// uses image color index as height, extends along X-Z axes
// from <0 0 0> to <1 1 1>
height_field {
  png "plasma3.png"
  texture {
    pigment {
      image_map { png "plasma3.png" map_type 0 interpolate 2 once }
      rotate x*90 // lay X-Y image map down onto X-Z height field plane
    }
  }
}