glColor and GL_LINES

hi!.
I'm using Qt 4.6 in GNU/Linux. i'm working with QGLWidget with kind of easiness but i've a problem when i want to change the color of the Lines.
I've tried all the combinations that i could think.
i've put the glColor after and befor de glBegin, use the qglColor, and glColor3f (and others glColors functions). But always it's a random color between blue and green (never red (i don't know why)).
What am i missing?

Code:

---

glBegin(GL_LINES);
    glColor3f(1.0f,0.0,0.0);
     glVertex2f(50,1);
     glVertex2f(120,1);
  glEnd()
;

---

this very basic code doesn't work

Code:

---

void Plot::paintGL()
{
    glBegin(GL_LINES);
    glColor3f(1.0f,0.0,0.0);
     glVertex2f(50,1);
 
     glVertex2f(120,1);
    glEnd();
}
 
void Plot::initializeGL()
{
  // Also i've tried a lot of combinations here. GL_FLAT and others.
    glClearColor(1.0, 1.0 , 1.0, 0.0);
    glLoadIdentity();
    glTranslatef(0,0.0,0);
    glDisable(GL_TEXTURE_2D);
    glDisable(GL_LIGHTING);
    glShadeModel(GL_SMOOTH);
 
}
 
 
void Plot::resizeGL(int w, int h)
{
    glViewport( 0, 0, (GLint)w, (GLint)h );
    glMatrixMode( GL_PROJECTION );
    glLoadIdentity();
 
    glOrtho( 0, 800, yMin, yMax, -5.0, 1.0 );
    glMatrixMode( GL_MODELVIEW );
 
}

---

I dont see any:
glClear(GL_CLEAR_COLOR_BUFFER_BIT | GL _DEPTH_BUFFER_BIT)
at the beginning of your paintGL() routine...

is that on purpose?

Quote:

---

I dont see any:
glClear(GL_CLEAR_COLOR_BUFFER_BIT | GL _DEPTH_BUFFER_BIT)
at the beginning of your paintGL() routine...

is that on purpose?

---

yes, is on porpouse beacouse i'm writing an application that don't erase the screen every frame.
But is the same thing with the color clearing the buffers or not :s

Code:

---

void Plot::paintGL()
{
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glBegin(GL_LINES);
    glColor3f(1.0f,0.0,0.0);
     glVertex2f(50,1);
 
     glVertex2f(120,1);
    glEnd();
}

---

I just copied/pasted your code into the hellogl example....and it's working as intended... (line is red)
so the code is probably ok...

are the Qt OpenGL examples working alright?

Could be a driver issue. What platform are you running on? What OpenGL driver do you use?

Mads

i'm using a x86 GNU/Linux with an ATI raden 9550 using the open-source drivers ( xf86-video-ati 6.12.4-3 )
Mesa Version mesa 7.7-1

i've tried in a machine with xp and works fine.

if you have

Code:

---

glEnable(GL_LIGHTING);

---

then you should have

Code:

---

glColorMaterial ( GL_FRONT_AND_BACK, GL_AMBIENT_AND_DIFFUSE );
glEnable ( GL_COLOR_MATERIAL );

---

otherwise glColor3f() has no meaning at all..