mrcal-show-stereo-pair-diff - Visualize the difference in projection between 2 camera pairs
$ mrcal-show-stereo-pair-diff \
--distance 2 \
before/camera-[01].cameramodel \
after/camera-[01].cameramodel
... a plot pops up showing how these two pairs differ in their projectionsTHIS TOOL IS EXPERIMENTAL, AND LIKELY WILL BE CHANGED AND EXTENDED. MORE COMPLETE DOCUMENTATION WILL BE WRITTEN LATER
It is useful to evaluate the stability and uncertainty of a multi-camera system, looking at the intrinsics,extrinsics either separately or jointly. For instance, when deployed in the field a calibration may shift in the extrinsics (camera units moved) and/or intrinsics (lens moved), and it would be useful to quantify them individually. Up to now (version 2.5) mrcal has been concerned mostly with the intrinsics: the mean-pcam uncertainty method and implied_Rt10__from_unprojections() try to compensate for and eliminate the effect of extrinsic shifts in uncertainty and diff methods respectively.
This stereo_pair_diff() tool extends this in one way: in a multi-camera calibration, it quantifies the joint intrinsics+extrinsics shift of a camera pair. At a given distance this tool reprojects pixels in camera0 to camera1, and compares the results of this reprojection. This is actually far simpler than the earlier intrinsics-only methods: no implied transform or reference-frame shift need to be considered. As of mrcal 2.5 we also have an extrinsics-only stereo-pair diff in an unreleased analyses/extrinsics-stability.py tool. No corresponding uncertainty method is implemented yet, but that is straightforward. All the methods will be implemented in a future mrcal release. They can then be studied to see what is useful to look at in practice.
This tool visualizes the results of mrcal.stereo_pair_diff()
models 4 camera models: 2 cameras from the first camera pair,
followed by 2 cameras from the other pair-h, --help show this help message and exit
--gridn GRIDN GRIDN How densely we should sample the imager. By default we
use a 60x40 grid
--distance DISTANCE The projection difference varies depending on the
range to the observed world points, with the queried
range set in this argument. If omitted we look out to
infinity.
--observations If given, I show where the chessboard corners were
observed at calibration time. These should correspond
to the low-diff regions.
--valid-intrinsics-region
If given, I overlay the valid-intrinsics regions onto
the plot
--cbmax CBMAX Maximum range of the colorbar
--title TITLE Title string for the plot. Overrides the default
title. Exclusive with --extratitle
--extratitle EXTRATITLE
Additional string for the plot to append to the
default title. Exclusive with --title
--vectorfield Plot the diff as a vector field instead of as a heat
map. The vector field contains more information
(magnitude AND direction), but is less clear at a
glance
--vectorscale VECTORSCALE
If plotting a vectorfield, scale all the vectors by
this factor. Useful to improve legibility if the
vectors are too small to see
--hardcopy HARDCOPY Write the output to disk, instead of making an
interactive plot
--terminal TERMINAL gnuplotlib terminal. The default is good almost
always, so most people don't need this option
--set SET Extra 'set' directives to gnuplotlib. Can be given
multiple times
--unset UNSET Extra 'unset' directives to gnuplotlib. Can be given
multiple timeshttps://www.github.com/dkogan/mrcal
Dima Kogan, <dima@secretsauce.net>
Copyright (c) 2017-2023 California Institute of Technology ("Caltech"). U.S. Government sponsorship acknowledged. All rights reserved.
Licensed under the Apache License, Version 2.0 (the "License"); You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0