j148: bound the corridor by speed x ticks (TR_{TFIL,STRAFE}_CORRIDOR_TICKS, default 0 = to the wall); UNTESTED

common_libs/movements/the_floor_is_lava.nim

@@ -269,6 +269,31 @@ proc loadTfilHeatEnv*() =
 
 loadTfilHeatEnv()
 
+# ── Corridor LENGTH bound (TR_TFIL_CORRIDOR_TICKS, default 0 = to the wall) ──
+#
+# WHY: the shipped corridor is the rotated rectangle from the bullet to the
+# ARENA WALL, so one distant bullet blankets a 40px-wide swath across the whole
+# map. That is not physical: in `t` ticks a bullet covers `speed * t` px, and
+# `speed = 20 - 3*power`, so a fast (low-power) bullet's reach is LONG and a
+# slow one's is SHORT.
+#
+# WHAT: bound the corridor's LENGTH, nothing else — the heat inside the
+# surviving corridor is EXACTLY today's (`heatDecay(along/speed)` is unchanged),
+# so unlike the j119 time-indexed heat model this does NOT decay heat along the
+# corridor; it only removes corridor that no bullet will reach.
+var TfilCorridorTicks* = 0.0    ## 0 (default) = to the wall: byte-for-byte shipped
+
+proc loadTfilCorridorEnv*() =
+  TfilCorridorTicks = getEnvFloat("TR_TFIL_CORRIDOR_TICKS", 0.0)
+
+loadTfilCorridorEnv()
+
+proc corridorReach*(tWall, speed: float): float =
+  ## The ONE place the corridor length is decided, so the heat field and the
+  ## drawn outline can never disagree. `tWall` = distance to the wall along the
+  ## heading, `speed` = the ghost's own px/tick. 0 = to the wall (shipped).
+  if TfilCorridorTicks <= 0.0: tWall else: min(tWall, speed * TfilCorridorTicks)
+
 proc heatDecay*(dt: float): float =
   ## Fraction of a bullet's heat still present `dt` ticks before it arrives.
   ## Exactly 1.0 when the time model is off, so the default field is
@@ -506,6 +531,9 @@ type CorridorGeom = object
   bx, by: float       ## bullet origin
 
 proc corridorGeom(b: TrackedBullet, arenaWidth, arenaHeight: float): CorridorGeom =
+  ## `tMin` is the corridor LENGTH: the distance to the wall, bounded by
+  ## `corridorReach` (TR_TFIL_CORRIDOR_TICKS). Unset (0) -> exactly the wall
+  ## distance, so the shipped field and outline are byte-for-byte unchanged.
   let speed = sqrt(b.velX * b.velX + b.velY * b.velY)
   if speed < 0.001: return
   let dx = b.velX / speed
@@ -515,6 +543,7 @@ proc corridorGeom(b: TrackedBullet, arenaWidth, arenaHeight: float): CorridorGeo
   elif dx < 0.0: tMin = min(tMin, (0.0          - b.x) / dx)
   if dy > 0.0:   tMin = min(tMin, (arenaHeight - b.y) / dy)
   elif dy < 0.0: tMin = min(tMin, (0.0          - b.y) / dy)
+  tMin = corridorReach(tMin, speed)
   CorridorGeom(dx: dx, dy: dy, px: -dy, py: dx, tMin: tMin, bx: b.x, by: b.y)
 
 proc lavaAt(m: TFILModule, col, row: int): float =