// set viewer's position in the scene
camera
{
  location  <0.0,  1.0, -6.0> // <X Y Z>
  direction 2.0*z             // which way are we looking <X Y Z>
  up        y                 // which way is +up <X Y Z>
  right     4/3*x             // which way is +right <X Y Z> and aspect ratio
  look_at   <0.0,  0.0,  0.0> // point center of view at this point <X Y Z>
}