"Look closer" tiles the frame so a small subject reaches a fixed 640x640 model
at its own size. A tile sees only the part of an object inside it, so an object
on a seam produces two *partial* masks — neither of them the object.
This kept the higher-scoring one and discarded the other, which quietly threw
away what tiling had just been paid 2.8 seconds for: a bird with its tail cut
off at a tile edge, described by whichever tile happened to hold more of the
bird. Both halves existed; one survived.
They are unioned now, and the overlap is what makes that sound. At 25% every
pixel is seen by at least one tile at full resolution and pixels near a seam by
two, so the pointwise maximum is the better estimate everywhere rather than a
compromise: where one tile saw a pixel its opinion is the only one there is,
and where both did, the higher value came from the tile with more context
around it. A maximum of soft coverage also stays soft, which is what `prior.rs`
weights merges by and what a mask layer's edge treatment needs.
Each quantity gets the operation that suits it: maximum for coverage, union
for the box, and the higher score rather than a blend — the score is shown to a
photographer and means "how sure the model is this is a bird", so averaging in
a tile that saw a wingtip would make a confident detection look doubtful for
straddling a seam.
The test fails against the old rule with "pixel 4 was seen by a tile and must
survive the merge", which is the whole defect in one line: not a crash, not a
duplicate, just a plausible mask missing half its subject.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
dtourolleandClaude Opus 5
7a5e1adf51