title: Opengl drawing a 2d overlay on a 3d scene problem
body: <p>I have a moving 3d scene set up, and I want to make a stationary 2d GUI overlay that is always on top, when I try making 2d shapes I don't see anything. When I call: glMatrixMode(GL_PROJECTION);  my 3d scene disappears and I'm left with a blank window...</p>
  
  <p>here is the code I'm using for the overlay</p>
  
  <p>EDIT: updated code</p>
  
  <pre><code>    glMatrixMode(GL_MODELVIEW);
  glLoadIdentity();
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  gluOrtho2D(-100, 100, -100, 100);
  glDisable(GL_DEPTH_TEST);
  glDisable(GL_CULL_FACE);
  glDisable(GL_TEXTURE_2D);
  glDisable(GL_LIGHTING);
  glColor3f(1, 1, 1);
  glPushMatrix();
  glBegin(GL_QUADS); 
  glVertex3f(-5.0f, 5.0f, 0.0f); 
  glVertex3f(-5.0f, -5.0f, 0.0f); 
  glVertex3f(5.0f, -5.0f, 0.0f); 
  glVertex3f(5.0f, 5.0f, 0.0f); 
  glEnd();   
  glPopMatrix();
  glEnable(GL_DEPTH_TEST);
  glutSwapBuffers();
  </code></pre>