/* Un programme OpenGL de deplacement           */
/* d'une camera au sein d'une scene animee      */
/*                                              */
/* Auteur: Nicolas JANEY                        */
/* nicolas.janey@univ-fcomte.fr                 */
/* Octobre 2009                                 */

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

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

/* Variables globales                           */

static int l = 1;

static float px = 0.0F;
static float py = 0.5F;
static float pz = 0.0F;
static float angle = 0.0F;
static float ouv = 60.0F;
static int anim = 0;
static float x[100];
static float z[100];
static float ryl = 0.0F;

/* Fonction executee lors d'un changement       */
/* de la taille de la fenetre OpenGL            */
/* Configuration d'une camera de visualisation  */
/* en projection en perspective                 */

void reshape(int tx,int ty) {
  /* Configuration du viewport d'affichage      */
  glViewport(0,0,tx,ty);
  /* Choix et configuration de la camera        */
  /* de visualisation                           */
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  gluPerspective(ouv,(double) tx/ty,0.01,100.0);
  glMatrixMode(GL_MODELVIEW);
  glLoadIdentity();
}

/* Scene dessinee                               */

void cylindre(double h,double r,int n,int m) {
  glPushMatrix();
  glRotatef(90.0F,1.0F,0.0F,0.0F);
  glTranslatef(0.0F,0.0F,-h/2);
  GLUquadricObj *qobj = gluNewQuadric();
  gluQuadricDrawStyle(qobj,GLU_FILL);
  gluCylinder(qobj,r,r,h,n,m);
  gluDeleteQuadric(qobj);  
  glPopMatrix();
}

void scene(int l) {
  int i;
  const GLfloat l_pos[] = { 5.0F,1.0F,0.0F,1.0F };
  const GLfloat blanc[4] = { 1.0F,1.0F,1.0F,1.0F };
  const GLfloat c1[4] = { 1.0F,1.0F,1.0F,1.0F };
  const GLfloat c2[4] = { 0.1F,0.7F,0.6F,1.0F };
  const GLfloat c3[4] = { 1.0F,1.0F,0.0F,1.0F };
  if ( l )
    glEnable(GL_LIGHTING);
    else
    glDisable(GL_LIGHTING);
  glLightfv(GL_LIGHT1,GL_DIFFUSE,blanc);
  glEnable(GL_LIGHT0);
  glEnable(GL_DEPTH_TEST);
  glEnable(GL_NORMALIZE);
  glPushMatrix();
  glRotatef(ryl,0.0F,1.0F,0.0F);
  glLightfv(GL_LIGHT0,GL_POSITION,l_pos);
  glPopMatrix();
  glPushMatrix();
  glRotatef(ryl,0.0F,1.0F,0.0F);
  glTranslatef(5.0F,1.0F,0.0F);
  glEnable(GL_LIGHT1);
  glMaterialfv(GL_FRONT,GL_DIFFUSE,blanc);
  glutSolidSphere(0.1,36,36);
  glDisable(GL_LIGHT1);
  glPopMatrix();
  glPushMatrix();
  glNormal3f(0.0F,1.0F,0.0F);
  glMaterialfv(GL_FRONT,GL_DIFFUSE,c1);
  glColor4fv(c1);
  glBegin(GL_QUADS);
  for ( i = 0 ; i < 20 ; i++ ) {
    for ( int j = 0 ; j < 20 ; j++ ) {
      if ( (i+j)%2 == 1 ) {
        glVertex3f(i-10.0F,0.0F,j-10.0F);
        glVertex3f(i-9.0F,0.0F,j-10.0F);
        glVertex3f(i-9.0F,0.0F,j-9.0F);
        glVertex3f(i-10.0F,0.0F,j-9.0F); } } }
  glEnd();
  glMaterialfv(GL_FRONT,GL_DIFFUSE,c2);
  glColor4fv(c2);
  glBegin(GL_QUADS);
  for ( i = 0 ; i < 20 ; i++ ) {
    for ( int j = 0 ; j < 20 ; j++ ) {
      if ( (i+j)%2 == 0 ) {
        glVertex3f(i-10.0F,0.0F,j-10.0F);
        glVertex3f(i-9.0F,0.0F,j-10.0F);
        glVertex3f(i-9.0F,0.0F,j-9.0F);
        glVertex3f(i-10.0F,0.0F,j-9.0F); } } }
  glEnd();
  glMaterialfv(GL_FRONT,GL_DIFFUSE,c3);
  glColor4fv(c3);
  for ( i = 0 ; i < 100 ; i++ ) {
    glPushMatrix();
    glTranslatef(x[i],1.0F,z[i]);
    cylindre(2.0,0.05,20,20);
    glPopMatrix(); }
  glPopMatrix();
}

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

void display(void) {
  glClearColor(0.6F,0.6F,0.6F,1.0F) ;
  glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT) ;
  glPushMatrix();
  gluLookAt(px,py,pz,
            px+sin(angle),py,pz+cos(angle),
            0.0,1.0,0.0);
  /* Affichage de la scene                      */
  scene(1);
  glPopMatrix();
  glFlush();
  glutSwapBuffers();
  int error = glGetError();
  if ( error != GL_NO_ERROR )
    printf("Attention, erreur OpenGL %d\n",error);
}

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

int positionAcceptable(float px,float pz) {
  for ( int i = 0 ; i < 100 ; i++ ) {
    float dx = px-x[i];
    float dz = pz-z[i];
    float d = sqrt(dx*dx+dz*dz);
    if ( d < 0.06F )
      return(0); }
  return(1);
}

void special(int key,int x,int y) {
  switch ( key ) {
    case GLUT_KEY_UP      : { float npx = px + 0.1F*sin(angle);
                              float npz = pz + 0.1F*cos(angle);
                              if ( positionAcceptable(npx,npz) ) {
                                px = npx;
                                pz = npz;
                                glutPostRedisplay(); } }
                            break;
    case GLUT_KEY_DOWN    : { float npx = px - 0.1F*sin(angle);
                              float npz = pz - 0.1F*cos(angle);
                              if ( positionAcceptable(npx,npz) ) {
                                px = npx;
                                pz = npz;
                                glutPostRedisplay(); } }
                            break;
    case GLUT_KEY_RIGHT   : angle -= 0.03F;
                            glutPostRedisplay();
                            break;
    case GLUT_KEY_LEFT    : angle += 0.03F;
                            glutPostRedisplay();
                            break; }
}

/* Fonction executee lorsqu'aucun evenement     */
/* n'est en attente de gestion                  */

void idle(void) {
  ryl += 1.0F;
  glutPostRedisplay();
}

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

void keyboard(unsigned char key,int x,int y) {
  switch ( key ) {
    case 0x0D : { anim = !anim;
                  glutIdleFunc((anim) ? idle : NULL); }
                break;
    case 0x20 : l = !l ;
                glutPostRedisplay();
                break;
    case 0x1B : exit(0); }
}

/* Fonction principale                          */

int main(int argc,char **argv) {
  srand(0);
  for ( int i = 0 ; i < 100 ; i++ ) {
    x[i] = -10.0F+((float) (rand()%1000)/50.0F); 
    z[i] = -10.0F+((float) (rand()%1000)/50.0F); }
  glutInit(&argc,argv);
  glutInitDisplayMode(GLUT_RGBA|GLUT_DOUBLE|GLUT_DEPTH);
  glutInitWindowSize(450,200); 
  glutInitWindowPosition(50,50); 
  glutCreateWindow("Deplacement de camera et scene animee");
  glutReshapeFunc(reshape);
  glutKeyboardFunc(keyboard);
  glutSpecialFunc(special);
  glutDisplayFunc(display);
  glutMainLoop();
  return(0);
}