Two parallel research agents converged on this bug. acdream's
ValidateTransition was setting OnWalkable based on `Normal.Z >= LandingZ`
(0.087, ~85° permissive) instead of `Normal.Z >= FloorZ` (0.664, ~49°
strict). Effect: a 60° roof slope (normal.Z = 0.5) was being marked
OnWalkable, letting the player walk freely up surfaces retail blocks.
Per retail PhysicsObj::is_valid_walkable
(acclient_2013_pseudo_c.txt:277180-277193) and ACE
PhysicsObj.cs:2861, the canonical "walkable" predicate is FloorZ.
LandingZ is the more permissive threshold used only in airborne→ground
transitions (Path 6 Collide handler) where we want to accept a brief
landing before the next frame's strict FloorZ check rejects the surface
and CliffSlide kicks in.
Three sites fixed:
1. Step-down branch's `zVal` initial value (was unconditional LandingZ;
now `oi.GetWalkableZ()` returns FloorZ when OnWalkable, LandingZ
otherwise — matches retail's transitional_insert step-down OK
branch at acclient_2013_pseudo_c.txt:273258-273265).
2. ValidateTransition's live-contact OnWalkable test (LandingZ → FloorZ).
3. ValidateTransition's LastKnown-fallback OnWalkable test (LandingZ →
FloorZ).
After this commit:
- Walking horizontally INTO a 60° slope: step-up's WalkableAllowance
is FloorZ (when OnWalkable), find_walkable rejects the slope's
polygon, step-up fails, StepUpSlide. Player blocked from climbing.
- Jumping ONTO a 60° roof: Path 6 still uses LandingZ (correct, we
want to land), so the player lands. Next frame: ValidateTransition
sees Normal.Z=0.5 < FloorZ → OnWalkable cleared. Player is Contact
but not OnWalkable. Currently this leaves them STUCK on the roof
(no CliffSlide yet to push them off). That's still better than
walking up the roof.
Full slide-off-roof + edge-slide-along-balcony behaviors require
porting CliffSlide + PrecipiceSlide + adding Walkable polygon
reference — that's Phase L.4 (~12-20h, sketched out by both research
agents). This commit unblocks the worst of the steep-walk-up behavior
while the bigger port is being designed.
Test count 825/825 still pass. Build clean.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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