// set global atmospheric fog effect in the scene.
// at the fog distance, there will be 63% visibility
fog {
  fog_type 1               // 1=constant, 2=ground_fog
  distance 300
   // rgb - Red Green Blue color shortcut
     color rgb <0.7, 0.6, 0.6>
              // can also have 'filter' and 'transmit'
  // (---turbulence---)
  turbulence <0.5, 0.5, 1.0>
  turb_depth 0.8
  omega 0.5
  lambda 8.0
  octaves 6
  // (---ground fog---)
  fog_offset 0.4         // height of constant fog
  fog_alt 0.4            // at fog_offset+fog_alt: density=25%
}

fog {
  fog_type   2
  distance   0
  color      rgb 0.6 // gray
  fog_offset 0.7
  fog_alt    0.7
  turbulence 0.8
}


// An infinite planar surface
// plane {<A, B, C>, D } where: A*x + B*y + C*z = D
plane {
  y, // <X Y Z> unit surface normal, vector points "away from surface"
  -1.0 // distance from the origin in the direction of the surface normal
  hollow on // has an inside pigment?
  texture {
    pigment {
      checker
      color rgb <0.8, 0.8, 0.6>
      color rgb <1.0, 0.7, 0.5>
      scale 0.7
    }
  }
}

hollow on