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fix(#185): landblock collision part-id uint32 overflow dropped stair steps

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Root cause (live capture #3 + code): GameWindow's per-part landblock shadow
registration used a synthetic part-id `entity.Id * 256u + partIndex` that
OVERFLOWS uint32 for class-prefixed landblock ids (0x40/0x80/0xC0...). The << 8
drops the prefix byte, so different-class entities sharing the low 24 bits
collide on ONE shadow part-id and Register's deregister-then-insert silently
overwrites one entity's collision geometry. Landblock 0xF682 had 23 such
collisions incl. the stair runs (0xF6822100 <- {0x40F68221, 0xC0F68221}, ...),
so 3 mid-staircase steps rendered but had no collision -> the player floats into
the hole and the (faithful) PrecipiceSlide wedge fires = the 'invisible wall
half-way up the stairs'.

Fix (Option A, retail-faithful): register each multi-part landblock entity via
ShadowObjectRegistry.RegisterMultiPart under its UNIQUE 32-bit entity.Id
(retail CPhysicsObj::add_shadows_to_cells 0x00514ae0 -> CPartArray::AddPartsShadow
- one object, a part array; no synthetic per-part id). New testable builder
ShadowShapeBuilder.FromLandblockBspParts decomposes each MeshRef.PartTransform to
local pos/rot/scale; RegisterMultiPart reconstructs the identical world placement.
Building shells stay excluded (building channel); the Setup cyl/sphere path is
unchanged (runs only when entityBsp==0, retail BSP-xor-cyl dispatch). Despawn is
landblock-scoped (RemoveLandblock by cell prefix), so the id change is safe.

Tests: ShadowRegistrationOverflowTests (overflow arithmetic; old scheme drops one;
RegisterMultiPart keeps both; builder). Issue185OutdoorStairsSeamReplayTests
(dat-free clean-climb pin). Core 2629 / App 741 green, 0 warnings.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
This commit is contained in:
Erik 2026-07-08 10:07:50 +02:00
parent b62b13ce21
commit 07c5b832cf
6 changed files with 897 additions and 67 deletions
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99
src/AcDream.App/Rendering/GameWindow.cs
View file

@ -7896,77 +7896,42 @@ public sealed class GameWindow : IDisposable
// docs/superpowers/specs/2026-05-21-cylinder-fallback-dedup-design.md.
bool _isLandblockStab = (entity.Id & 0xFF000000u) == 0xC0000000u;
if (_isScenery) scTried++;
// Register EACH physics-enabled part so multi-part Setups
// (buildings, trees) have all their collision geometry registered.
// Each part gets its own ShadowEntry with its world-space transform.
var entityRoot =
System.Numerics.Matrix4x4.CreateFromQuaternion(entity.Rotation) *
System.Numerics.Matrix4x4.CreateTranslation(entity.Position);
uint partIndex = 0;
foreach (var meshRef in entity.MeshRefs)
// #185 FIX (2026-07-08): register the entity's BSP parts as ONE
// multi-part shadow object keyed on the entity's UNIQUE 32-bit id,
// via RegisterMultiPart (retail CPhysicsObj::add_shadows_to_cells
// 0x00514ae0 → CPartArray::AddPartsShadow — one object, a part array).
//
// The former per-part Register(entity.Id * 256u + partIndex) OVERFLOWED
// uint32 for class-prefixed landblock ids (0x40/0x80/0xC0…): the << 8
// dropped the prefix byte, so different-class entities sharing the low
// 24 bits collided on ONE shadow part-id and Register's
// deregister-then-insert silently overwrote one entity's collision
// geometry — the #185 "invisible wall half-way up the stairs" (rendered
// steps with no collision; 23 such part-id collisions in landblock
// 0xF682 alone: 0xF6822100 ← {0x40F68221, 0xC0F68221}, …). entity.Id is
// unique, so RegisterMultiPart has no synthetic id and no collision.
// Building shells stay excluded (they collide via the per-LandCell
// building channel, CSortCell::find_collisions). The Setup CylSphere/
// Sphere path below is UNCHANGED and only runs when entityBsp == 0
// (retail binary dispatch: BSP xor cyl). Builder:
// ShadowShapeBuilder.FromLandblockBspParts.
var bspShapes = AcDream.Core.Physics.ShadowShapeBuilder.FromLandblockBspParts(
entity.MeshRefs, entity.IsBuildingShell,
id => _physicsDataCache.GetGfxObj(id));
entityBsp = bspShapes.Count;
if (entityBsp > 0)
{
// BR-7 / A6.P4 (2026-06-11): building SHELLS are not shadow
// objects in retail — their collision is the per-LandCell
// building channel (CSortCell::find_collisions, Ghidra
// 0x005340a0, dispatched off the CacheBuilding entry at the
// building's origin landcell). Registering them here is what
// put the cottage GfxObj into the radial sweep's reach from
// the cellar (#98). Interior statics + outdoor stab objects
// (LandBlockInfo.Objects) remain shadow objects.
if (entity.IsBuildingShell) break;
var partCached = _physicsDataCache.GetGfxObj(meshRef.GfxObjId);
if (partCached?.BSP?.Root is null) { partIndex++; continue; }
// Compute the part's world-space position from its transform.
var partWorld = meshRef.PartTransform * entityRoot;
// Decompose to extract scale (scenery objects have it baked
// into PartTransform), rotation, and translation.
System.Numerics.Vector3 partScale3;
System.Numerics.Quaternion partRot;
System.Numerics.Vector3 partPos;
if (System.Numerics.Matrix4x4.Decompose(partWorld,
out partScale3, out partRot, out partPos))
{ /* decompose succeeded */ }
else
{
partScale3 = System.Numerics.Vector3.One;
partRot = entity.Rotation;
partPos = new System.Numerics.Vector3(partWorld.M41, partWorld.M42, partWorld.M43);
}
// Use uniform scale (X component) — AC objects are uniformly scaled.
float partScale = partScale3.X;
if (partScale <= 0f) partScale = 1f;
// Local bounding sphere radius × world scale = world-space radius
// for the broad phase. The BSPQuery will also use `partScale` to
// transform player spheres into the unscaled BSP coordinate space.
float localRadius = partCached.BoundingSphere?.Radius ?? 1f;
float worldRadius = localRadius * partScale;
// Use a unique sub-ID per part: entity.Id * 256 + partIndex.
uint partId = entity.Id * 256u + partIndex;
_physicsEngine.ShadowObjects.Register(
partId, meshRef.GfxObjId,
partPos, partRot, worldRadius,
_physicsEngine.ShadowObjects.RegisterMultiPart(
entity.Id, entity.Position, entity.Rotation, bspShapes,
0u, AcDream.Core.Physics.EntityCollisionFlags.None,
origin.X, origin.Y, lb.LandblockId,
AcDream.Core.Physics.ShadowCollisionType.BSP, 0f,
partScale,
seedCellId: entity.ParentCellId ?? 0u);
seedCellId: entity.ParentCellId ?? 0u, isStatic: true);
// L.2d slice 1 (2026-05-13): [entity-source] greppable from [resolve-bldg].
// partCached?.BSP?.Root non-null was checked above (else `continue`),
// so hasPhys=true on this path.
// state/flags literals: landblock-baked scenery has no server PhysicsState
// broadcast and no PWD bitfield; defaults match static-solid semantics.
// One line per BSP part, all under the entity's single id (no synthetic partId).
if (AcDream.Core.Physics.PhysicsDiagnostics.ProbeBuildingEnabled)
Console.WriteLine(System.FormattableString.Invariant(
$"[entity-source] id=0x{partId:X8} entityId=0x{entity.Id:X8} src=0x{entity.SourceGfxObjOrSetupId:X8} gfxObj=0x{meshRef.GfxObjId:X8} lb=0x{lb.LandblockId:X8} type=BSP note=partIdx={partIndex} hasPhys=true state=0x{0u:X8} flags={AcDream.Core.Physics.EntityCollisionFlags.None}"));
entityBsp++;
partIndex++;
for (int _pi = 0; _pi < bspShapes.Count; _pi++)
Console.WriteLine(System.FormattableString.Invariant(
$"[entity-source] id=0x{entity.Id:X8} entityId=0x{entity.Id:X8} src=0x{entity.SourceGfxObjOrSetupId:X8} gfxObj=0x{bspShapes[_pi].GfxObjId:X8} lb=0x{lb.LandblockId:X8} type=BSP note=multipart-part{_pi} hasPhys=true state=0x{0u:X8} flags={AcDream.Core.Physics.EntityCollisionFlags.None}"));
}
// Register collision shapes from the Setup (if this entity has one).

79
src/AcDream.Core/Physics/ShadowShapeBuilder.cs
View file

@ -1,6 +1,7 @@
using System;
using System.Collections.Generic;
using System.Numerics;
using AcDream.Core.World;
using DatReaderWriter.DBObjs;
using DatReaderWriter.Enums;
using DatReaderWriter.Types;
@ -129,6 +130,84 @@ public static class ShadowShapeBuilder
return result;
}
/// <summary>
/// #185: build BSP shapes for a landblock-baked multi-part entity (buildings,
/// stair runs, fences, rock clusters) from its per-part <see cref="MeshRef"/>s,
/// for registration via <see cref="ShadowObjectRegistry.RegisterMultiPart"/>
/// under the entity's SINGLE unique id.
///
/// <para>
/// Replaces the former per-part <c>Register(entity.Id * 256u + partIndex)</c>
/// (GameWindow.cs) whose <c>* 256u</c> OVERFLOWED uint32 for class-prefixed
/// landblock ids (<c>0x40</c>/<c>0x80</c>/<c>0xC0</c>…): the overflow dropped
/// the prefix byte, so different-class entities sharing the low 24 bits
/// collided on one shadow part-id and <c>Register</c>'s deregister-then-insert
/// silently overwrote one entity's collision geometry — the #185 "invisible
/// wall half-way up the stairs" (rendered steps with no collision).
/// </para>
///
/// <para>
/// Retail anchor: a multi-part object is one <c>CPhysicsObj</c> + <c>CPartArray</c>;
/// <c>CPhysicsObj::add_shadows_to_cells</c> (0x00514ae0) → <c>CPartArray::AddPartsShadow</c>
/// walks the part array under the single object — no synthetic per-part id.
/// </para>
///
/// <para>
/// Each part's local transform comes from its <see cref="MeshRef.PartTransform"/>
/// (root-relative), decomposed to LocalPosition/LocalRotation/Scale;
/// <c>RegisterMultiPart</c> reconstructs the world placement identically
/// (<c>entityWorldPos + rotate(LocalPosition, entityWorldRot)</c>). Building
/// shells are excluded — they collide via the per-LandCell building channel
/// (<c>CSortCell::find_collisions</c>), not as shadow objects.
/// </para>
/// </summary>
/// <param name="meshRefs">The entity's per-part mesh references.</param>
/// <param name="isBuildingShell">True for <c>LandBlockInfo.Buildings[]</c> shells.</param>
/// <param name="getGfxObj">Resolves a GfxObj id to its cached physics (BSP +
/// bounding sphere). Production: <c>id => cache.GetGfxObj(id)</c>.</param>
public static List<ShadowShape> FromLandblockBspParts(
IReadOnlyList<MeshRef> meshRefs,
bool isBuildingShell,
Func<uint, GfxObjPhysics?> getGfxObj)
{
if (getGfxObj is null) throw new ArgumentNullException(nameof(getGfxObj));
var shapes = new List<ShadowShape>();
// Building shells collide via the building channel (retail), not shadow objects.
if (isBuildingShell || meshRefs is null) return shapes;
foreach (var meshRef in meshRefs)
{
var phys = getGfxObj(meshRef.GfxObjId);
if (phys?.BSP?.Root is null) continue; // no physics BSP → nothing to collide
// PartTransform is root-relative; decompose to local pos/rot/scale.
if (!Matrix4x4.Decompose(meshRef.PartTransform,
out var pScale, out var pRot, out var pPos))
{
pScale = Vector3.One;
pRot = Quaternion.Identity;
pPos = new Vector3(meshRef.PartTransform.M41,
meshRef.PartTransform.M42,
meshRef.PartTransform.M43);
}
float partScale = pScale.X > 0f ? pScale.X : 1f; // AC objects are uniformly scaled
float localRadius = phys.BoundingSphere?.Radius ?? 1f;
shapes.Add(new ShadowShape(
GfxObjId: meshRef.GfxObjId,
LocalPosition: pPos,
LocalRotation: pRot,
Scale: partScale,
CollisionType: ShadowCollisionType.BSP,
Radius: localRadius * partScale,
CylHeight: 0f));
}
return shapes;
}
/// <summary>Resolve the placement frame in priority Resting → Default →
/// first available. Mirrors <c>SetupMesh.Flatten</c>'s convention.</summary>
private static AnimationFrame? ResolvePlacementFrame(Setup setup)