# OpenGL - Quad is being separated like a two triangles after blending

I wanted to add transparency for my UI elements, so I enabled blending by adding:

glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);


before renderer and

glDisable(GL_BLEND);


after renderer.

So I tried to render simple rectangle (with glDrawArrays() because I'm using GLSL shaders).

Before I enabled blending my rectangle (1 quad) looked like this:

And now, after blending it looks like this (Like a two triangles):

Do I need some extra settings for my blending or what?

Edit:

I noticed that if I remove anti-aliasing code:

glHint(GL_LINE_SMOOTH_HINT, GL_NICEST);
glHint(GL_POINT_SMOOTH_HINT, GL_NICEST);
glHint(GL_POLYGON_SMOOTH_HINT, GL_NICEST);
glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);

glEnable(GL_LINE_SMOOTH);
glEnable(GL_POINT_SMOOTH);
glEnable(GL_POLYGON_SMOOTH);


Problem will disappear, but I want to keep anti-aliasing in my game. Any ideas?