first shot at twosided stereo; not clear how to combine these yet
fix bug in pairwise stereo
improve ch05ex06 to do disparity-based mapping
ch05ex04: plane sweeping with ssd
start with ch05ex02 by making a (more caching) copy of the 3d example
ch05ex02 wip: compute possible features
ch05ex02 wip: triangulate matches, improve feature matching (not working yet)
more ch05ex02. x2 is on the lhs of E.
ch05ex02 (finding additional features on epipoles) mostly works

For every feature in image 1, this finds all features in image 2 that
are within a small distance of the first image's feature's epipolar
line, and if there's only one and the corresponding feature descriptors
are reasonably close, the two points are considered as matching points.

This doesn't particularly well (yet?), since it has a bunch of false
positives and since it's always possible to triangulate two matching 2d
points to a single 3d point as long as camera transforms are known,
there's no built-in protection for false matches.