POV-Ray : Newsgroups : povray.documentation.inbuilt : radiosity and media : Re: radiosity and media Server Time
20 Jan 2022 12:13:04 EST (-0500)
  Re: radiosity and media  
From: Simon Copar
Date: 18 Apr 2013 19:25:01
Message: <web.51708070cb86620bf42173100@news.povray.org>
"Kenneth" <kdw### [at] gmailcom> wrote:
> Christian Froeschlin <chr### [at] chrfrde> wrote:
> > I tend to forget how they work together...
> >
> > There are different effects possible and it is not quite clear what
> > happens here. Can media get illuminated by radiosity? Does media reduce
> > the amount of light received by objects in the vicinity of an emitting
> > object? Does emissive media contribute light to radiosity calculations?
>
> There *was*/is a problem in POV-Ray with rad and media (in the current stable
> v3.62 release and earlier) which sort of contributes to the 'lack of clarity' in
> the docs. For object media (a sphere with a transparent pigment, for example),
> any other objects or parts thereof that are inside the media sphere do not
> receive radiosity lighting *from the media*--neither scattering nor emission
> types--but objects OUTSIDE it do. ('Atmospheric' media doesn't have this
> problem.) But it takes a rather particular/specialized test scene to show the
> effect; it's usually not grossly obvious, due to other scene objects also
> contributing rad light.

It does not work for me. What am I missing? My scene (stripped down to the bare
minimum) is below. The function {} might seem strange - it is generated
externally, designed to cover a certain object with fire (object not included).

I expected the floor to be at least faintly illuminated by the fire, but it
isn't.

My version is RC6 compiled as arch linux package (RC7 is not yet available in
the package form).

#version 3.7;
#declare CAM=<0,-10,1.5>;
camera {
  location CAM
  look_at <0,0,1.7>
  right x
  up (image_height/image_width)*z
  sky z
}


global_settings {
  max_trace_level 10
  assumed_gamma 2.2

  radiosity {
    brightness 1
    count 180
    pretrace_start 0.08
    pretrace_end 0.01
    recursion_limit 2
    media on
  }

}

plane {
  z,0
  texture {
    pigment {
      wrinkles
      color_map {
 [0 color rgb <0.35,0.2,0.1>]
 [0.5 color rgb <0.25,0.2,0.2>]
 [0.8 color rgb <0.09,0.075,0.075>]
      }
      turbulence 0.3
      scale <10,0.3,1>
    }
    normal {
      bumps 0.1
      scale <0.2,0.5,1>
    }
    finish {
      ambient 1
      diffuse 1.5
      specular 0.3
      roughness 0.02
    }
    rotate 37
  }
}



cylinder {
  <0,0,0.85>,<0,0,3.2>,1.9
  interior {
    media {
      intervals 2
      emission 1
      density {
 function {
   max(0,exp(-3*(z-(1.122814)))-0.5*exp(-6*(z-(1.122814)))
-8*(x-(-0.483531))*(x-(-0.483531))-8*(y-(-1.046504))*(y-(-1.046504)) )
   +max(0,exp(-3*(z-(1.126421)))-0.5*exp(-6*(z-(1.126421)))
-8*(x-(-0.367037))*(x-(-0.367037))-8*(y-(-0.759095))*(y-(-0.759095)) )
   +max(0,exp(-3*(z-(1.139738)))-0.5*exp(-6*(z-(1.139738)))
-8*(x-(-0.581356))*(x-(-0.581356))-8*(y-(-0.585519))*(y-(-0.585519)) )
   +max(0,exp(-3*(z-(1.179992)))-0.5*exp(-6*(z-(1.179992)))
-8*(x-(-0.596242))*(x-(-0.596242))-8*(y-(-0.749582))*(y-(-0.749582)) )
   +max(0,exp(-3*(z-(1.213622)))-0.5*exp(-6*(z-(1.213622)))
-8*(x-(-0.358601))*(x-(-0.358601))-8*(y-(-0.733758))*(y-(-0.733758)) )
   +max(0,exp(-3*(z-(1.229194)))-0.5*exp(-6*(z-(1.229194)))
-8*(x-(-0.873088))*(x-(-0.873088))-8*(y-(-1.011451))*(y-(-1.011451)) )
   +max(0,exp(-3*(z-(1.243289)))-0.5*exp(-6*(z-(1.243289)))
-8*(x-(-0.496820))*(x-(-0.496820))-8*(y-(-0.302525))*(y-(-0.302525)) )
   +max(0,exp(-3*(z-(1.244577)))-0.5*exp(-6*(z-(1.244577)))
-8*(x-(-0.989911))*(x-(-0.989911))-8*(y-(-0.673642))*(y-(-0.673642)) )
   +max(0,exp(-3*(z-(1.250126)))-0.5*exp(-6*(z-(1.250126)))
-8*(x-(-0.588272))*(x-(-0.588272))-8*(y-(0.369979))*(y-(0.369979)) )
 }
 color_map {
   [0.2 color rgb 0]
   [0.5 color rgb <0.3,0,0>]
   [0.8 color rgb <1,1,0>]
   [0.9 color rgb 2*<1,1,1>]
 }
 warp {
   turbulence 0.44
   lambda 2
   omega 0.7
   octaves 3
 }
      }

    }
  }
  texture {
    pigment { color rgbft 1 }
  }
  hollow
}


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