1.3.6.6 A more advanced example of scattering media

For a bit more advanced example of scattering media, let's make a room with a window and a light source illuminating from outside the room. The room contains scattering media, thus making the light beam coming through the window visible.

 global_settings { assumed_gamma 1 }
 camera { location <14.9, 1, -8> look_at -z angle 70 }
 light_source { <10,100,150>, 1 }
 background { rgb <0.3, 0.6, 0.9> }

 // A dim light source inside the room which does not
 // interact with media so that we can see the room:
 light_source { <14, -5, 2>, 0.5 media_interaction off }

 // Room
 union
 { difference
   { box { <-11, -7, -11>, <16, 7, 10.5> }
     box { <-10, -6, -10>, <15, 6, 10> }
     box { <-4, -2, 9.9>, <2, 3, 10.6> }
   }
   box { <-1.25, -2, 10>, <-0.75, 3, 10.5> }
   box { <-4, 0.25, 10>, <2, 0.75, 10.5> }
   pigment { rgb 1 }
 }
 
 // Scattering media box:
 box
 { <-5, -6.5, -10.5>, <3, 6.5, 10.25>
   pigment { rgbt 1 } hollow
   interior
   { media
     { scattering { 1, 0.07 extinction 0.01 }
       samples 30,100
     }
   }
 }

As suggested previously, the scattering color and extinction values were adjusted until the image looked good. In this kind of scene usually very small values are needed.

Note how the container box is quite smaller than the room itself. Container boxes should always be sized as minimally as possible. If the box were as big as the room much higher values for samples would be needed for a good result, thus resulting in a much slower rendering.