Your Blend Func for OpenGL is wrong. You are meant to use GL_SRC_ALPHA_SATURATE with GL_ONE. What you have it set up to do is alphablending not antialiasing. The line smooth hint also has no real effect on polygon antialiasing. You should do glHint GL_POLYGON_SMOOTH_HINT, GL_NICEST. That said, if you are going to do glEnable(GL_LINE_SMOOTH) then you can set the hint for line smoothing. I've found that these features are not always supported on all systems. On one of my systems line smoothing does not work and line width cannot be larger than about 2. Also I don't think that your DX and GL antialiasing is comparable. It looks like DX is doing full-screen multisampling. You can do that in OpenGL too (see the module mod forum), but it's not the same as doing individual polygon antialiasing which only antialiases the edges.