Here I am trying to draw a cube with three faces.One face is red, one green and one blue.
Then I rotate the cube in a way that I should see half of the red face and half of the green face, of 45 degrees around the y axis.I should see a half red and half green cube, but I only see the red face, that's the code:

Code :
#import <OpenGL/OpenGL.h>
#import <GLUT/GLUT.h>
 
 
int width=500, height=500, depth=500;
 
 
void init()
{
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glEnable(GL_DEPTH_TEST);
    glViewport(0, 0, width, height);
    glOrtho(0, width, height, 0, 0, depth);
}
 
 
void display()
{
    glClearColor(0.9, 0.9, 0.9, 0);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glBegin(GL_QUADS);
    gluLookAt(250, 250, 0, -250, 250, 250, 0, 1, 0);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
    glRotatef(45, 0, 1, 0);
 
    // First face
    glColor4f(1, 0, 0, 0);
    glVertex3i(100, 100,0);
    glVertex3i(300, 100,0);
    glVertex3i(300, 300,0);
    glVertex3i(100, 300,0);
 
    // Second face
    glColor4f(0, 1, 0, 0);
    glVertex3i(300,100,0);
    glVertex3i(300,300,0);
    glVertex3i(300,100,300);
    glVertex3i(300,100,300);
 
    // Third face
    glColor4f(0, 0, 1, 0);
    glVertex3i(100, 100,300);
    glVertex3i(300, 100,300);
    glVertex3i(300, 300,300);
    glVertex3i(100, 300,300);
 
    glEnd();
    glFlush();
}
 
 
int main(int argc, char * argv[])
{
    glutInit(&argc, argv);
    glutInitWindowPosition(100, 100);
    glutInitWindowSize(width, height);
    glutCreateWindow("Test");
    glutDisplayFunc(display);
    init();
    glutMainLoop();
    return 0;
}

PS: Code outdated because my university is outdated