would fail on coplanar faces (or smooth verts).
Loop remapping is really a tricky topic... For now, we enhance a bit more
our Frankenfunc by using distance between dest and source polygons as
fallback in case we have too much similar normals...
Probably not a perfect solution, but should be robust enough I hope.
One core question remains open though: do we want to stick to 'use only seams
to detect UV islands'? This makes things much simpler, but will obviously fail
in case of actual islands without matching seams. :/
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