The topic is already discussed but with the different perspective -
check this link:- http://forums.adobe.com/message/4306492#4306492
the reason is the corner effect doesn't form the perfect semi -circle at the end.
Thank you. I can see now where the corners are not forming proper semicircles.
However this observation is a little different. Not only are the corners not circular, they are not all the same. Any corner matches the opposite corner, but it doesn't match the other two. In other words, a flip changes the shape, but a 180° rotation does not.
I'm just finding the time to play with this, and that is, indeed an interesting observation.
It has nothing to do with Live Corner Effects, per se -- I see the same thing in CS3 where you can "round the square" and also when running the cornereffects script in CS5 as a comparison. One of the things I tried was making a square and running the corner effects script in CS5 to make the corner radii meet properly without the flatspot, duplicating that, then converting the duplicate to an ellipse. When selecting the individual path points on the ellipse with the direct select tool you get two control handles, each half the length of the spcified radius, and on the round-corner rectangle you get only one, radius length, control handle, and I think that's the source of the asymmetry. You don't get to see the handles on the rectangles to which you've added corner effects using the corner effects options, however. ID still considers them as "Rectangles" in the layers panel, while a shape created by running the script becomes a "Path."
I guess this make some logical sense. Until you start playing these kinds of tricks the curve you create with the single handle is acceptably circular, and it allows for simpler constructions. In the round corner rectangle the corners are created with a single node still on the perimeter of the rectangle. To use symmetrical handles you'd have to have two nodes at the corner, one at each tangent point.
To get perfect rounded corners use a script like "EckenEffekte_504d.js" by Hans Haesler at:
There are another two scripts that enhance the feature set of that script:
Caution: all in German, just test them, if they fit your needs…