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(* robot.ml
 * This program shows how to composite modeling transformations
 * to draw translated and rotated hierarchical models.
 * Interaction:  pressing the s and e keys (shoulder and elbow)
 * alters the rotation of the robot arm.
 *)

(* OCaml version by Florent Monnier *)

open GL
open Glu
open Glut

let shoulder = ref 0
let elbow = ref 0

let init() =
  glClearColor 0.0 0.0 0.0 0.0;
  glShadeModel GL_FLAT;
;;

let display() =
  glClear [GL_COLOR_BUFFER_BIT];
  glPushMatrix();
    glTranslate (-1.0) 0.0 0.0;
    glRotate (float !shoulder) 0.0 0.0 1.0;
    glTranslate 1.0 0.0 0.0;
    glPushMatrix();
      glScale 2.0 0.4 1.0;
      glColor3 1.0 0.4 0.0;
      glutWireCube 1.0;
    glPopMatrix();

    glTranslate 1.0 0.0 0.0;
    glRotate (float !elbow) 0.0 0.0 1.0;
    glTranslate 1.0 0.0 0.0;
    glPushMatrix();
      glScale 2.0 0.4 1.0;
      glColor3 0.0 0.8 1.0;
      glutWireCube 1.0;
    glPopMatrix();

  glPopMatrix();
  glutSwapBuffers();
;;


let reshape ~width:w ~height:h =
  glViewport 0 0 w h; 
  glMatrixMode GL_PROJECTION;
  glLoadIdentity();
  gluPerspective 65.0 ((float w)/.(float h)) 1.0 20.0;
  glMatrixMode GL_MODELVIEW;
  glLoadIdentity();
  glTranslate 0.0 0.0 (-5.0);
;;


let keyboard ~key ~x ~y =
  match key with
  | 's' ->
      shoulder := (!shoulder + 5) mod 360;
      glutPostRedisplay();
  | 'S' ->
      shoulder := (!shoulder - 5) mod 360;
      glutPostRedisplay();
  | 'e' ->
      elbow := (!elbow + 5) mod 360;
      glutPostRedisplay();
  | 'E' ->
      elbow := (!elbow - 5) mod 360;
      glutPostRedisplay();
  | 'Q' | 'q' | '\027' ->
      exit 0;
  | _ -> ()
;;


let () =
  ignore(glutInit Sys.argv);
  glutInitDisplayMode [GLUT_DOUBLE; GLUT_RGB];
  glutInitWindowSize 500 500;
  glutInitWindowPosition 100 100;
  ignore(glutCreateWindow Sys.argv.(0));
  init();
  glutDisplayFunc ~display; 
  glutReshapeFunc ~reshape;
  glutKeyboardFunc ~keyboard;
  glutMainLoop();
;;