Calibration of upside down cameras

[pedroperrusi]

Hey,

First of all, thanks for the great quality open source tool.

I've been using Vicalib to calibrate multiple Realsense D400 camera pairs and its been performing well for almost all cases. It handles fine the translation as well as a z-axis 90 degree rotation between camera pairs.

Although, when I attempt to calibrate a camera pair upside down to one another, with a rotation of 180 degrees on the z-axis. The calibration takes a long time to converge and leads to bad results.

I'm currently using the small calibration pattern preset and always leaving its text facing up when calibrating.

An example call is: vicalib -cam realsense2:[id0=832112070477,id1=832112073478,size=1280x720,rgb=1,ir0=0,ir1=0,depth=0,emitter=0]// -grid_preset small -alsologtostderr true

Are there any known limitations to the cameras orientation?
I appreciate any solutions you can propose and I'm available to post more information if necessary.

Cheers,
Pedro