/* Sphere modelisee par facettes                */
/*                                              */
/* Auteur: Nicolas JANEY                        */
/* nicolas.janey@univ-fcomte.fr                 */
/* Septembre 2009                               */

#include <stdlib.h>
#include <stdio.h>
#include <math.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 rayon = 2.0F;
static int n = 36;
static int m = 36;
static float rx = 0.0F;
static float ry = 0.0F;
static float rz = 0.0F;
static const float blanc[] = { 1.0F,1.0F,1.0F,1.0F };
static const float gris[] = { 0.7F,0.7F,0.7F,1.0F };
static const float jaune[] = { 1.0F,1.0F,0.0F,1.0F };
static const float rouge[] = { 1.0F,0.0F,0.0F,1.0F };
static const float vert[] = { 0.0F,1.0F,0.0F,1.0F };
static const float bleu[] = { 0.0F,0.0F,1.0F,1.0F };

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

void init(void) {
  const GLfloat shininess[] = { 50.0 };
  glMaterialfv(GL_FRONT,GL_SPECULAR,blanc);
  glMaterialfv(GL_FRONT,GL_SHININESS,shininess);
  glLightfv(GL_LIGHT0,GL_DIFFUSE,rouge);
  glLightfv(GL_LIGHT1,GL_DIFFUSE,jaune);
  glLightfv(GL_LIGHT2,GL_DIFFUSE,bleu);
  glEnable(GL_LIGHTING);
  glEnable(GL_LIGHT0);
  glEnable(GL_LIGHT1);
  glEnable(GL_LIGHT2);
  glDepthFunc(GL_LESS);
  glEnable(GL_DEPTH_TEST);
  glEnable(GL_NORMALIZE);
  glEnable(GL_AUTO_NORMAL);
}

/* Scene dessinee                               */

#ifndef M_PI
#define M_PI 3.14159265358979323846264338327950288
#endif

void solidSphere(float rayon,int nlat,int nlon) {
  for ( int i = 0 ; i < nlat ; i++ ) {
    float a1 = -M_PI/2.0F + i*M_PI/nlat ;
    float a2 = a1 + M_PI/nlat ;
    float cs1 = cos(a1);
    float cs2 = cos(a2);
    float sn1 = sin(a1);
    float sn2 = sin(a2);
    glBegin(GL_QUAD_STRIP);
    for ( int j = 0 ; j <= nlon ; j++ ) {
      float a = j*2*M_PI/nlon;
      float cs = cos(a);
      float sn = sin(a);
      float x1 = cs1*cs;
      float z1 = cs1*sn;
      float x2 = cs2*cs;
      float z2 = cs2*sn;
      glNormal3f(x1,sn1,z1);
      glVertex3f(rayon*x1,rayon*sn1,rayon*z1);
      glNormal3f(x2,sn2,z2);
      glVertex3f(rayon*x2,rayon*sn2,rayon*z2); }
    glEnd(); }
}

void scene() {
  glPushMatrix();
  solidSphere(rayon,n,m);
  glPopMatrix();
}

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

void display(void) {
  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  const GLfloat light0_position[] = { 1.0,1.0,1.0,0.0 };
  const GLfloat light1_position[] = { -1.0,1.0,1.0,0.0 };
  const GLfloat light2_position[] = { 1.0,-1.0,1.0,0.0 };
  glLightfv(GL_LIGHT0,GL_POSITION,light0_position);
  glLightfv(GL_LIGHT1,GL_POSITION,light1_position);
  glLightfv(GL_LIGHT2,GL_POSITION,light2_position);
  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);
  scene();
  glPopMatrix();
  glFlush();
  glutSwapBuffers();
  int error = glGetError();
  if ( error != GL_NO_ERROR )
    printf("Erreur OpenGL\n",error);
}

/* Fonction executee lorsqu'aucun evenement     */
/* n'est en file d'attente                      */

void idle(void) {
  rx += 0.4256F + (rand()%1000)/1000.0F ;
  ry += 0.6117F ;
  rz += 0.4174F ;
  glutPostRedisplay() ;
}

/* 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(25.0F,(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 'l' :
      { static int lumiere = 0;
        lumiere = !lumiere;
        if ( lumiere ) {
          glLightfv(GL_LIGHT0,GL_DIFFUSE,gris);
          glLightfv(GL_LIGHT1,GL_DIFFUSE,gris);
          glLightfv(GL_LIGHT2,GL_DIFFUSE,gris);
          glEnable(GL_CULL_FACE); }
          else {
          glLightfv(GL_LIGHT0,GL_DIFFUSE,rouge);
          glLightfv(GL_LIGHT1,GL_DIFFUSE,jaune);
          glLightfv(GL_LIGHT2,GL_DIFFUSE,bleu);
          glDisable(GL_CULL_FACE); } }
      glutPostRedisplay();
      break;
    case 'c' :
      { static int culling = 0;
        culling = !culling;
        if ( culling )
          glEnable(GL_CULL_FACE);
          else
          glDisable(GL_CULL_FACE); }
      glutPostRedisplay();
      break;
    case 'f' :
      { static int face = 1;
        face = !face;
        glPolygonMode(GL_FRONT_AND_BACK,( face ) ? GL_FILL : GL_LINE); }
      glutPostRedisplay();
      break;
    case 'n'  :
      n--;
      if ( n < 2 )
        n = 2;
      glutPostRedisplay();
      break;
    case 'N'  :
      n++;
      glutPostRedisplay();
      break;
    case 'm'  :
      m--;
      if ( m < 3 )
        m = 3;
      glutPostRedisplay();
      break;
    case 'M'  :
      m++;
      glutPostRedisplay();
      break;
    case '+'  :
      rayon += 0.1F;
      glutPostRedisplay();
      break;
    case '-'  :
      rayon -= 0.1F;
      if ( rayon < 0.1F )
        rayon = 0.1F;
      glutPostRedisplay();
      break;
    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; }
}

/* Fonction principale                          */

int main(int argc,char **argv) {
  glutInit(&argc,argv);
  glutInitDisplayMode(GLUT_RGBA|GLUT_DEPTH|GLUT_DOUBLE);
  glutInitWindowSize(300,300); 
  glutInitWindowPosition(50,50); 
  glutCreateWindow("Une sphère modélisée par facettes"); 
  init();
  glutKeyboardFunc(keyboard);
  glutSpecialFunc(special);
  glutReshapeFunc(reshape);
  glutIdleFunc(idle);
  glutDisplayFunc(display);
  glutMainLoop();
  return(0);
}