Task j112. Two changes to the TR_MOVEMENT=strafe engine, both OFF the shipped
tfil path; the binary default is still tfil.
CURVED WINGS: the candidate set was the straight 1-D line through the bot, which
a bounded segment always terminates at a wall. It is now an adaptive parabola
with the vertex on the bot:
point(y) = bot + yhat*y + xhat*kappa(y)*y^2
xhat is the unit vector away from the nearest wall(s) (summed inward normals, so
a corner yields the diagonal). kappa grows as the wall approaches and saturates
at TR_STRAFE_KAPPA; every wing point is clamped inside TR_STRAFE_WALL_SAFE, so
the wing FLATTENS and runs parallel to the wall instead of touching it. In open
space kappa == 0 and the wing is exactly the old straight line. The wing chord
at the reach tilts the heading band toward the interior by atan(kappa*reach)
(capped by TR_STRAFE_WING_MAX); the body still only turns slowly to follow that
tangent, never to face the target, and reversals are still setForward sign flips.
GUARANTEED ESCAPE: with every candidate over threshold the old fallback minimised
pathMaxHeat, whose gradient points AT the wall (the shortest path has the least
wall exposure), so the least-hot tile was the adjacent one and led further along
the wall. Near a wall the picker now ranks by the DESTINATION (farthest from the
wall, then coolest tile) and commands the sign whose velocity has a positive
component along the wall-away normal. That sign is re-asserted EVERY tick, so
speed*heading . away >= 0 while escape is active: the clearance cannot fall.
mode=escape reaches the [strafe] log. A mild wall-margin bias
(TR_STRAFE_WALL_BIAS) prefers higher-clearance tiles when near a wall.
GUI/log: the curved wings are drawn as an orange polyline (candidates follow the
curve), a white ray + ESCAPE label marks the escape, and the [strafe] line now
carries wall=<dist> kappa=<..> mode=<pick|fallback|escape|radial>.
Gates (offline, kinematic replay of the DrussGT fixtures; see
common_libs/tests/measure_strafe_wings.nim, plus the reused j108/j111 gates):
wall occupancy (within 54 px) falls 25.6->4.3 / 18.3->4.1 / 23.8->4.3 / 27.8->4.7
percent and the longest continuous wall run 191->31 / 49->25 / 208->47 / 246->27
ticks; corner-region occupancy 4.7->0.0 percent with the longest corner run
71->7. The escape sweep (3520 start x heading x enemy runs, 110k escape ticks)
shows ZERO per-tick guarantee violations and a worst corner run of 21 ticks.
Open-space parity is bit-identical (kappa == 0), reversals are still sign flips
(0 non-sign commands), and mean turn/speed are unchanged (OFF 4.42 deg/tick,
31.3 percent no-turn vs ON 4.45 / 30.7; reversal-interval entropy 5.309 -> 5.311
bits). The fixtures are OPEN-LOOP, so these are veto-capable checks, not a live
win claim.
