Непонятки с освещением

void simple_gl_widget::initializeGL()
{
    qglClearColor(Qt::black);
    glEnable(GL_DEPTH_TEST);
    glEnable(GL_COLOR_MATERIAL);
    glShadeModel(GL_SMOOTH);
 
    GLfloat amb_light[] = {0.5, 0.5, 0.5, 1};
    glLightfv(GL_LIGHT0, GL_AMBIENT, amb_light);
    GLfloat c0[] = {1, 1, 1, 1};
    glLightfv(GL_LIGHT0, GL_SPECULAR, c0);
    glLightfv(GL_LIGHT0, GL_DIFFUSE, c0);
 
    glEnable(GL_LIGHT0);
    glEnable(GL_LIGHTING);
}
 
 
void simple_gl_widget::draw_axe(double length, const QString& lbl)
{
    GLfloat amb_mat[] = {0.3, 0.3, 0.8, 1};
    glMaterialfv(GL_FRONT_AND_BACK, GL_AMBIENT, amb_mat);
 
    GLfloat mat[] = {0.5, 0.5, 1, 1};
    glMaterialfv(GL_FRONT_AND_BACK, GL_DIFFUSE, mat);
    glColor3f(0.3, 0.3, 0.8);//REMEMBER: you must change color simultaneously with material!!
    glPushMatrix();
    glBegin(GL_LINES);
    glVertex3f(0,0,0);
    glVertex3f(0,0,length);
    glEnd();
 
    //drawing cone on the end of axe
    glTranslated(0,0,length - 0.7);
    glutWireCone(0.2, 0.7, 96, 96);
    this->renderText(1.2,1.2,-1.2, lbl);
    glPopMatrix();
}
 
 
void simple_gl_widget::draw_axes(double max_x, double max_y, double max_z)
{
    draw_axe(max_z, "Z");
 
    glPushMatrix();
    glRotated(90, 0, 1, 0);
    draw_axe(max_x, "X");
 
    glRotated(-90, 1, 0, 0);
    draw_axe(max_y, "Y");
    glPopMatrix();
}
 
void simple_gl_widget::paintGL()
{
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
 
    //scale world if necessary
    this->scale_world_for_next_points(12);
 
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
 
    glMultMatrixf(Transform.M);
 
    draw_axes( maximum(max_x, fabs(min_x))+5, maximum(fabs(min_y), max_y)+5, maximum(max_z, fabs(min_z))+5);
 
    //redraw existed lines;
    this->redraw_ex_points();
 
    if ((!this->mouse_pressed) && this->draw_timer)
        draw_next_point();
 
    this->draw_last_point();
}
 
void simple_gl_widget::redraw_ex_points()
{
        QColor t = i->trajectory_color;
        
        GLfloat amb_mat[] = {t.redF()-0.2, t.greenF()-0.2, t.blueF()-0.2};
        glMaterialfv(GL_FRONT_AND_BACK, GL_AMBIENT, amb_mat);
        GLfloat mat[] = {t.redF(), t.greenF(), t.blueF()};
        glMaterialfv(GL_FRONT_AND_BACK, GL_SPECULAR, mat);
        glMaterialfv(GL_FRONT_AND_BACK, GL_DIFFUSE, mat);
        
        glColor3f(t.redF() , t.greenF(), t.blueF());
        glBegin(GL_LINE_STRIP);
        {
            for (vector<point_3d>::const_iterator j = i->points.begin(); j != i->points.end(); j++ )
                glVertex3f(j->x, j->y, j->z);
        }
}