try raising max_trace...maybe use "max_trace all_intersections". (going 
from memory here...I have never actually used this feature)

-- 
Christopher James Huff
Personal: chrishuff@mac.com, http://homepage.mac.com/chrishuff/
TAG: chr### [at] tagpovrayorg, http://tag.povray.org/

<><


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From: Steve
Subject: Re: Inside the Crackle pattern (161KB)
Date: 18 Oct 2000 23:16:22
Message: <slrn8usbi8.23e.steve@zero-pps.localdomain>
Now this looks like some sort of mythical ice cave. 

-- 
Cheers
Steve              email mailto:ste### [at] zeroppsuklinuxnet

%HAV-A-NICEDAY Error not enough coffee  0 pps. 

web http://www.zeropps.uklinux.net/

or  http://start.at/zero-pps

 11:50pm  up 8 days,  1:10,  2 users,  load average: 1.06, 1.08, 1.03


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From: Tor Olav Kristensen
Subject: Re: Inside the Crackle pattern => Source posted & Some problems (30KB + 28KB)
Date: 18 Oct 2000 23:41:04
Message: <39EE33F7.EBA08343@hotmail.com>
Marc-Hendrik Bremer wrote:

> Or wait ... wasn't it max_gradient? Yes, ... eval gave me some really big
> values .... some percentages of that where enough to eliminate the visible
> cuts (25 instead of 1045 or something like that).

I have just started a test rendering with max_gradient set to 150.
And it looks promising so far...

=)


Thanks !

Tor Olav
--
mailto:tor### [at] hotmailcom
http://www.crosswinds.net/~tok/tokrays.html


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