media {
          intervals integer
          samples min,max
          confidence float 1/128
          variance float 0.9
          ratio float 0.9
          absorption rgb <r,g,b>
          emission rgb <r,g,b>
          scattering { type, rgb <r,g,b> | extinction }
          density {
                    pattern
                    color_map { [ color_map ] } | density_map { [ density_map ] } }