No pinch begins while the index and middle are both curled (tip-to-wrist
under fist_curl times knuckle-to-wrist, Grip's curl measure), and a close
held back so has to open past end_m before one can begin. A pinch already
down carries on. A fist puts the thumb tip on the curled index, and live
ft-hands read 96% of fist frames in the flags as pinched.
1.2 rather than the flag analysis' 1.3: the model's world landmarks read
pinching fingers more curled. Replays (student v11c) against the tap
labels: clear non-fist pinches lost 2 of 204 at 1.2 (4 at 1.3), labelled
fists read as pinches 8 -> 5.
ft-handreplay: --pinch-fist-curl, the guard's count in the summary, the
finger curls in the timeline. The flag manifest's settings gain
pinch_dip and pinch_fist_curl.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Quick taps with the hand raised often read 25-30 mm at contact and spring
back without reaching the 2 cm begin, so they never click. With
HANDS_PINCH_DIP=1 (ft-hands --pinch-dip, ft-handreplay --pinch-dip) a pinch
also begins on a sharp dip: within 150 ms the distance falls by 40% of its
recent highest to under 3.2 cm, with the palm moving under 0.3 m/s and the
thumb at least 4 cm from the middle fingertip. It ends 6 mm over its lowest,
or becomes an ordinary pinch once the tips get within 2 cm. Off by default;
the middle pinch doesn't use it.
Guided tap capture replay (student v4): quick taps on a 2 Hz click 10 -> 25
of 30, clear teacher taps 0.62 -> 0.74 at precision 0.93 -> 0.91. Near
misses (fingers ~1 cm apart) now click: 5 -> 16 pinches in that segment.
Unit tests in tests/pinch_test.cpp.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
A pinch held 0.3 s or longer (a drag) ends only once the tips are 5 cm apart, or 0.12 s
after they first went past 3.5 cm without closing back under 3 cm. Drags in the 2026-10-09
headset test ended with the tips 3.5-4.0 cm apart. A grip takes a pinch only within 0.3 s
of its begin (closing the hand into a fist); after that no grip begins on that hand, so
curling the other fingers around a held pinch doesn't drop it (3 of 28 pinches in the same
test). Taps end as before.
On the lit recording's replayed distances, pinches held 0.3 s or more ended 33-134 ms later
than before, 200 at most. tests/pinch_test.cpp (make check).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
