//scene shows an (incorrectly?) shaded bicubic_patch next to a correctly shaded disk with the light below them

bicubic_patch {     // This is lit-up on the side facing *away* from the light (bug?)
    type 1
    <-2, 0, -2>, <-1, 0, -2>, <1, 0, -2>, <2, 0, -2>,
    <-2, 0,  -1>, <-1, 0, -1>, <1, 0, -1>, <2, 0, -1>,
    <-2, 0, 1>, <-1, 0, 1>, <1, 0, 1>, <2, 0, 1>,
    <-2, 0, 2>, <-1, 0, 2>, <1, 0, 2>, <2, 0, 2>
    pigment { colour rgb<0, 1, 0> }
    translate <-2.2, 0, 0>
  }
  

disc {            // The side facing away from the light is in shadow, as would be expected
    <0, 0, 0>, <0, 1, 0>, 2
    pigment { colour rgb<0, 1, 0> }
    translate <2.2, 0, 0>
    }
  
  light_source {
  <0, -10, 0>  // put the light source *under* the bicubic_patch (and disk)
  colour rgb <1, 1, 1>
  }
  
  camera {   // look above the objects
  location <0.1, 6, -6>
  look_at <0.1, 0, 0>
  }