/* 64 cubes de coté 0.5 places en un cube       */
/* de 4 x 4 x 4 cubes                           */
/* et colores en fonction de leur position      */
/* dans ce cube                                 */
/*                                              */
/* Auteur: Nicolas JANEY                        */
/* nicolas.janey@univ-fcomte.fr                 */
/* Fevrier 2019                                 */

#include <stdio.h>
#include <math.h>

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

/* Variables et constantes globales             */

static const float blanc[]       = { 1.0F,1.0F,1.0F,1.0F };

static int affichage = 1;
static int version = 0;

/* Fonction d'initialisation des parametres     */
/* OpenGL ne changeant pas au cours de la vie   */
/* du programme                                 */

static void init(void) {
  glClearColor(0.25F,0.25F,0.25F,1.0F);
  glLightfv(GL_LIGHT0,GL_DIFFUSE,blanc);
  glEnable(GL_LIGHTING);
  glEnable(GL_LIGHT0);
  glDepthFunc(GL_LESS);
  glEnable(GL_DEPTH_TEST);
  glEnable(GL_NORMALIZE);
}

/* Scene dessinee                               */

static void scene() {
  glPushMatrix();
  for ( int x = -3 ; x <= 3 ; x += 2 )
    for ( int y = -3 ; y <= 3 ; y += 2 )
      for ( int z = -3 ; z <= 3 ; z += 2 ) {
        glPushMatrix();
        glTranslatef((float) x,(float) y,(float) z);
        float couleur[4] = { (x+3)/6.0F,(y+3)/6.0F,(z+3)/6.0F,1.0F };
        glMaterialfv(GL_FRONT,GL_DIFFUSE,couleur);
        glutSolidCube(0.5);
        glPopMatrix(); }
  glPopMatrix();
}

//////////////////////////////////////////////////

static double px = 0.0;
static double py = 0.0;
static double pz = 10.0;

/* Fonction executee lors d'un rafraichissement */
/* de la fenetre de dessin                      */

static void display(void) {
  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  const GLfloat light0_position[] = { 0.0,0.0,10.0,1.0 };
  glPolygonMode(GL_FRONT_AND_BACK,(affichage) ? GL_FILL : GL_LINE);
  glPushMatrix();
  switch (version) {
    case 0 : 
      glLightfv(GL_LIGHT0,GL_POSITION,light0_position);
      gluLookAt(px,py,pz,0.0,0.0,0.0,0.0,1.0,0.0);
      break;
    case 1 : 
      gluLookAt(px,py,pz,0.0,0.0,0.0,0.0,1.0,0.0);
      glLightfv(GL_LIGHT0,GL_POSITION,light0_position);
      break; }
  scene();
  glPopMatrix();
  glFlush();
  glutSwapBuffers();
  int error = glGetError();
  if ( error != GL_NO_ERROR )
    printf("Erreur OpenGL: %d\n",error);
}

/* Fonction executee lors d'un changement       */
/* de la taille de la fenetre OpenGL            */
/* -> Ajustement de la camera de visualisation  */

static void reshape(int tx,int ty) {
  glViewport(0,0,tx,ty); 
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  double ratio =(double) tx/ty;
  if ( ratio >= 1.0 )
    gluPerspective(80.0,ratio,1.0,20.0);
    else
    gluPerspective(80.0/ratio,ratio,1.0,20.0);
  glMatrixMode(GL_MODELVIEW);
  glLoadIdentity();
}

/* Fonction executee lors de la frappe          */
/* d'une touche speciale du clavier             */

static void special(int key,int x,int y) {
  switch ( key ) {
    case GLUT_KEY_UP :
      py += 0.1;
      glutPostRedisplay(); 
      break;
    case GLUT_KEY_DOWN :
      py -= 0.1;
      glutPostRedisplay(); 
      break;
    case GLUT_KEY_LEFT :
      px -= 0.1;
      glutPostRedisplay(); 
      break;
    case GLUT_KEY_RIGHT :
      px += 0.1;
      glutPostRedisplay(); 
      break;
    case GLUT_KEY_PAGE_UP :
      pz -= 0.1;
      glutPostRedisplay(); 
      break;
    case GLUT_KEY_PAGE_DOWN :
      pz += 0.1;
      glutPostRedisplay(); 
      break;
    case GLUT_KEY_F1 :
      px = 0.0;
      py = 0.0;
      pz = 10.0;
      glutPostRedisplay(); 
      break; }
}

//////////////////////////////////////////////////

/* Fonction executee lors de la frappe          */
/* d'une touche du clavier                      */

static void keyboard(unsigned char key,int x,int y) {
  switch ( key ) {
    case 0x20 :
      affichage = (affichage+1)%2;
      glutPostRedisplay(); 
      break;
    case 0x0D :
      version = (version+1)%2;
      glutPostRedisplay(); 
      break;
    case 0x1B :
      exit(0); 
      break; }
}

/* Fonction principale                          */

int main(int argc,char **argv) {
  glutInit(&argc,argv);
  glutInitDisplayMode(GLUT_RGBA|GLUT_DEPTH|GLUT_DOUBLE);
  glutInitWindowSize(360,360); 
  glutInitWindowPosition(50,50); 
  glutCreateWindow("64 cubes"); 
  init();
  glutKeyboardFunc(keyboard);
  glutSpecialFunc(special);
  glutReshapeFunc(reshape);
  glutDisplayFunc(display);
  glutMainLoop();
  return(0);
}