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From: St 
Subject: Fog > Light > Shadows
Date: 17 May 2007 03:34:04
Message: <464c056c@news.povray.org>
Hi all

   Need a little help and advice if possible.

   I'm creating a scene that uses ground fog, and I'm getting blue shadows 
cast from my objects. This doesn't look right to me, but then again, I can't 
say that I've ever seen a shadow in fog. I'm using one area_light with 
colour rgb 0.6.

   What would be the normal behaviour of light and then shadows in a fog 
scene? What would be the best way to approach this, (as in, should there be 
shadows at all, and what colour should they be if yes)?

      ~Steve~


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From: Alain
Subject: Re: Fog > Light > Shadows
Date: 17 May 2007 06:04:06
Message: <464c2896$1@news.povray.org>
St. nous apporta ses lumieres en ce 17 / 05 / 2007 03:33:
> Hi all
> 
>    Need a little help and advice if possible.
> 
>    I'm creating a scene that uses ground fog, and I'm getting blue shadows 
> cast from my objects. This doesn't look right to me, but then again, I can't 
> say that I've ever seen a shadow in fog. I'm using one area_light with 
> colour rgb 0.6.
> 
>    What would be the normal behaviour of light and then shadows in a fog 
> scene? What would be the best way to approach this, (as in, should there be 
> shadows at all, and what colour should they be if yes)?
> 
>       ~Steve~
> 

If you look in the documentation, you'll see that fog don't interact with light.
How does your shadows look without the fog in your scene? Dou you use a blue 
fill light? Is your fog coloured? All of those can make the shadows blue.

-- 
Alain
-------------------------------------------------
EVERYTHING HAS A GENDER

You may not know this but many nonliving things have a gender...

A Web Page is Female, because it's always getting hit on.


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From: St 
Subject: Re: Fog > Light > Shadows
Date: 17 May 2007 07:21:48
Message: <464c3acc$1@news.povray.org>
"Alain" <ele### [at] netscapenet> wrote in message 
news:464c2896$1@news.povray.org...
> St. nous apporta ses lumieres en ce 17 / 05 / 2007 03:33:
> If you look in the documentation, you'll see that fog don't interact with 
> light.
> How does your shadows look without the fog in your scene? Dou you use a 
> blue fill light? Is your fog coloured? All of those can make the shadows 
> blue.


    I've posted a couple of examples in p.b.i Alain. The shadow without the 
fog looks normal to me, (maybe too dark though), and I'm not using a fill 
light. My fog colour is the same as my light colour, rgb 0.6. I'm just 
wondering if it's to do with the height of my light, as it's only 70 units 
high. Would it be better if I used something that more resembles the sun?

    ~Steve~




> -- 
> Alain


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From: St 
Subject: Re: Fog > Light > Shadows
Date: 17 May 2007 09:24:38
Message: <464c5796$1@news.povray.org>
>I'm just wondering if it's to do with the height of my light, as it's only 
>70 units
> high.

   Hmm, no, it's not the height, that just sharpens the shadow.

    ~Steve~


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From: Mike Raiford
Subject: Re: Fog > Light > Shadows
Date: 17 May 2007 09:37:53
Message: <464c5ab1$1@news.povray.org>
St. wrote:
>> I'm just wondering if it's to do with the height of my light, as it's only 
>> 70 units
>> high.
> 
>    Hmm, no, it's not the height, that just sharpens the shadow.
> 

Is it possible to post a minimal scene that reproduces the blue 
shadow..? I'm curious, now.


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From: St 
Subject: Re: Fog > Light > Shadows
Date: 17 May 2007 10:01:04
Message: <464c6020$1@news.povray.org>
"Mike Raiford" <mra### [at] hotmailcom> wrote in message 
news:464c5ab1$1@news.povray.org...

> Is it possible to post a minimal scene that reproduces the blue shadow..? 
> I'm curious, now.

  I think it's my assumed_gamma Mike. I've just tried it with 2.2 which 
makes the whole image too dark (but the shadow looks ok), and 1, and that's 
better, but still too dark, (now with a darker blue shadow). At .75, the 
overall image looks fine, (the right brightness, contrast, etc.), apart from 
the blue shadow.

  Hmm, what to do, what to do...

   ~Steve~



  global_settings {
  assumed_gamma .75 max_trace_level 60 }

fog {
  fog_type   2
  distance   75
  colour      rgb 0.6
  fog_offset 0.005
  fog_alt    0.2
  turbulence 1
  turb_depth .5
  }

light_source {
  0*x
  colour rgb 0.6
  area_light
  <8, 0, 2> <2, 0, 8>
  4, 4
  adaptive 0
  jitter
  circular
  translate <30, 70, -30>
  }


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From: Mike Raiford
Subject: Re: Fog > Light > Shadows
Date: 17 May 2007 11:08:38
Message: <464c6ff6@news.povray.org>
St. wrote:
> "Mike Raiford" <mra### [at] hotmailcom> wrote in message 
> news:464c5ab1$1@news.povray.org...
> 
>> Is it possible to post a minimal scene that reproduces the blue shadow..? 
>> I'm curious, now.
> 
>   I think it's my assumed_gamma Mike. I've just tried it with 2.2 which 
> makes the whole image too dark (but the shadow looks ok), and 1, and that's 
> better, but still too dark, (now with a darker blue shadow). At .75, the 
> overall image looks fine, (the right brightness, contrast, etc.), apart from 
> the blue shadow.
> 
>   Hmm, what to do, what to do...
> 
>    ~Steve~


Hm. The code you included with this post doesn't exhibit much of 
anything, just a gray fog with a darker gray background.

What version of POVRay are you using?


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From: St 
Subject: Re: Fog > Light > Shadows
Date: 17 May 2007 12:16:27
Message: <464c7fdb$1@news.povray.org>
"Mike Raiford" <mra### [at] hotmailcom> wrote in message 
news:464c6ff6@news.povray.org...
> St. wrote:
>> "Mike Raiford" <mra### [at] hotmailcom> wrote in message 
>> news:464c5ab1$1@news.povray.org...

> Hm. The code you included with this post doesn't exhibit much of anything, 
> just a gray fog with a darker gray background.

  That's all there is apart from Wings models and some PovTree's. As it is 
now, the scene looks quite good and I'm happy with it, I'm just not getting 
the assumed_gamma thing. It's confusing me because it should either be 2.2 
or 1 (from what I've read). FWIW, nearly all of my images over the last two 
years use a low assumed_gamma. Where am I going wrong with this?

>
> What version of POVRay are you using?

      Yes, sorry, 3.5.

    ~Steve~


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From: Tim Attwood
Subject: Re: Fog > Light > Shadows
Date: 17 May 2007 22:49:10
Message: <464d1426@news.povray.org>
Are you using radiosity? A blue sky
can tint the fog blue if you are using
radiosity.

What are the textures? Are any reflective?


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From: St 
Subject: Re: Fog > Light > Shadows
Date: 18 May 2007 02:44:01
Message: <464d4b31$1@news.povray.org>
"Tim Attwood" <tim### [at] comcastnet> wrote in message 
news:464d1426@news.povray.org...
> Are you using radiosity? A blue sky
> can tint the fog blue if you are using
> radiosity.

     No radiosity and I've removed my sky_sphere - no difference.


>
> What are the textures? Are any reflective?

     The textures are image maps with bump mapping and the only thing that's 
reflective is a small model which I don't think would make a difference.

     I've settled for having the assumed_gamma at 1.2, which makes the 
scene/shadow better, but darker overall.

      ~Steve~


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