// uses image color index as height, extends along X-Z axes
// from <0 0 0> to <1 1 1>
height_field
{
  gif "plasma3.gif" // the file to read (gif/tga/pot)
//  inverse | texture {…} | color RGB
//  [smooth] // make smoother surface
//  [water_level N] // truncate/clip below N (0.0 ... 1.0)
// translate VECTOR | rotate VECTOR | scale VECTOR
}