CPhysicsObj::FindObjCollisions at pc:276961-276989 has a two-layer mechanism for
ethereal doors. Layer 1 (BSPQuery Path-1 sphere_intersects_solid, pc:323742) already
ported in Task 3 handles the open-gap case. Layer 2 (pc:276963-276977) is a
force-reset that catches the residual case: when the player's sphere CENTER crosses
a thin ethereal slab, sphere_intersects_solid can still return Collided via
HitsSphere (polygon contact on the slab face). Without Layer 2, the opened door
remains an invisible wall until the player's center passes ~0.48m beyond the slab.
Port: in FindObjCollisionsInCell, immediately after the shape dispatch (BSP / Sphere /
Cylinder branches), insert the Layer-2 gate:
if (result != OK && sp.ObstructionEthereal && !sp.StepDown && (obj.State & 0x1u) == 0)
{ result = OK; ci.CollisionNormalValid = false; }
The STATIC_PS (0x1) guard (pc:276969) ensures static-ethereal env geometry still
blocks. Cylinder/Sphere shapes already return OK from their own ObstructionEthereal
early-outs so Layer 2 is effectively BSP-only in practice, but is written
unconditionally matching retail.
Tests (ObstructionEtherealTests): three new BSP Layer-2 cases using a synthetic
wall polygon in local-space coordinates. (A) ethereal non-static: passable. (B)
ethereal+static: still blocks. (C) non-ethereal: still blocks. All 11 tests pass;
DoorCollision/CellarUp/CornerFlood/HouseExitWalk regression gate: 25/25 pass.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Retail oracle greps confirmed:
- CSphere::intersects_sphere @ 0x00537ae4 (pc:321692): the ethereal branch
is `void __thiscall` — all paths return void (no COLLIDED). The function
performs a proximity check only; no blocking result is produced.
- CCylSphere::intersects_sphere @ 0x0053b4a0 (pc:324573): same void-return
pattern — ethereal branch calls collides_with_sphere (check only, no slide),
all returns are void = passable.
Change: added `if (sp.ObstructionEthereal) return TransitionState.OK` at the
top of SphereCollision and CylinderCollision in TransitionTypes.cs, mirroring
the void-return semantics of both retail functions. The existing per-object
clear at pc:276989 (line 2837) still fires after the early OK return.
Before this fix: an ethereal-alone NPC/ghost with a Cylinder or Sphere shadow
shape would BLOCK the player (regression introduced when Task 3 made ETHEREAL-
alone fall through ShouldSkip instead of instant-skipping). After: all three
shape types — BSP (via BSPQuery Path 1), Sphere, and Cylinder — correctly pass
through when obstruction_ethereal is set.
Tests: added 4 tests to ObstructionEtherealTests.cs verifying:
- Ethereal Cylinder → passable (sweep passes through, no CollisionNormalValid)
- Ethereal Sphere → passable (same)
- Non-ethereal Cylinder → still blocks (regression guard)
- Non-ethereal Sphere → still blocks (regression guard)
Full Core suite: 1584 pass, 0 fail, 2 skip (pre-existing dat skips).
Pseudocode doc updated with confirmed cyl/sphere ethereal contracts and the
complete set/clear/consume flow summary.
Retail refs:
- CSphere::intersects_sphere @ 0x00537ae4 / acclient_2013_pseudo_c.txt:321692
- CCylSphere::intersects_sphere @ 0x0053b4a0 / acclient_2013_pseudo_c.txt:324573
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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>
