let on_kbd ~key:k ~x:x ~y:y =
( match k with
| 113
| 27 -> exit 0
| 105 -> lx := !lx +. lstep ; Glut.postRedisplay ()
| 107 -> lx := !lx -. lstep ; Glut.postRedisplay ()
| 111 -> ly := !ly +. lstep ; Glut.postRedisplay ()
| 108 -> ly := !ly -. lstep ; Glut.postRedisplay ()
| 112 -> lz := !lz +. lstep ; Glut.postRedisplay ()
| 109 -> lz := !lz -. lstep ; Glut.postRedisplay ()
| 115 ->
grid_step := !grid_step +. 0.01; Visu.set_step_mb !grid_step ;
Glut.postRedisplay ()
| 122 ->
grid_step := !grid_step -. 0.01; Visu.set_step_mb !grid_step ;
Glut.postRedisplay ()
| 32 when !walk -> walk_step ()
| _ -> Printf.printf "Unknown key pressed: %d\n%!" k )