type surface_result =
  { color: Point.t; kd: float; ks: float; phong: float }
  
type surface_function = 
  SurfFun of (int -> float -> float -> surface_result)
| SurfConst of surface_result
| SurfArray of surface_result array

type base_object_kind =
    Cone | Cube | Cylinder | Plane | Sphere

type base_object =
  { kind: base_object_kind;
    surf: surface_function;
    world2obj: Matrix.t;
    obj2world: Matrix.t;
    max_scale_applied : float;
  }
  
type obj_desc =
  Base of base_object
| Union of t * t
| Intersection of t * t
| Difference of t * t
| Null
  
and t = {    
    desc : obj_desc; 
    center : Point.t;
    radius : float;
  }

val print_base_object : base_object -> unit

val not_computed : Point.t
val obj_template : t
  
val cone: surface_function -> t
val cube: surface_function -> t
val cylinder: surface_function -> t
val plane: surface_function -> t
val sphere: surface_function -> t

val rotatex: t -> float -> t
val rotatey: t -> float -> t
val rotatez: t -> float -> t
val scale: t -> float -> float -> float -> t
val uscale: t -> float -> t
val translate: t -> float -> float -> float -> t

val difference: t -> t -> t
val intersect: t -> t -> t
val union: t -> t -> t

(* Return a normal unit vector at the given point on the given object.
   The point and the normal vector are in world coordinates. *)

val normal_vector: base_object -> Point.t -> int -> Vector.t