// texture normal {} attribute
// create a texture that has a bumpiness corresponding to color index
// image maps into X-Y plane from <0,0,0> to <1,1,0>
bump_map
{ // uses image color or index as bumpiness
  gif "plasma3.gif" // the file to read (iff/gif/tga/dump/pot)
  map_type 0 // 0=planar, 1=spherical, 2=cylindrical, 5=torus
  interpolate 2 // 0=none, 1=linear, 2=bilinear, 4=normalized distance
  // [use_color | use_index]
  // [once]
  bump_size 0.5 // 0…3
} // bump_map