Ideas from StereoKit (MIT, 07b9f0d), credited where a formula comes from it:
- The torso faces the head's forward counted twice plus the direction to
each wrist seen (POINTER_RAY_TORSO_WRISTS, on), so looking aside while
pointing swings the shoulders, and the ray, less. probe-moves replay: the
shoulder's share of a still hand's ray motion 20 -> 18%, p90 2.0-3.7 ->
1.7-3.6 deg/s; the tap capture: nothing worse.
- The ray can turn toward the hand's own direction, from the palm's axes
(wrist, middle, ring and little knuckles) tilted -30/8 deg
(POINTER_RAY_HAND_WEIGHT, 0). Off: every weight measured worse (at 0.3:
judder 0.07-0.14 -> 0.11-0.33 deg rms per 90 Hz tick, raw jumps over
3 deg 159 -> 330). The gate still tests the shoulder's ray.
- The knuckle point can be pinned to the palm's axes during a pinch, easing
back on the steady shoulder's schedule (POINTER_RAY_ANCHOR, 0). Off: our
pinch point is the knuckles already, and pinned it shook as much or more
and kicked no less on release, fitted or not.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
hands/include/fh_ray.h, shared by the pointer helper and ft-screens (design
sections 2.4-2.5): a body model (torso yaw = head yaw low-passed, at most
30 deg behind; shoulders from it), the ray from the shoulder through the
knuckles (20 ms prediction), the pointing gate (show tests for 120 ms,
hide after 250 ms of a failed keep test; near and "off" hide at once;
held through a ray pinch), and One Euro filters on yaw, pitch and origin.
- pointer/tests/handray-test.cpp: body, gate timing and tests, filter
(just test-c).
- ft-handreplay --ray FILE: per set and hand, what the helper reads.
- pointer/tools/rayeval: the ray over a replay, with the head poses from the
ft-handtest probe's log of the same session (clock matched by the
published capture times): how often it shows, why not, jitter, the ray's
shift into a pinch.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
