I’ve been following this topic and it seems an issue dear to many. I’m trying to understand it better so I’ll just jump in and see if I am getting it.
First off the lid camera is a fisheye view of the bed so its optically distorted in a spherical pattern from center to edge. That’s a given.
It seems to correct this a factory profile is loaded that corrects most but not all distortion. On top of that the amount of correction is modulated by the thickness value you report for your material. Fudging this will sometimes result in better image accuracy but its not consistent.
The problem is the alignment of camera image to reality is affected by the lid opening and closing and the bed shifting slightly in use… so that factory file quickly goes bad.
I worked for years in the medical imaging field and we have this same issue of distortion introduced by various non linearities in optics and receptors. The answer for that and perhaps for this, is routine calibration. A calibrating phantom is put in the field of view… the image is taken and the software generates a new correction file. This is well known in imaging science.
It would seem that the accuracy of the bed image would be enhanced if a least once a week a cal program is done. First a grid phantom is placed on the bed and a perfect digital representation is displayed as an overlay. If the two align perfectly then no calibration is needed. If not then a camera image is taken and the error between the detected lines of the camera image and the calibration file’s perfect image lines would be the correction file. After cal. the camera image and the overlay should match.
Is this what Snapmark is trying to do?