Every XR frame in the cockpit seat the pacing thread locates both grips in
the seated frame (the immersive base turned by the lean-back angle, the
frame the eye transforms place the vehicle in) and publishes a driving
snapshot. The wheel or handlebar shows the left stick's steering at the
configured full-lock angle, eased; the vehicle's own wheel reads that angle
on the guest thread.
With hand_steering on (off by default), squeezing a grip near the wheel or
handlebar takes hold of it (a short pulse on grab and release); one or two
hands turn it through heurazy's SteeringWheel, and while it is held the
wheel replaces the left stick's X axis in both the Wii Remote and gamepad
presentations, the stick's Y still aims items, and a holding grip no
longer presses C or a shoulder. The settings panel withholds it like any
other input.
The stereo packet carries the cockpit overlay: the hands, in the runtime's
hand mesh (XR_EXT_hand_tracking + XR_FB_hand_tracking_mesh, requested only
when hand steering is on at launch) or procedural gloves, and the separate
VR wheel or handlebar whenever the vehicle's own is not the one turning.
The pure pieces of the first-person cockpit and hand steering, ported from
heurazy's mario-kart-wii-VR-port: the SteeringWheel grab/turn model, the
native wheel vertex rotation, the level seat stabiliser, the seated-eye and
wheel/handlebar geometry, and the XR_FB_hand_tracking_mesh loader. Adds
openxr_driving.h, the OpenXR-free snapshot the pacing thread will publish for
the guest thread, with the hand-off rule (a held wheel replaces the left
stick's X and releases that hand's grip for the game) and the wheel's
displayed angle.
New [vr] keys: first_person_seat (cockpit), cockpit_units_per_meter (100),
steering_wheel (true), native_steering_wheel (true), hand_steering (false)
and the seven wheel_* tuning keys. Nothing reads them yet.
The fresh-config template now writes the first-person defaults the
constants hold (50 / 1.5 / 0); d86dcb0 updated the constants but not the
template.
Tests: mkw_steering_wheel_tests (the fork's), mkw_vr_cockpit_tests,
mkw_vr_hand_steering_tests.
iChris4