// Consider the differences in this scene if you add fog.
// IMHO fog (rgb 0) should make everything darker, no?

light_source {<14,2,-3> rgb 1}

box{<-500,-5,-500>,<500,-1,500> pigment {bozo scale 20}}

plane{y,-.025 pigment{rgbt 0.8}
        hollow
        interior{
                media{
                        scattering{ 1, rgb <0.25,0.5,1>               }
                      }}}


//UN comment out this line below.
//fog{ rgb 0 distance 15 fog_type 2
                }

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On Fri, 8 Feb 2002 15:04:33 -0500, Greg M. Johnson wrote:
> // Consider the differences in this scene if you add fog.
> // IMHO fog (rgb 0) should make everything darker, no?

I'm not where I can look at what the results of this are and what you
think they should be, but I was wondering if you get the same result
if you put the media in a finite container.

-- 
#macro R(L P)sphere{L F}cylinder{L P F}#end#macro P(V)merge{R(z+a z)R(-z a-z)R(a
-z-z-z a+z)torus{1F clipped_by{plane{a 0}}}translate V}#end#macro Z(a F T)merge{
P(z+a)P(z-a)R(-z-z-x a)pigment{rgbf 1}hollow interior{media{emission 3-T}}}#end 
Z(-x-x.2x)camera{location z*-10rotate x*90normal{bumps.02scale.05}}

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"Ron Parker" <ron### [at] povrayorg> wrote in message
news:slr### [at] fwicom...
> On Fri, 8 Feb 2002 15:04:33 -0500, Greg M. Johnson wrote:
> > // Consider the differences in this scene if you add fog.
> > // IMHO fog (rgb 0) should make everything darker, no?
>
> I'm not where I can look at what the results of this are and what you
> think they should be, but I was wondering if you get the same result
> if you put the media in a finite container.

Tried it here and got a bizzare effect, the background turned pure red when
fog is there.  However the fog works as expected.  Reason the red is a
strange thing to see is that neither media nor fog should be influencing the
background.
And yes, both plane or box used to check on that.  fog seems to be as I'd
expect, like I said, but it's the fog addition making the entire background
red.

Double-check shows it's actually only the lower half of the scene that turns
red, but even with all else white or colorless, regardless.  All that
factors is the use of fog or not, but if  fog_alt .00001 fog_offset .00001
is used things return to normal.

Keep in mind that the scattering media tends toward white while the ground
fog tends toward black, cancelling each other out somewhat.
Don't know if lack of the fog parameters could be considered a bug.  But
maybe Greg is seeing something altogether different there.

Still beta 10 here, not 11 yet.

bob h

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On Fri, 8 Feb 2002 21:33:47 -0600, bob h wrote:
> Tried it here and got a bizzare effect, the background turned pure red when
> fog is there.  However the fog works as expected.  Reason the red is a

FWIW, I don't see this, but I'm using something newer than beta 11.

-- 
#local R=<7084844682857967,0787982,826975826580>;#macro L(P)concat(#while(P)chr(
mod(P,100)),#local P=P/100;#end"")#end background{rgb 1}text{ttf L(R.x)L(R.y)0,0
translate<-.8,0,-1>}text{ttf L(R.x)L(R.z)0,0translate<-1.6,-.75,-1>}sphere{z/9e3
4/26/2001finish{reflection 1}}//ron.parker@povray.org My opinions, nobody else's

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Wasn't it Greg M. Johnson who wrote:
>// Consider the differences in this scene if you add fog.
>// IMHO fog (rgb 0) should make everything darker, no?

Is this the same as this known bug?

        media & fog bug?
        (Thorsten doesn't like the confirmation)
        http://news.povray.org/3c1379e0$1@news.povray.org

-- 
Mike Williams
Gentleman of Leisure

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"Mike Williams" <mik### [at] nospamplease> wrote in message
news:B1g### [at] econymdemoncouk...
> Wasn't it Greg M. Johnson who wrote:
> >// Consider the differences in this scene if you add fog.
> >// IMHO fog (rgb 0) should make everything darker, no?
>
> Is this the same as this known bug?
>
>         media & fog bug?
>         (Thorsten doesn't like the confirmation)
>         http://news.povray.org/3c1379e0$1@news.povray.org

I don't think so.  I shortened that scene and found it's the shadow of the
box container not mixing well with the fog as usual, still the same in beta
11 as all previous versions of POV I believe.

// buggy fog scene

#declare FogSw=1; // 1=on, 0=off
#declare MediaSw=1; //1=on, 0=off

camera {
  location <0,2,-10>
  look_at <0,0,0>
}

light_source {
  <0,9999,0>
  color rgb 1
}

#if(FogSw)
fog {
  fog_type 2
  distance 200
  fog_offset 0
  fog_alt 10
  color rgb 1
}
#end

#if(MediaSw)
box {
  <-10,10,-10>
  <10,20,10>
  material {
    texture {
  // try just 1 transparency and shadow of box begins to show
      pigment {rgbf 1.012345}
    }
    interior {
      media {
        scattering {1, 0} // no scattering(?)
        density {
          rgb 0 // no density(?)
        }
      }
    }
  }
  hollow
}
#end

plane {y,0 texture {pigment {rgb 1}}}

// END

The thing Greg was seeing seemed to be the opposite.  No darkening being
seen by a black fog spread over top of a media filled plane (the above
script has media above fog instead).
Anyway, I did see the correct* behavior in beta 10 and now still so in 11.
So I don't know what's up about that.

* And to repeat, from the horizon line and upward I see a red color which
ought not be there since no object is above -0.25*y, however the fog would
be.  Just shouldn't be solid red!  Very odd...

bob h

See changed script:

light_source {<14,2,-3> rgb 1}

box{<-500,-5,-500>,<500,-1,500> pigment {bozo scale 20}}

plane{y,-.025 pigment{rgbt 0.8}
        hollow
        interior{
                media{
                        scattering{ 1, rgb <0.25,0.5,1>}
                      }}}

fog{ rgb -.5 // darkened even further
         distance 15 fog_type 2
//fog_alt 1 fog_offset 1 // added this to fix red sky
}

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