# Session Handoff — 2026-04-14

## What shipped this session

### Rendering rebuild (5 steps, all complete)
- Step 1: Instanced mesh rendering (DrawElementsInstanced, 800+ FPS)
- Step 2: Terrain chunk batching (16×16 ACME-style chunks)
- Step 3: AdjustPlanes lighting (ACME constants)
- Step 4: EnvCell portal visibility (BFS, conditional depth clear)
- Step 5: Animation already in instanced pipeline

### Movement (Layer 1 — working)
- Run speed from PlayerWeenie RunRate formula (Run skill 200 → 9.5 m/s)
- Charged jump with proper physics arc + server packet (0xF61B)
- Facing direction quaternion convention (AC heading via holtburger)
- Jump apex velocity zeroing bug fixed (SmallVelocity threshold)
- Airborne momentum preservation (no velocity replacement while jumping)

### Collision (partially working — needs full rewrite)
- ShadowObjectRegistry cell-based spatial index
- PhysicsDataCache stores GfxObj BSP + Setup CylSphere + CellStruct BSP
- BSPQuery with 6-path dispatcher (attempted but incomplete)
- CylSphere collision for trees/rocks
- SlideSphere crease-projection for wall sliding
- Multiple bug fixes (broad-phase, push-out, corner stuck, safety margins)

### Infrastructure
- docs/bugs.md for tracking known issues
- Movement completion design spec + implementation plan

## What did NOT work

The collision system was built by patching symptoms instead of porting
the retail code faithfully. After ~10 iterations of fixes, it handles
~60-70% of cases but still clips through some buildings, trees, and
objects. The user explicitly requested a full retail port — no shortcuts.

## Build/test state
- `dotnet build`: green, 0 errors
- `dotnet test`: 470 passed (361 core + 109 net), 0 failures
- All commits on main

## What to do next

**PORT THE RETAIL COLLISION SYSTEM FROM SCRATCH.**

The full plan is in `memory/project_collision_port.md`. The approach:

1. Read the decompiled function (ground truth)
2. Cross-reference ACE's C# (naming aid)  
3. Write pseudocode
4. Port line-by-line to C#
5. When ACE and decompiled disagree, decompiled wins

### Files to port (ACE → acdream):
- `Sphere.cs` → sphere-vs-sphere collision dispatcher (FUN_005387c0)
- `BSPTree.cs` → find_collisions 6-path dispatcher
- `BSPNode.cs` / `BSPLeaf.cs` → BSP traversal with movement
- `Polygon.cs` → pos_hits_sphere with FindTimeOfCollision
- `Transition.cs` → FindTransitionalPosition, TransitionalInsert
- `SpherePath.cs` → sphere state management
- `LandCell.cs` → outdoor terrain collision
- `EnvCell.cs` → indoor room collision
- `ObjCell.cs` → object collision + cell enumeration

### What to keep:
- CollisionPrimitives.cs (9 functions, faithfully ported from decompiled)
- PhysicsDataCache.cs (dat loading — correct)
- ShadowObjectRegistry.cs (cell bucketing — correct concept)
- PhysicsBody.cs, MotionInterpreter.cs, PlayerWeenie.cs (correct)

### What to replace:
- BSPQuery.cs — simplified, not retail-faithful
- TransitionTypes.cs Transition methods — patched, not retail-faithful
- PhysicsEngine.ResolveWithTransition — may need restructuring