Better error message on calibration failure
When the reprojection error of the extrinsic calibration is too high (avg. of more than 20cm), the user gets an error. However, the error only shows
"Error: Could not calculate extrinsic calibration. Please select other 2D/3D point "
"correspondences for extrinsic calibration!"
It would be more helpful to say that the error is too high (maybe mentioning the current error and the maximum error)
@a.kandler also noted that it may be helpful to have a warning with an even lower error (e.g. 10cm); still allowing the calibration to be used, but notifying the user that it is of rather bad quality.