OpenGL and QPainter

[wererabit]

Hi,

I am trying to add openGL into my program. What I want is to have a gradient background on the back (using QPainter) and say a triangle (openGL) in the front. My problem is that the 2D painting always lies on top of the OpenGL painting. Could anyone show me how I can fix this?

I included the code below in case anyone want to have a look. So what I currently have is only the gradient background and no triangles since they are hidden behind the background.

Thanks a tons

void GLWidget::paintEvent(QPaintEvent *event)
{
	QPainter painter(this);
	painter.setPen(Qt::NoPen);
	painter.setBrush(gradient);
	painter.drawRect(rect());       //paint the background with linear gradient
	painter.end();
 
    makeCurrent();
 
    glMatrixMode(GL_MODELVIEW);
    glPushMatrix();
    glShadeModel(GL_SMOOTH);
    glEnable(GL_DEPTH_TEST);
    glEnable(GL_CULL_FACE);
    glEnable(GL_LIGHTING);
    glEnable(GL_LIGHT0);
    glEnable(GL_MULTISAMPLE);
    static GLfloat lightPosition[4] = { 0.5, 5.0, 7.0, 1.0 };
    glLightfv(GL_LIGHT0, GL_POSITION, lightPosition);
 
    setupViewport(width(), height());
 
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glLoadIdentity();
    glTranslatef(0.0, 0.0, -10.0);
    glRotatef(xRot / 16.0, 1.0, 0.0, 0.0);
    glRotatef(yRot / 16.0, 0.0, 1.0, 0.0);
    glRotatef(zRot / 16.0, 0.0, 0.0, 1.0);
 
    glPushAttrib(GL_ALL_ATTRIB_BITS);
    qglColor(QColor(255, 239, 191));
    glBegin(GL_TRIANGLES);                     //draw 2 random triangles to test
	glVertex3f(+0.3, +0.3, -0.3);
	glVertex3f(-0.3, +0.3, -0.3);
	glVertex3f(+0.3, -0.3, -0.3);
	glVertex3f(-0.3, -0.3, -0.3);
	glVertex3f(+0.3, -0.3, +0.3);
     glVertex3f(-0.3, -0.3, +0.3);
     glEnd();
     glPopAttrib();
 
    glShadeModel(GL_FLAT);
    glDisable(GL_CULL_FACE);
    glDisable(GL_DEPTH_TEST);
    glDisable(GL_LIGHTING);
 
    glMatrixMode(GL_MODELVIEW);
    glPopMatrix();
}

void GLWidget::paintEvent(QPaintEvent *event)
{
	QPainter painter(this);
	painter.setPen(Qt::NoPen);
	painter.setBrush(gradient);
	painter.drawRect(rect());       //paint the background with linear gradient
	painter.end();

    makeCurrent();

    glMatrixMode(GL_MODELVIEW);
    glPushMatrix();
    glShadeModel(GL_SMOOTH);
    glEnable(GL_DEPTH_TEST);
    glEnable(GL_CULL_FACE);
    glEnable(GL_LIGHTING);
    glEnable(GL_LIGHT0);
    glEnable(GL_MULTISAMPLE);
    static GLfloat lightPosition[4] = { 0.5, 5.0, 7.0, 1.0 };
    glLightfv(GL_LIGHT0, GL_POSITION, lightPosition);

    setupViewport(width(), height());

    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glLoadIdentity();
    glTranslatef(0.0, 0.0, -10.0);
    glRotatef(xRot / 16.0, 1.0, 0.0, 0.0);
    glRotatef(yRot / 16.0, 0.0, 1.0, 0.0);
    glRotatef(zRot / 16.0, 0.0, 0.0, 1.0);

    glPushAttrib(GL_ALL_ATTRIB_BITS);
    qglColor(QColor(255, 239, 191));
    glBegin(GL_TRIANGLES);                     //draw 2 random triangles to test
	glVertex3f(+0.3, +0.3, -0.3);
	glVertex3f(-0.3, +0.3, -0.3);
	glVertex3f(+0.3, -0.3, -0.3);
	glVertex3f(-0.3, -0.3, -0.3);
	glVertex3f(+0.3, -0.3, +0.3);
     glVertex3f(-0.3, -0.3, +0.3);
     glEnd();
     glPopAttrib();

    glShadeModel(GL_FLAT);
    glDisable(GL_CULL_FACE);
    glDisable(GL_DEPTH_TEST);
    glDisable(GL_LIGHTING);

    glMatrixMode(GL_MODELVIEW);
    glPopMatrix();
}

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[franz]

Maybe the wolfenqt example can help you there.