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fix(physics): #137 Task 3 — port obstruction_ethereal verbatim; retire AD-7 shim

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Retail CPhysicsObj::FindObjCollisions (0x0050f050) only instant-skips when
BOTH ETHEREAL_PS (0x4) AND IGNORE_COLLISIONS_PS (0x10) are set (pc:276782).
ETHEREAL-alone sets sphere_path.obstruction_ethereal=1 (pc:276806) and
continues to the shape dispatch. BSPTREE::find_collisions (0x0053a496) routes
Path 1 (sphere_intersects_solid) when the flag is set (pc:323742): the open
door has no solid leaf at the doorway, so the test returns OK → player passes
through. CEnvCell::find_env_collisions (0x0052c144) clears the flag first so
ENV walls are never weakened (pc:309580, "D5 clear").

Changes:
- CollisionExemption.ShouldSkip: require BOTH bits for Gate-1 early-out
  (previously ETHEREAL alone returned true — the AD-7 shim). Divergence
  register row AD-7 deleted.
- SpherePath: add ObstructionEthereal field (mirrors retail
  SPHEREPATH.obstruction_ethereal).
- FindObjCollisionsInternal loop: set sp.ObstructionEthereal=(target&0x4)!=0
  before shape dispatch; clear it after (per-object clear pc:276989).
  Also clear at the null-BSP continue site to keep flag clean.
- FindEnvCollisions: clear sp.ObstructionEthereal=false at top (D5 clear
  pc:309580) — ENV cell walls are always solid.
- BSPQuery.FindCollisions Path 1: change `obj.Ethereal` (ObjectInfo.Ethereal,
  always false — dead code) to `path.ObstructionEthereal`. Gate now correctly
  mirrors retail pc:323742: PLACEMENT_INSERT || obstruction_ethereal.

Consume site change (BSPQuery.cs before/after):
  BEFORE: if (path.InsertType == InsertType.Placement || obj.Ethereal)
  AFTER:  if (path.InsertType == InsertType.Placement || path.ObstructionEthereal)
Mirrors retail pc:323742 exactly. obj.Ethereal was dead code (ObjectInfo.Ethereal
is never set true anywhere); the correct flag is SpherePath.ObstructionEthereal.

Tests: 1580 pass / 0 fail / 2 skip (was 1576/0/2 + 4 new in ObstructionEtherealTests.
CellarUp, CornerFlood, DoorCollision, HouseExitWalk all green — no wall regressions.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
This commit is contained in:
Erik 2026-06-24 19:20:02 +02:00
parent 78e5758185
commit 3361a8d776
7 changed files with 382 additions and 30 deletions
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31
src/AcDream.Core/Physics/CollisionExemption.cs
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@ -59,23 +59,20 @@ public static class CollisionExemption
public static bool ShouldSkip(uint targetState, EntityCollisionFlags targetFlags,
ObjectInfoState moverState)
{
// 1. Target ETHEREAL → walk through.
// Retail (acclient_2013_pseudo_c.txt:276782) requires BOTH
// ETHEREAL_PS (0x4) AND IGNORE_COLLISIONS_PS (0x10) to wrap
// the entire body of FindObjCollisions and skip collision.
// ETHEREAL alone takes a different retail path (line 276795
// sets sphere_path.obstruction_ethereal = 1 and downstream
// movement allows passage despite the contact). We haven't
// ported that downstream path yet.
//
// L.2g slice 1b (2026-05-13): ACE's Door.Open() sends only
// ETHEREAL (state=0x0001000C observed live), not the
// ETHEREAL|IGNORE_COLLISIONS combo retail servers broadcast.
// Pragmatic shortcut: exempt on ETHEREAL alone so doors
// become passable when ACE flips the bit. Retail-server
// broadcasts (state=0x14+) still hit this branch correctly
// because both bits set implies ETHEREAL set.
if ((targetState & ETHEREAL_PS) != 0)
// 1. Target ETHEREAL + IGNORE_COLLISIONS → instant-skip.
// Retail (acclient_2013_pseudo_c.txt:276782):
// `if ((state & 4) AND (state & 0x10)) return 1`
// BOTH bits are required. ETHEREAL-alone takes the retail
// `obstruction_ethereal` path instead (pc:276806): the flag is
// set to 1 on the SpherePath and the shape test still runs,
// but BSP Path 1 (sphere_intersects_solid) weakens solid-
// containment so the player passes through the open door.
// ACE's Door.Open() broadcasts ETHEREAL only (0x0001000C) —
// this faithful port makes open doors passable via the BSP
// sphere_intersects_solid path (no solid leaf at the opening),
// which subsumes the former AD-7 shim. Divergence register
// row AD-7 retired in the same commit as this change.
if ((targetState & ETHEREAL_PS) != 0 && (targetState & IGNORE_COLLISIONS_PS) != 0)
return true;
// 2. Viewer mover + creature target → walk through.