[Kwiver-users] Bounding Box Issues

[Matt Brown]

I was diagnosing an issue in a detection pipeline doing non-maximal
suppression that led me to observe that the area of the intersection of two
bounding boxes can be negative.

The intersection
<https://github.com/Kitware/kwiver/blob/master/vital/types/bounding_box.h#L276>
of two bounding boxes yields a bounding box representing the intersection.
Internally, the bboxes are Eigen::AlignedBox, and the intersection uses this
Eigen function
<https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=2ahUKEwiy1cj8hfngAhWnhOAKHRrsCtcQygQwAHoECAEQBg&url=https%3A%2F%2Feigen.tuxfamily.org%2Fdox%2FclassEigen_1_1AlignedBox.html%23title26&usg=AOvVaw1oBy2fk1j2WCPGlEGJnXOn>.
Still working on it, but I suspect that Eigen is returning an empty box
with junk for parameters (i.e., Eigen says "The result of most methods is
undefined when applied to an empty box").

So the question is, what should be returned here
<https://github.com/Kitware/kwiver/blob/master/vital/types/bounding_box.h#L279>
when there is no intersection? Should we define a special empty bbox
subclass?

Best,
Matt
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