(* Copyright (c) 1993-1997, Silicon Graphics, Inc.
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 * GRAPHICS, INC.  BE LIABLE TO YOU OR ANYONE ELSE FOR ANY DIRECT,
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 * 
 * US Government Users Restricted Rights 
 * Use, duplication, or disclosure by the Government is subject to
 * restrictions set forth in FAR 52.227.19(c)(2) or subparagraph
 * (c)(1)(ii) of the Rights in Technical Data and Computer Software
 * clause at DFARS 252.227-7013 and/or in similar or successor
 * clauses in the FAR or the DOD or NASA FAR Supplement.
 * Unpublished-- rights reserved under the copyright laws of the
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 * Inc., 2011 N.  Shoreline Blvd., Mountain View, CA 94039-7311.
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 * OpenGL(R) is a registered trademark of Silicon Graphics, Inc.
 *)

(*  accpersp.ml
 *  Use the accumulation buffer to do full-scene antialiasing
 *  on a scene with perspective projection, using the special
 *  routines accFrustum() and accPerspective().
 *)

(* OCaml version by Florent Monnier *)

open GL
open Glu
open Glut

(* jitter

This is jitter point array for 8 jitters.

Values are floating point in the range -.5 < x < .5, -.5 < y < .5, and
have a gaussian distribution around the origin.

This is used to do model jittering for scene anti-aliasing and view volume
jittering for depth of field effects. Use in conjunction with the 
accwindow() routine.
*)

type jitter_point = { x: float; y: float }

(* 8 jitter points *)
let j8 =
  [|
      {x = -0.334818; y =  0.435331};
      {x =  0.286438; y = -0.393495};
      {x =  0.459462; y =  0.141540};
      {x = -0.414498; y = -0.192829};
      {x = -0.183790; y =  0.082102};
      {x = -0.079263; y = -0.317383};
      {x =  0.102254; y =  0.299133};
      {x =  0.164216; y = -0.054399};
  |]
;;

let pi = acos(-1.0) ;;

(* accFrustum()
 * The first 6 arguments are identical to the glFrustum() call.
 *  
 * pixdx and pixdy are anti-alias jitter in pixels. 
 * Set both equal to 0.0 for no anti-alias jitter.
 * eyedx and eyedy are depth-of field jitter in pixels. 
 * Set both equal to 0.0 for no depth of field effects.
 *
 * focus is distance from eye to plane in focus. 
 * focus must be greater than, but not equal to 0.0.
 *
 * Note that accFrustum() calls glTranslate().  You will 
 * probably want to insure that your ModelView matrix has been 
 * initialized to identity before calling accFrustum().
 *)
let accFrustum ~left ~right ~bottom
        ~top ~nnear ~ffar ~pixdx
        ~pixdy ~eyedx ~eyedy ~focus =

  let _, _, viewport_w, viewport_h = glGetInteger4 Get.GL_VIEWPORT in
	
  let xwsize = right -. left
  and ywsize = top -. bottom in
       
  let dx = -. (pixdx *. xwsize /. (float viewport_w) +. eyedx *. nnear /. focus)
  and dy = -. (pixdy *. ywsize /. (float viewport_h) +. eyedy *. nnear /. focus)
  in

  glMatrixMode GL_PROJECTION;
  glLoadIdentity();
  glFrustum (left +. dx) (right +. dx) (bottom +. dy) (top +. dy) (nnear) (ffar);
  glMatrixMode GL_MODELVIEW;
  glLoadIdentity();
  glTranslate (-. eyedx) (-. eyedy) (0.0);
;;


(* accPerspective()
 * 
 * The first 4 arguments are identical to the gluPerspective() call.
 * pixdx and pixdy are anti-alias jitter in pixels. 
 * Set both equal to 0.0 for no anti-alias jitter.
 * eyedx and eyedy are depth-of field jitter in pixels. 
 * Set both equal to 0.0 for no depth of field effects.
 *
 * focus is distance from eye to plane in focus. 
 * focus must be greater than, but not equal to 0.0.
 *
 * Note that accPerspective() calls accFrustum().
 *)
let accPerspective ~fovy ~aspect
        ~nnear ~ffar ~pixdx ~pixdy
        ~eyedx ~eyedy ~focus =

  let fov2 = ((fovy *. pi) /. 180.0) /. 2.0 in

  let top = nnear /. ((cos fov2) /. (sin fov2)) in
  let bottom = -. top;

  and right = top *. aspect in
  let left = -. right in

  accFrustum  left  right  bottom  top  nnear  ffar
              pixdx  pixdy  eyedx  eyedy  focus;
;;


(*  Initialize lighting and other values.  *)
let init() =
  let mat_ambient = (1.0, 1.0, 1.0, 1.0)
  and mat_specular = (1.0, 1.0, 1.0, 1.0)
  and light_position = (0.0, 0.0, 10.0, 1.0)
  and lm_ambient = (0.2, 0.2, 0.2, 1.0) in

  glMaterial GL_FRONT (Material.GL_AMBIENT mat_ambient);
  glMaterial GL_FRONT (Material.GL_SPECULAR mat_specular);
  glMaterial GL_FRONT (Material.GL_SHININESS 50.0);
  glLight (GL_LIGHT 0) (Light.GL_POSITION light_position);
  glLightModel (GL_LIGHT_MODEL_AMBIENT lm_ambient);
   
  glEnable GL_LIGHTING;
  glEnable GL_LIGHT0;
  glEnable GL_DEPTH_TEST;
  glShadeModel GL_FLAT;

  glClearColor 0.0 0.0 0.0 0.0;
  glClearAccum 0.0 0.0 0.0 0.0;
;;


let displayObjects() =
  let torus_diffuse = (0.7, 0.7, 0.0, 1.0)
  and cube_diffuse = (0.0, 0.7, 0.7, 1.0)
  and sphere_diffuse = (0.7, 0.0, 0.7, 1.0)
  and octa_diffuse = (0.7, 0.4, 0.4, 1.0) in

  glPushMatrix();
  glTranslate 0.0 0.0 (-5.0); 
  glRotate 30.0  1.0 0.0 0.0;

  glPushMatrix();
  glTranslate (-0.80) 0.35 0.0;
  glRotate 100.0  1.0 0.0 0.0;
  glMaterial GL_FRONT (Material.GL_DIFFUSE torus_diffuse);
  glutSolidTorus 0.275  0.85  16 16;
  glPopMatrix();

  glPushMatrix();
  glTranslate (-0.75) (-0.50) (0.0); 
  glRotate 45.0 0.0 0.0 1.0;
  glRotate 45.0 1.0 0.0 0.0;
  glMaterial GL_FRONT (Material.GL_DIFFUSE cube_diffuse);
  glutSolidCube (1.5);
  glPopMatrix();

  glPushMatrix();
  glTranslate 0.75 0.60 0.0;
  glRotate 30.0 1.0 0.0 0.0;
  glMaterial GL_FRONT (Material.GL_DIFFUSE sphere_diffuse);
  glutSolidSphere 1.0 16 16;
  glPopMatrix();

  glPushMatrix();
  glTranslate 0.70 (-0.90) 0.25;
  glMaterial GL_FRONT (Material.GL_DIFFUSE octa_diffuse);
  glutSolidOctahedron();
  glPopMatrix();

  glPopMatrix();
;;


let acsize = Array.length j8

let display() =
  let _, _, viewport_w, viewport_h = glGetInteger4 Get.GL_VIEWPORT in

  glClear [GL_ACCUM_BUFFER_BIT];
  for jitter = 0 to pred acsize do
    glClear [GL_COLOR_BUFFER_BIT; GL_DEPTH_BUFFER_BIT];
    accPerspective 50.0
        ((float viewport_w) /. (float viewport_h)) 
        1.0  15.0  j8.(jitter).x  j8.(jitter).y  0.0  0.0  1.0;
    displayObjects();
    glAccum GL_ACCUM (1.0 /. float acsize);
  done;
  glAccum GL_RETURN  1.0;
  glFlush();
;;


let reshape ~width:w ~height:h =
  glViewport 0 0 w h;
;;


let keyboard ~key ~x ~y =
  match key with
  | '\027' -> exit 0;
  | _ -> ()
;;


(*  Main Loop
 *  Be certain you request an accumulation buffer.
 *)
let () =
  ignore(glutInit Sys.argv);
  glutInitDisplayMode [GLUT_SINGLE; GLUT_RGB;
                       GLUT_ACCUM; GLUT_DEPTH];
  glutInitWindowSize 250 250;
  glutInitWindowPosition 100 100;
  ignore(glutCreateWindow Sys.argv.(0));
  init();
  glutReshapeFunc ~reshape;
  glutDisplayFunc ~display;
  glutKeyboardFunc ~keyboard;
  glutMainLoop();
;;