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


Qt Code: 
  1. void GLWidget::paintEvent(QPaintEvent *event)
  2. {
  3. 	QPainter painter(this);
  4. 	painter.setPen(Qt::NoPen);
  5. 	painter.setBrush(gradient);
  6. 	painter.drawRect(rect());       //paint the background with linear gradient
  7. 	painter.end();
  8.  
  9.     makeCurrent();
  10.  
  11.     glMatrixMode(GL_MODELVIEW);
  12.     glPushMatrix();
  13.     glShadeModel(GL_SMOOTH);
  14.     glEnable(GL_DEPTH_TEST);
  15.     glEnable(GL_CULL_FACE);
  16.     glEnable(GL_LIGHTING);
  17.     glEnable(GL_LIGHT0);
  18.     glEnable(GL_MULTISAMPLE);
  19.     static GLfloat lightPosition[4] = { 0.5, 5.0, 7.0, 1.0 };
  20.     glLightfv(GL_LIGHT0, GL_POSITION, lightPosition);
  21.  
  22.     setupViewport(width(), height());
  23.  
  24.     glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  25.     glLoadIdentity();
  26.     glTranslatef(0.0, 0.0, -10.0);
  27.     glRotatef(xRot / 16.0, 1.0, 0.0, 0.0);
  28.     glRotatef(yRot / 16.0, 0.0, 1.0, 0.0);
  29.     glRotatef(zRot / 16.0, 0.0, 0.0, 1.0);
  30.  
  31.     glPushAttrib(GL_ALL_ATTRIB_BITS);
  32.     qglColor(QColor(255, 239, 191));
  33.     glBegin(GL_TRIANGLES);                     //draw 2 random triangles to test
  34. 	glVertex3f(+0.3, +0.3, -0.3);
  35. 	glVertex3f(-0.3, +0.3, -0.3);
  36. 	glVertex3f(+0.3, -0.3, -0.3);
  37. 	glVertex3f(-0.3, -0.3, -0.3);
  38. 	glVertex3f(+0.3, -0.3, +0.3);
  39.      glVertex3f(-0.3, -0.3, +0.3);
  40.      glEnd();
  41.      glPopAttrib();
  42.  
  43.     glShadeModel(GL_FLAT);
  44.     glDisable(GL_CULL_FACE);
  45.     glDisable(GL_DEPTH_TEST);
  46.     glDisable(GL_LIGHTING);
  47.  
  48.     glMatrixMode(GL_MODELVIEW);
  49.     glPopMatrix();
  50. }
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