r3n

    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    glPushMatrix();
    glLoadIdentity();

    // ... do some translation ...

    drawCube();

    glPopMatrix();

    glPushMatrix();
    glLoadIdentity();

    // ... do some translation ...

    glBegin(GL_QUADS);

    // Use a dark gray background and set transparency.
    glColor4f(1.0, 1.0, 1.0, .5);

    glVertex3f(-1.0, +1.0, 0.0); // top left
    glVertex3f(-1.0, -1.0, 0.0); // bottom left
    glVertex3f(+1.0, -1.0, 0.0); // bottom right
    glVertex3f(+1.0, +1.0, 0.0); // top right
    glEnd();

    glPopMatrix();

    // ... swap the buffers ...