visp_auto_tracker - distance issue and multi qr code detection

[vannem95]

I tried using a different qr code than the one on the git page and the pose is incorrect. I'm getting correct values if i use the qr code from the git page but the range is too small. I see that the pattern.xml has something to do with configuring the qr code How do i do detect a different qr code properly?

Also, does the marker need to have the black padding?

Also, is there a way to detect multiple qr codes?

Thanks in advance.

[fspindle]

If I understand you want to use a larger pattern. This is possible modifying:

• models/pattern.wrl (lines 13 to 20) with the new size in meter of the outer and inner squares (those surrounding the black padding). The outer is 0.07652 large, while the inner is 0.038252 meter large
• models/pattern.cao same as previous modifying lines 4 to 11
• should be checked, but maybe there is also models/calibration.ini that should be adapted to your camera parameters
• models/pattern.cfg lines 8 to 22 to set the 3D coordinates of the 4 QRcode corners (used to compute the pose of the QR code
• models/pattern.cfg lines 25 to 39 to set the 4 coordinates of the inner square (same as models/pattern.cao lines 17 to 20
• models/pattern.cfg lines 42 to 56 to set the 4 coordinates of the outer square (same as models/pattern.cao lines 13 to 16

I thing that the black padding is requested to detect if the tracker fails or not. Tracking failure is needed by the state machine to start a new QR code detection. The trackig failure detection is based on the gray level of some pixels (the cyan squares) that are located between the inner and outer square corners.

Never tried multiple QR codes but I don't think that the existing code is able to do that without modifications.

[eraserpencil]

How would I go about generating the QR codes and getting the data as needed? I'm looking at something low density (so no need for too many rows), long viewing distance (so large block size) and small footprint (as small as possible).

[guillermoherreraf]

@fspindle hi! I'm trying to track the same QR code you provide but in a smaller scale... I modified the pattern files as well as the calibration.ini and it still does not track the smaller QR code. However, it keeps tracking the one on the proper scale, which is weird as I modified the pattern configuration files. Any idea why this could be happening?

[slyandsmart]

Hi, I am working on visp_auto_tracker to do a chees game with my mobile robot. Is it somehow solved to recognice multiple QR Codes. As it is shown in the Apriltag-Example?

[fspindle]

Not tested, but I'm not sure that the code was designed to handle this situation.

In the next weeks we plan to port to ROS2. I will add this feature in the new version.