Opengl camera and render problems - c++

Question

I'm acutally trying open gl and have some questions:
I actually have this code:
#include <freeglut.h>
#include <glut.h>
#include <stdio.h>
using namespace std;
char presse;
int anglex=-45, angley=45, x, y, xold, yold;
/* Prototype des fonctions (function prototypes) */
void affichage();
void clavier(unsigned char touche, int x, int y);
void reshape(int x, int y);
void idle();
void mouse(int bouton, int etat, int x, int y);
void mousemotion(int x, int y);
const GLfloat light_ambient[] = { 0.0f, 0.0f, 0.0f, 1.0f };
const GLfloat light_diffuse[] = { 1.0f, 1.0f, 1.0f, 1.0f };
const GLfloat light_specular[] = { 1.0f, 1.0f, 1.0f, 1.0f };
const GLfloat light_position[] = { 1, 2, 1, 1 };
const GLfloat mat_ambient[] = { 0.7f, 0.7f, 0.7f, 1.0f };
const GLfloat mat_diffuse[] = { 0.8f, 0.8f, 0.8f, 1.0f };
const GLfloat mat_specular[] = { 1.0f, 1.0f, 1.0f, 1.0f };
const GLfloat high_shininess[] = { 100.0f };
int main(int argc, char **argv)
{
/* initialisation de glut et creation
de la fenetre (glut initialization and window creation) */
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);
glutInitWindowPosition(200, 200);
glutInitWindowSize(1000, 1000);
glutCreateWindow("cube");
/* Initialisation d'OpenGL (OpenGL initialisation) */
glClearColor(0.0, 0.0, 0.0, 0.0);
glColor3f(1.0, 1.0, 1.0);
glPointSize(2.0);
glEnable(GL_DEPTH_TEST); // Active le test de profondeur
(activate depth testing)
glEnable(GL_LIGHTING); // Active l'éclairage
(activate lighting)
glEnable(GL_LIGHT0); // Allume la lumière n°1
(turn on light no. 1)
glEnable(GL_NORMALIZE);
glEnable(GL_COLOR_MATERIAL);
glLightfv(GL_LIGHT0, GL_AMBIENT, light_ambient);
glLightfv(GL_LIGHT0, GL_DIFFUSE, light_diffuse);
glLightfv(GL_LIGHT0, GL_SPECULAR, light_specular);
glLightfv(GL_LIGHT0, GL_POSITION, light_position);
glMaterialfv(GL_FRONT, GL_AMBIENT, mat_ambient);
glMaterialfv(GL_FRONT, GL_DIFFUSE, mat_diffuse);
glMaterialfv(GL_FRONT, GL_SPECULAR, mat_specular);
glMaterialfv(GL_FRONT, GL_SHININESS, high_shininess);
/* enregistrement des fonctions de rappel (register callbacks) */
glutDisplayFunc(affichage);
glutKeyboardFunc(clavier);
glutReshapeFunc(reshape);
glutMouseFunc(mouse);
glutMotionFunc(mousemotion);
/* Entree dans la boucle principale glut (entry of the main glut loop) */
glutMainLoop();
return 0;
}
double a = 0;
int LightPos[4] = { -1, 4, -1, 1 };
int MatSpec[4] = { 1, 1, 1, 1 };
void affichage()
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glShadeModel(GL_SMOOTH);
glMatrixMode(GL_MODELVIEW);
glViewport(0, 0, 1000, 1000);
a = +1;
glLoadIdentity();
glRotatef(angley, 1.0, 0.0, 0.0);
glRotatef(anglex, 0.0, 1.0, 0.0);
for (int k = 0; k < 5; k++){
if (k == 0){
glBegin(GL_LINES);
glColor3f(1.0, 1.0, 1.0);
glVertex3f(0, 0, 0);
glVertex3f(1, 0, 0);
glEnd();
}
else {
if (k > 0){
glBegin(GL_LINES);
glColor3f(1.0, 0.0, 0);
glVertex3f(0.5, 0, 0);
glVertex3f(0.5, 0, 0.5);
glEnd();
}
glBegin(GL_LINES);
glColor3f(1.0, 0.0, 0);
glVertex3f(k, 0, 0);
glVertex3f(k, 0, 0.5);
glEnd();
}
}
for (int k = 0; k < 5; k++){
if (k == 0){
glBegin(GL_LINES);
glColor3f(1.0, 0.0, 1.0);
glVertex3f(0, 0, 0);
glVertex3f(0, 5, 0);
glEnd();
}
else {
if (k >0){
GLfloat n = k / 2;
glBegin(GL_LINES);
glColor3f(0.0, 1.0, 0);
glVertex3f(0, 0.5, 0);
glVertex3f(0.5, 0.5, 0);
glEnd();
}
glBegin(GL_LINES);
glColor3f(0.0, 1.0, 0);
glVertex3f(0, k, 0);
glVertex3f(0.5, k, 0);
glEnd();
}
}
for (int k = 0; k < 5; k++){
if (k == 0){
glBegin(GL_LINES);
glColor3f(1.0, 0.6, 1.0);
glVertex3f(0, 0, 0);
glVertex3f(0, 0, 5);
glEnd();
}
else {
if (k >0){
GLfloat n = k / 2;
glBegin(GL_LINES);
glColor3f(0.0, 0.0, 1.0);
glVertex3f(0, 0, 0.5);
glVertex3f(0, 0.5, 0.5);
glEnd();
}
glBegin(GL_LINES);
glColor3f(0.0, 0.0, 10);
glVertex3f(0, 0, k);
glVertex3f(0, 0.5, k);
glEnd();
}
}
// Par terre scene
(ground scene)
glBegin(GL_QUADS);
glColor3f(1.0, 1.0, 1.0);
glVertex3d(0,-0.1,0);
glVertex3d(5, -0.1, 0);
glVertex3d(5, -0.1, 5);
glVertex3d(0, -0.1, 5);
glEnd();
glFlush();
glutSwapBuffers();
}
void clavier(unsigned char touche, int x, int y)
{
switch (touche)
{
case 'o': /* eteindre la lumiere (turn off the light) */
glDisable(GL_LIGHT0);
glutPostRedisplay();
//std::cout << "lumiere eteinte";
break;
case 'a': /* eteindre la lumiere (turn off the light) */
glEnable(GL_LIGHT0);
glutPostRedisplay();
break;
case 'p': /* affichage du carre plein (normal fill mode, interior of the polygon is filled) */
glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
glutPostRedisplay();
break;
case 'f': /* affichage en mode fil de fer (draw polygon edges as lines) */
glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
glutPostRedisplay();
break;
case 's': /* Affichage en mode sommets seuls (draw polygon vertices as points) */
glPolygonMode(GL_FRONT_AND_BACK, GL_POINT);
glutPostRedisplay();
break;
case 'd':
glEnable(GL_DEPTH_TEST);
glutPostRedisplay();
break;
case 'D':
glDisable(GL_DEPTH_TEST);
glutPostRedisplay();
break;
case 'q': /*la touche 'q' permet de quitter le programme (the key 'q' exits the program) */
exit(0);
}
}
void reshape(int x, int y)
{
if (x<y)
glViewport(0, (y - x) / 2, x, x);
else
glViewport((x - y) / 2, 0, y, y);
}
void mouse(int button, int state, int x, int y)
{
/* si on appuie sur le bouton gauche (if you press the left button) */
if (button == GLUT_LEFT_BUTTON && state == GLUT_DOWN)
{
presse = 1; /* le booleen presse passe a 1 (vrai) (the boolean presse is set to 1 (true)) */
xold = x; /* on sauvegarde la position de la souris (save the position of the mouse) */
yold = y;
}
/* si on relache le bouton gauche (if you release the left button) */
if (button == GLUT_LEFT_BUTTON && state == GLUT_UP)
presse = 0; /* le booleen presse passe a 0 (faux) (the boolean presse is set to 0 (false)) */
}
void mousemotion(int x, int y)
{
if (presse) /* si le bouton gauche est presse (if the left button is pressed) */
{
/* on modifie les angles de rotation de l'objet
en fonction de la position actuelle de la souris et de la derniere
position sauvegardee (modify the rotation angles of the object
depending on the current position of the mouse and the last
saved position) */
anglex = anglex + (x - xold);
angley = angley + (y - yold);
glutPostRedisplay();
}
xold = x;
yold = y;
}
But I can't manage the scene to just draw the x,y and z axis to it's full extend. The rendered object are "cut" in the screen. How can I first draw them entirely and then move the camera backwards? I happily already managed the move the camera a bit etc.. but it's still freaking complicated...
Any advice is welcome.

Answer 1

You are not setting up any specific projection matrix, so you will get the default of an identity matrix. This means that the viewing volume will range from -1 to 1 along all three axis. Hence, objects are cut if they reach outside of this volume.