Seems like glPopMatrix() doesn't reset the transformationmatrix

Question

I'm trying to make the solar system in OpenGL. Everytime I add a planet I need to pop the transformationmatrix so I can start over with the next one. This is working for only 2 planets. I am able to add a first planet (earth) and let is spin around the sun. Then I use glPopMatrix() and add a second planet spinning around the sun, this again works fine. But when I try to add a 3rd planet and do the exact same thing (pop the stack first and make it spin around the sun), it looks like the transformationMatrix isn't being reseted and the 3rd planet spins around the 2nd one like the 1st and 2nd planet spin around the sun.

Here is the code of my paintGL():

    void PlanetsView::paintGL ()
{
    this->dayOfYear = (this->dayOfYear+1);
    this->hourOfDay = (this->hourOfDay+1) % 24;

    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    glLoadIdentity();

    // store current matrix
    glMatrixMode( GL_MODELVIEW );

    gluLookAt(camPosx ,camPosy ,camPosz,
              camViewx,camViewy,camViewz,
              camUpx, camUpy, camUpz );


    //Draw Axes
    glDisable( GL_LIGHTING );
    glBegin(GL_LINES);
    glColor3f(1.0, 0.0, 0.0);
    glVertex3f(0.0, 0.0, 0.0);
    glVertex3f(10.0, 0.0, 0.0);
    glColor3f(0.0, 1.0, 0.0);
    glVertex3f(0.0, 0.0, 0.0);
    glVertex3f(0.0, 10.0, 0.0);
    glColor3f(0.0, 0.0, 1.0);
    glVertex3f(0.0, 0.0, 0.0);
    glVertex3f(0.0, 0.0, 10.0);
    glEnd();
    glEnable( GL_LIGHTING );

    glPushMatrix();

    // rotate the plane of the elliptic
    glRotated ( 5.0, 1.0, 0.0, 0.0 );

    // draw the sun
    GLfloat diff [] = { 0.7f , 0.5f , 0.0f };
    glMaterialfv ( GL_FRONT, GL_DIFFUSE, diff );

    //glutSolidSphere( 3.0, 25, 25 );
    solidSphere(3.0, 25, 25);

    // rotate the earth around the sun
    glRotated( (GLdouble)(360.0 * dayOfYear /365.0), 0.0, 1.0, 0.0 );
    glTranslated ( 4.0, 0.0, 0.0 );
    // rotate the earth around its axis
    glRotated( (GLdouble)(360.0 * hourOfDay/24.0), 0.0, 1.0, 0.0 );

    // draw the earth
    GLfloat diff2 [] = { 0.2f , 0.2f , 0.8f };
    glMaterialfv ( GL_FRONT, GL_DIFFUSE, diff2 );
    solidSphere(0.3, 25, 25);

    glPopMatrix();

   // rotate the new planet around the sun
    glRotated( (GLdouble)(360.0 * dayOfYear /150.0), 0.0, 1.0, 0.0 );
    glTranslated ( 6.0, 0.0, 0.0 );

    // rotate the new planet around its axis
    glRotated( (GLdouble)(360.0 * hourOfDay/36.0), 0.0, 1.0, 0.0 );


    // draw the new planet
    GLfloat diff3 [] = { 1.0f , 0.0f , 0.0f }; // red color
    glMaterialfv ( GL_FRONT, GL_DIFFUSE, diff3 );
    solidSphere(0.4, 25, 25);

    glPopMatrix();  // looks like this pop doesn't do anything


    /* From here, when adding a 3rd planet, it fails */
    // rotate a 3rd planet around the sun
    glRotated( (GLdouble)(360.0 * dayOfYear /800.0), 0.0, 1.0, 0.0 );
    glTranslated ( 6.0, 0.0, 0.0 );

    // rotate a 3rd planet around its axis
    glRotated( (GLdouble)(360.0 * hourOfDay/12.0), 0.0, 1.0, 0.0 );

    // draw the 3rd planet
    GLfloat diff4 [] = { 1.0f , 1.0f , 0.0f }; // red color
    glMaterialfv ( GL_FRONT, GL_DIFFUSE, diff4 );
    solidSphere(0.3, 25, 25);

    glPopMatrix();

}

And here is the code of solidSphere:

    void solidSphere(GLdouble radius, GLint slices, GLint stacks)
{
    glBegin(GL_LINE_LOOP);
    GLUquadricObj* quadric = gluNewQuadric();

    gluQuadricDrawStyle(quadric, GLU_FILL);
    gluSphere(quadric, radius, slices, stacks);

    gluDeleteQuadric(quadric);
    glEnd();

}

Answer 1

glPopMatrix();  // looks like this pop doesn't do anything

Correct, this does not do anything (meaningful), you are underflowing the matrix stack.

You already popped the last thing off the stack a few lines prior to that.

If your intention was to have the second call to glPopMatrix () restore the matrix as it existed after calling glEnable( GL_LIGHTING ), then you need to add a call to glPushMatrix () immediately after your first glPopMatrix (). And you need to repeat that process one more time so that your third call to glPopMatrix () does not also underflow the stack.

I get the impression you are not quite clear how stacks work.