Using OpenCV (with python) I wrote a little AR application that uses only some basic OpenCV functionality. I did this mainly to get a slight idea on the quality of my calibrated intrinsic and, of course, for the fun of it. If I get this more clean and stable I will add the source code here. Maybe together with my great intrinsic video camera calibration tool.

Thanks to this little script, I have noted the incredible high importance of the accuracy of the camera's intrinsic for the quality and accuracy of the calculated extrinsic. While this might be somehow obvious, it is still quite impressive. Calibrating the camera's intrinsic over and over again until I have reached an acceptable level of accuracy, I have been able to reduce the square error (present in the main project I am workin on) by a factor of almost 7, together with good undistortion I even reach a total factor of 70.

As cvFindChessboardCorners does not appear to be very robust or fast, it is still quite nice to use it for this kind of fun - without needing those annoying libraries like ARTag or ARToolkit (which, nevertheless, have their moments, of course).