/* Gestion du tampon accumulation d'OpenGL      */
/*                                              */
/* Auteur: Nicolas JANEY                        */
/* nicolas.janey@univ-fcomte.fr                 */
/* Septembre 2009                               */

#include <stdio.h>

#include <GL/glut.h>
#include <GL/gl.h>
#include <GL/glu.h>

/* Variables et constantes globales             */
/* pour les angles et les couleurs utilises     */

static float rx = 0.0F;
static float ry = 0.0F;
static float rz = 0.0F;

#define ACSIZE 4

GLfloat dx[ACSIZE],dy[ACSIZE];

GLfloat jitter4[4][2] = {
  {10.0F,10.0F},
  {10.0F,-10.0F},
  {-10.0F,-10.0F},
  {-10.0F,10.0F},
};

void loaddxdy(void) {
  long i;
  for (i = 0; i < ACSIZE; i++) {
    dx[i] = jitter4[i][0]*10/glutGet(GLUT_WINDOW_WIDTH);
    dy[i] = jitter4[i][1]*10/glutGet(GLUT_WINDOW_HEIGHT); }
}

void myinit(void) {
  GLfloat blanc[] = { 1.0F,1.0F,1.0F,1.0F };
  GLfloat grisMoyen[] = { 0.5F,0.5F,0.5F,1.0F };
  GLfloat grisClair[] = { 0.8F,0.8F,0.8F,1.0F };
  GLfloat grisFonce[] = { 0.2F,0.2F,0.2F,1.0F };
  GLfloat position[] = { 0.0F,2.0F,2.0F,0.0F };
  GLfloat mat_shininess[] = { 50.0F };
  GLfloat lmodel_ambient[] = { 0.2F,0.2F,0.2F,1.0F };
  glEnable(GL_DEPTH_TEST);
  glDepthFunc(GL_LESS);
  glLightfv(GL_LIGHT0,GL_AMBIENT,grisMoyen);
  glLightfv(GL_LIGHT0,GL_DIFFUSE,blanc);
  glLightfv(GL_LIGHT0,GL_SPECULAR,blanc);
  glLightfv(GL_LIGHT0,GL_POSITION,position);
  glMaterialfv(GL_FRONT,GL_AMBIENT,grisFonce);
  glMaterialfv(GL_FRONT,GL_DIFFUSE,grisClair);
  glMaterialfv(GL_FRONT,GL_SPECULAR,blanc);
  glMaterialfv(GL_FRONT,GL_SHININESS,mat_shininess);
  glLightModelfv(GL_LIGHT_MODEL_AMBIENT,lmodel_ambient);
  glEnable(GL_LIGHTING);
  glEnable(GL_LIGHT0);
  glEnable(GL_AUTO_NORMAL);
  glEnable(GL_NORMALIZE);
  glEnable(GL_CULL_FACE);
  glCullFace(GL_FRONT);
  glClearAccum(0.0,0.0,0.0,0.0);
  loaddxdy();
}

void display(void) {
  int i;
  glPushMatrix() ;
  glClear(GL_ACCUM_BUFFER_BIT);
  for (i = 0; i < (ACSIZE); i++) {
    printf("Passe %d\n",i);
    glPushMatrix();
    glRotatef(rx,1.0F,0.0F,0.0F);
    glRotatef(ry,0.0F,1.0F,0.0F);
    glRotatef(rz,0.0F,0.0F,1.0F);
    glTranslatef(dx[i],dy[i],0.0);
    glRotatef(45.0,1.0,1.0,1.0);
    glClear(GL_DEPTH_BUFFER_BIT|GL_COLOR_BUFFER_BIT);
    glutSolidTeapot(1.5);
    glPopMatrix();
    glAccum(GL_ACCUM,1.0/(ACSIZE)); }
  printf("Travail final\n");
  glAccum(GL_RETURN,1.0);
  printf("Termine\n"); 
  glPopMatrix() ;
  glFlush();
  glutSwapBuffers() ;
}

/* Fonction executee lors d'un changement       */
/* de la taille de la fenetre OpenGL            */

void reshape(int x,int y) {
  glViewport(0,0,x,y); 
  glMatrixMode(GL_PROJECTION) ;
  glLoadIdentity() ;
  gluPerspective(15.0F,(float) x/y,1.0,40.0) ;
  glMatrixMode(GL_MODELVIEW) ;
  glLoadIdentity() ;
  gluLookAt(0.0,0.0,20.0,0.0,0.0,0.0,0.0,1.0,0.0);
}

/* Fonction executee lors de l'appui            */
/* d'une touche alphanumerique du clavier       */

void keyboard(unsigned char key,int x,int y) {
  switch (key) {
    /*case 0x0D :
      { static int anim = 1;
        anim = !anim;
        glutIdleFunc(( anim ) ? idle : NULL); }
      break;*/
    case 0x1B :
      exit(0);
      break; }
}

/* Fonction executee lors de l'appui            */
/* d'une touche de curseur ou d'une touche      */
/* page up ou page down                         */

void special(int key,int x,int y) {
  switch(key) {
    case GLUT_KEY_UP :
      rx++;
      glutPostRedisplay() ;
      break;
    case GLUT_KEY_DOWN :
      rx--;
      glutPostRedisplay() ;
      break;
    case GLUT_KEY_LEFT :
      ry++;
      glutPostRedisplay() ;
      break;
    case GLUT_KEY_RIGHT :
      ry--;
      glutPostRedisplay() ;
      break;
    case GLUT_KEY_PAGE_UP :
      rz++;
      glutPostRedisplay() ;
      break;
    case GLUT_KEY_PAGE_DOWN :
      rz--;
      glutPostRedisplay() ;
      break; }
}

int main(int argc,char **argv) {
  glutInit(&argc,argv);
  glutInitDisplayMode(GLUT_RGBA|GLUT_DEPTH|GLUT_DOUBLE|GLUT_ACCUM);
  glutInitWindowSize(300,300); 
  glutInitWindowPosition(50,50); 
  glutCreateWindow("Utilisation du tampon accumulation"); 
  myinit();
  glutReshapeFunc(reshape);
  glutKeyboardFunc(keyboard);
  glutSpecialFunc(special);
  glutDisplayFunc(display);
  glutMainLoop();
  return(0);
}