I thought a nice experiment would be to create a telescope to apply to the
Niagara images. When I did, the reults were surprising. I do not understand
Media enough to know why the media cirrus clods change the light in the
lense. Can anybody help? The only thing changed between renderings is the
cirrus clouds.

Here is the lens code:

#declare R = .00007 ;
#declare Lens =
        union{



                intersection{
                        sphere{<0,0,0>, R translate<0,0,-R/1.0071>}
                        sphere{<0,0,0>, R translate<0,0,R/1.0071>}
                        cylinder{<0,0,.005>,<0,0,-.005>,0.00002}

                        texture{pigment{rgbt<1,1,1,1>} }
                        interior{
                                ior 1.52

                        }
                }


                difference{
                        cylinder{<0,0,.0000005>,<0,0,-.0000005>,0.0000083}
                        cylinder{<0,0,.0000006>,<0,0,-.0000006>,0.00000785}
                        texture{T_Brass_3B}
                }

        }


Here is the cirrus cloud code straight out of Jamies Tierra inc file.


/*
  Persistence of Vision Ray Tracer Scene Description File

  Tierra v1.0 - Cirrus shell include

  --
  Jaime Vives Piqueres, Apr-May-Jun 2004.

*/

#if (use_cirrus)

// basic cloud pigment maped spherically
#declare d_base=
density{
   Cirrus_Density
   color_map{
     [0.00 rgb 0]
     [(1-Cirrus_Level) rgb 0]
     [(1-Cirrus_Level)+Cirrus_Border rgb 1]
     [1.00 rgb 1]
   }
   warp{spherical}
   // changing default orientation to match scene orientation
   rotate 90*x
   rotate 360*rand(r_clouds)*z
}

// density with a tiny layer of clouds
#declare d_clouds=
density{
 spherical
 density_map{
  [0.0 d_base]
  [Cirrus_Flatness d_base]
  [Cirrus_Flatness rgb 0]
  [1.0 rgb 0]
 }
}

// shell sphere with media cirrus
difference{
 sphere{0,1}
 sphere{0,1-Cirrus_Flatness}
 hollow
 texture{pigment{rgbt 1}}
 interior{
  media{
   intervals Clouds_Intervals
   absorption .04*5
   scattering{1,.04}
   density{d_clouds}
  }
 }
 // scale somewhat like earth in km
 scale 6800
 translate (-6800+Cirrus_Height)*y
}

#end




Thanks for your help,

Tim

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