I'm not sure if a bug report was ever filed on this.. but it is based on
this thread.
http://processing.org/discourse/yabb2/YaBB.pl?num=1250870750

Antialias does not work properly in recent processing versions unless you
first do a " hint(DISABLE_OPENGL_2X_SMOOTH);" Then you can reenable it or
smooth() or whatever. If you don't disable it first, you don't get the
best AntiAlias quality.

void setup() {
size(320,240,OPENGL);
hint(DISABLE_OPENGL_2X_SMOOTH);
//hint(ENABLE_OPENGL_4X_SMOOTH); //after disabling the 2x this works fine
smooth(); // this works even better than the 4x! super-smooth! ;)
}

Thanks for the report, nobody had bothered to post this yet, so I wasn't
aware that it was this prevalent. What hardware are you running? I also
suspect this depends heavily on the graphics hardware (thought I saw a
handful of MacBook Pros on that thread) as to the exact behavior.

The hint() vs. smooth() discrepancy is that smooth() makes the OpenGL
smoothing calls (or at least did previously), while the hint() just handles
FSAA. FSAA should almost always give better results in terms of overall
consistency (the GL smoothing calls tend to overdo it).

(In reply to comment #1)
>
>
>
> Additional Comment #1 From
> fry
> 2009-12-16 06:57
>
> <!--
> addReplyLink(1); //-->[reply]
>
>
>
>
> Thanks for the report, nobody had bothered to post this yet, so I
wasn't
> aware that it was this prevalent. What hardware are you running? I also
> suspect this depends heavily on the graphics hardware (thought I saw a
> handful of MacBook Pros on that thread) as to the exact behavior.
>
> The hint() vs. smooth() discrepancy is that smooth() makes the OpenGL
> smoothing calls (or at least did previously), while the hint() just handles
> FSAA. FSAA should almost always give better results in terms of overall
> consistency (the GL smoothing calls tend to overdo it).
>
>

I'm running a MacBook Pro with 10.6.2.
From what I understand and testing the bug, it's wasn't a hint() vs.
smooth() issue. Neither worked. Using "hint(DISABLE_OPENGL_4X_SMOOTH);
and "GL_LINE_SMOOTH" was just as ineffective as using smooth(). The
problem was that nothing worked correct until you first did a disable hint
for 2X_SMOOTH, then everything works fine (both hint() and smooth()).

So, it appears that there are in fact 4 states to opengl smoothing, where
processing assumes there are only 3:

States:
1) No antialiasing
2) Antialias, 2x
3) Antialias, 4x
4) Antialias, UNLIMITED

Where choice 2 is apparantly default, 4 is achieved by disabling #2 and
calling smooth() anyway.

No, there are four that are covered by Processing:

1. no smoothing, via noSmooth()
2. the default, which is 2x fsaa
3. 4x fsaa, by calling hint(4X)
4. smooth() which calls gl.glEnable(GL.GL_XXXXX_SMOOTH); methods, but is
ignored when FSAA is enabled (actually now i look and see that it's only
ignored on 2x, but should also be on 4x).