glColor and GL_LINES

[bingofuel]

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?



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

this very basic code doesn't work



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 );

}

[jcox23]

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?

[bingofuel]

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


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();
}

[jcox23]

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?

[mpi]

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

Mads

[bingofuel]

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.

[ralfi102]

if you have


glEnable(GL_LIGHTING);

then you should have


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

otherwise glColor3f() has no meaning at all..