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From: Gail Shaw
Subject: Strange media effect. (20kbu)
Date: 3 Aug 2000 03:59:00
Message: <39892644@news.povray.org>
I was trying to get a fog-like effect with media, unfortunatly
I got the following picture. I thought initially that there was a non-hollow
object interfearing with the media, fog type 2 (ground fog) works fine.
The media container is definatly hollow.

The second picture is the same scene using fog type 2. That is what I want
to get with media

I've been fighting with this for two weeks now and I'm out of
ideas. I've posted the source for the simplified scene in p.b.s-f

If anyone can tell me what the problem is, I will be very grateful.

(Bill I have a feeling I'll need one of your signs)

Thanks

Gail
********************************************************************
* gsh### [at] monotixcoza              * Reality.dat not found         *
* http://www.rucus.ru.ac.za/~gail/ * Attempting to reboot universe *
********************************************************************
* The best way to accelerate Windows NT is at 9.8 m/s^2      *
********************************************************************


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Attachments:
Download 'StrangeMedia.jpg' (13 KB) Download 'WithFog.jpg' (8 KB)

Preview of image 'StrangeMedia.jpg'
StrangeMedia.jpg

Preview of image 'WithFog.jpg'
WithFog.jpg


 

From: David Heys
Subject: Re: Strange media effect. (20kbu)
Date: 3 Aug 2000 05:02:51
Message: <3989353b@news.povray.org>
> If anyone can tell me what the problem is, I will be very grateful.

Your problem lies in trying to get absorption, emission and scattering all
in the same media statement. You need to declare each media type separately
within the interior statement. I've listed out below how to get it to work.
BTW, having all three really slows things down. I'd use emission for test
purposes and then try different combinations of the three to get a final
effect.

David


#declare Final=1;

// ground fog
#if (Final=0)
 fog {
  fog_type   2
  distance   0.3
  color      rgb 0.7 // gray
  fog_offset -0.7
  fog_alt    0.15
  turbulence 1.5
  turb_depth 0.8
 }
#else
 box

  <-15,-3,-15>,<15,-0.3,45>
  pigment { rgbf 1 }
  hollow
  interior {
   media {
    absorption 0.7
    method 3
    density {
     bozo
     density_map {
      [0 rgb 1]
      [1 rgb 1]
     }
    }
   }
   media {
    emission 0.7
    method 3
    density {
     bozo
     density_map {
      [0 rgb 1]
      [1 rgb 1]
     }
    }
   }
   media {
    scattering {2, rgb<.25,.25,.25> extinction 1 }
    intervals 1 samples 1
    confidence 0.8 variance 1/32
    method 3
    density {
     gradient y
     color_map {
      [0 rgb 1]
      [1 rgb 1]
     }
    }
   }
  }
 }
#end


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From: ryan constantine
Subject: Re: Strange media effect. (20kbu)
Date: 3 Aug 2000 16:46:20
Message: <3989D9F9.F910706@yahoo.com>
wasn't there a section in the docs about multiple media and multiple
density?  does this apply here?  is that what the problem was?


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From: Peter Popov
Subject: Re: Strange media effect. (20kbu)
Date: 3 Aug 2000 17:10:35
Message: <nu0jos4spbijc1m8ogvvsioqn53tnb8200@4ax.com>
On Thu, 3 Aug 2000 00:55:03 -0800, "David Heys" <sou### [at] gcinet>
wrote:

>> If anyone can tell me what the problem is, I will be very grateful.
>
>Your problem lies in trying to get absorption, emission and scattering all
>in the same media statement. You need to declare each media type separately
>within the interior statement. I've listed out below how to get it to work.

Using emission, absorption and scattering in a single media statement
is perfectly legal. However, they will share the same density which
will render them rather useless (unless the density is totally
unsaturated, color-wise).

>BTW, having all three really slows things down. 

Only true a) for scattering and b) for separate media statements.


Peter Popov ICQ : 15002700
Personal e-mail : pet### [at] usanet
TAG      e-mail : pet### [at] tagpovrayorg


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From: Peter Popov
Subject: Re: Strange media effect. (20kbu)
Date: 3 Aug 2000 17:10:36
Message: <961josgklq8m3mv5ahg1qqaut1aqubdno1@4ax.com>
On Thu, 3 Aug 2000 09:57:33 +0200, "Gail Shaw" <gsh### [at] monotixcoza>
wrote:

>If anyone can tell me what the problem is, I will be very grateful.

Looks like there're too few samples. Try starting with 5 or 10 and
then use anti-aliasing along the way.


Peter Popov ICQ : 15002700
Personal e-mail : pet### [at] usanet
TAG      e-mail : pet### [at] tagpovrayorg


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From: Gail Shaw
Subject: Re: Strange media effect. (20kbu)
Date: 4 Aug 2000 03:16:23
Message: <398a6dc7@news.povray.org>
Peter Popov wrote in message <961josgklq8m3mv5ahg1qqaut1aqubdno1@4ax.com>...
>On Thu, 3 Aug 2000 09:57:33 +0200, "Gail Shaw" <gsh### [at] monotixcoza>
>wrote:
>
>>If anyone can tell me what the problem is, I will be very grateful.
>
>Looks like there're too few samples. Try starting with 5 or 10 and
>then use anti-aliasing along the way.
>


I feel really dumb now.

<rereads mega documentation> Mega creates extra intervals not
extra samples.

I had an odd idea that only one sample was needed and more would be created
as necessary.

Thanks for the help Peter. Pic looks a lot better now.

Gail
********************************************************************
* gsh### [at] monotixcoza              * Reality.dat not found         *
* http://www.rucus.ru.ac.za/~gail/ * Attempting to reboot universe *
********************************************************************
* The best way to accelerate Windows NT is at 9.8 m/s^2      *
********************************************************************


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From: Peter Popov
Subject: Re: Strange media effect. (20kbu)
Date: 4 Aug 2000 05:20:55
Message: <gf2los4rl7a8mldaih4s1ec8ksnligkj8g@4ax.com>
On Fri, 4 Aug 2000 09:14:59 +0200, "Gail Shaw" <gsh### [at] monotixcoza>
wrote:

>I feel really dumb now.

I would let you have my sign but I need it as I've made the same
mistake a couple of weeks ago. It was more obvious in my case, though.

>I had an odd idea that only one sample was needed and more would be created
>as necessary.

That's how antialiasing works. However, in order to be able to get a
sample in-between two others, MegaPOV will need, well, at least two
others :)


Peter Popov ICQ : 15002700
Personal e-mail : pet### [at] usanet
TAG      e-mail : pet### [at] tagpovrayorg


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From: Jerome M  Berger
Subject: Re: Strange media effect. (20kbu)
Date: 4 Aug 2000 05:47:47
Message: <398A9141.210183CE@iname.com>
Peter Popov wrote:
> 
> That's how antialiasing works. However, in order to be able to get a
> sample in-between two others, MegaPOV will need, well, at least two
> others :)
> 
	Actually, if you tell it to use only one or two samples
with method 3, it will take three and work from there...

		Jerome
-- 

* Doctor Jekyll had something * mailto:ber### [at] inamecom
* to Hyde...                  * http://www.enst.fr/~jberger
*******************************


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From: Jerome M  Berger
Subject: Re: Strange media effect. (20kbu)
Date: 4 Aug 2000 05:48:52
Message: <398A9182.66C040B7@iname.com>
Gail Shaw wrote:
> 
> I was trying to get a fog-like effect with media, unfortunatly
> I got the following picture. I thought initially that there was a non-hollow
> object interfearing with the media, fog type 2 (ground fog) works fine.
> The media container is definatly hollow.
> 
> The second picture is the same scene using fog type 2. That is what I want
> to get with media
> 
> I've been fighting with this for two weeks now and I'm out of
> ideas. I've posted the source for the simplified scene in p.b.s-f
> 
> If anyone can tell me what the problem is, I will be very grateful.
> 
> (Bill I have a feeling I'll need one of your signs)
> 
> Thanks
> 
	What version of MegaPov where you using?

		Jerome
-- 

* Doctor Jekyll had something * mailto:ber### [at] inamecom
* to Hyde...                  * http://www.enst.fr/~jberger
*******************************


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From: Gail Shaw
Subject: Re: Strange media effect. (20kbu)
Date: 4 Aug 2000 06:03:15
Message: <398a94e3@news.povray.org>
Jerome M. Berger wrote in message <398A9182.66C040B7@iname.com>...
>Gail Shaw wrote:
>>
>>
> What version of MegaPov where you using?


0.5a

Works fine now that I put the samples to 10.


Gail
********************************************************************
* gsh### [at] monotixcoza              * Reality.dat not found         *
* http://www.rucus.ru.ac.za/~gail/ * Attempting to reboot universe *
********************************************************************
* The best way to accelerate Windows NT is at 9.8 m/s^2      *
********************************************************************


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