docs(architecture): WorldBuilder inventory + CLAUDE.md alignment

Saves the comprehensive inventory of what WorldBuilder provides
(terrain, scenery, static objects, EnvCells, portals, sky, particles,
texture decode, mesh extraction, visibility) vs what acdream still
ports from retail decomp (network, physics, animation, movement, UI,
plugin, audio, chat).

This is the load-bearing reference for the strategic shift from
"port retail algorithms ourselves" to "rely on WorldBuilder for
rendering + dat-handling, port only what WB doesn't cover."

Updates CLAUDE.md:
- Adds top-level instruction: read the inventory FIRST before
  re-porting anything in the 🟢 list
- Reframes references/WorldBuilder/ as acdream's rendering BASE,
  not just a reference repo
- Updates the "Reference hierarchy by domain" table to point
  rendering/dat questions at WorldBuilder, with retail decomp as
  cross-check

Subsequent commits will fork WorldBuilder and replace our terrain/
scenery/object rendering with calls into the fork.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

CLAUDE.md

@@ -25,6 +25,19 @@ single source of truth for how the client is structured. All work must
 align with this document. When the architecture doc and reality diverge,
 update one or the other — never leave them out of sync.
 
+**WorldBuilder is acdream's rendering + dat-handling base** as of
+2026-05-08. Before re-implementing any AC-specific rendering or
+dat-handling algorithm, **read `docs/architecture/worldbuilder-inventory.md`
+FIRST**. If WorldBuilder has it, port from WorldBuilder (or call into
+our fork once wired up), not from retail decomp. WorldBuilder is
+MIT-licensed, verified to render the world correctly, and uses the same
+Silk.NET stack we target. Re-porting from retail decomp when WB already
+has a tested port is how subtle bugs (the scenery edge-vertex bug, the
+triangle-Z bug) keep slipping in. Retail decomp remains the oracle for
+network, physics, animation, movement, UI, plugin, audio, chat — see
+the inventory doc's 🔴 list for the full scope of "we still write this
+ourselves".
+
 **Execution phases:** R1→R8 in the architecture doc. Each phase has clear
 goals, test criteria, and builds on the previous. Don't skip phases.
 
@@ -625,11 +638,18 @@ these, ideally all four:
   for the palette-indexed formats. See
   `ACViewer/Render/TextureCache.cs::IndexToColor` for the canonical
   subpalette overlay algorithm.
-- **`references/WorldBuilder/`** — C# + Silk.NET dat editor. Exact-stack
-  match to acdream for rendering approaches: terrain blending, texture
-  atlases, shader patterns. Most useful for "how do I do this GL thing
-  with Silk.NET on net10 idiomatically?" Less useful for protocol or
-  character appearance (dat editor, not game client).
+- **`references/WorldBuilder/`** — **acdream's rendering + dat-handling
+  BASE (not just a reference).** As of 2026-05-08 acdream is moving to
+  fork WorldBuilder upstream and depend on the fork for terrain,
+  scenery, static objects, EnvCells, portals, sky, particles, texture
+  decoding, mesh extraction, visibility/culling. WorldBuilder is
+  MIT-licensed, exact-stack match (Silk.NET + .NET), and verified to
+  render the world correctly. **Before re-porting any rendering or
+  dat-handling algorithm from retail decomp, check
+  `docs/architecture/worldbuilder-inventory.md` first.** If WB has it,
+  use WB's port. If WB doesn't have it (network, physics, animation,
+  movement, UI, plugin, audio, chat), port from retail decomp as
+  before.
 - **`references/Chorizite.ACProtocol/`** — clean-room C# protocol
   library generated from a protocol XML description. Useful sanity check
   on field order, packed-dword conventions, type-prefix handling. The
@@ -684,12 +704,15 @@ decompiled client code and would have fixed it in minutes.
 
 | Domain | Primary Oracle | Secondary | Notes |
 |--------|---------------|-----------|-------|
-| **Any AC-specific algorithm** | **`docs/research/named-retail/`** (PDB-named decomp + verbatim retail header structs from Sept 2013 EoR build) | the existing references below | The retail client itself, fully named. 18,366 functions + 5,371 struct types + 1.4 M lines of pseudo-C in one searchable tree. Beats every other reference for "what does the real client do." |
-| **Terrain** (split direction, height sampling, palCode, vertex position, normals) | **ACME `ClientReference.cs`** — decompiled retail client with exact offsets | ACME `TerrainGeometryGenerator.cs` (matches the mesh index buffer) | WorldBuilder original is SUPERSEDED for terrain algorithms. AC2D confirms the same formula. |
-| **Terrain blending** (texture atlas, alpha masks, road overlays) | **ACME `LandSurfaceManager.cs`** | WorldBuilder original `LandSurfaceManager.cs` (same code, less tested) | Both use the same TexMerge pipeline. ACME has conformance tests. |
-| **GfxObj / Setup rendering** (mesh extraction, multi-part assembly, ObjDesc) | **ACME `StaticObjectManager.cs`** — includes CreaturePalette, GfxObjRemapping, HiddenParts | ACViewer `Render/` namespace | ACME has the complete creature appearance pipeline in one file. |
-| **Texture decoding** (INDEX16, P8, DXT, BGRA, alpha) | **ACME `TextureHelpers.cs`** | ACViewer `Render/TextureCache.cs` (palette overlay = `IndexToColor`) | For subpalette overlay specifically, ACViewer's `IndexToColor` is the canonical algorithm. |
-| **EnvCell / dungeon rendering** (cell geometry, portal visibility, collision mesh) | **ACME `EnvCellManager.cs`** — portal traversal, mixed landblock detection, collision cache | ACViewer `Physics/Common/EnvCell.cs` | ACME is significantly more complete than original WorldBuilder for dungeons. |
+| **Any AC-specific algorithm** | **`docs/research/named-retail/`** (PDB-named decomp + verbatim retail header structs from Sept 2013 EoR build) | the existing references below | The retail client itself, fully named. 18,366 functions + 5,371 struct types + 1.4 M lines of pseudo-C in one searchable tree. Beats every other reference for "what does the real client do." Use for everything in the 🔴 list (network, physics, animation, movement, UI, plugin, audio, chat). |
+| **Terrain** (split direction, height sampling, palCode, vertex position, normals) | **WorldBuilder `TerrainGeometryGenerator.cs` + `TerrainUtils.cs`** | retail decomp for cross-check | WB is acdream's terrain base. ACME's port is older/SUPERSEDED by WB. |
+| **Terrain blending** (texture atlas, alpha masks, road overlays) | **WorldBuilder `LandSurfaceManager.cs`** | ACME `LandSurfaceManager.cs` (same algo, less complete) | WB is acdream's blending base. |
+| **Scenery** (procedural placement: trees, bushes, rocks, fences) | **WorldBuilder `SceneryRenderManager.cs` + `SceneryHelpers.cs`** | retail decomp `CLandBlock::get_land_scenes` | WB is acdream's scenery base. Re-porting from retail decomp is what caused the edge-vertex bug. |
+| **GfxObj / Setup rendering** (mesh extraction, multi-part assembly, ObjDesc) | **WorldBuilder `StaticObjectRenderManager.cs` + `ObjectMeshManager.cs`** | ACME `StaticObjectManager.cs` (includes CreaturePalette, GfxObjRemapping, HiddenParts — useful for character appearance which WB doesn't cover) | WB for static objects, ACME for character appearance. |
+| **Texture decoding** (INDEX16, P8, DXT, BGRA, alpha) | **WorldBuilder `TextureHelpers.cs`** | ACME `TextureHelpers.cs`; ACViewer's `IndexToColor` is canonical for subpalette overlay | WB is acdream's decode base. |
+| **EnvCell / dungeon rendering** (cell geometry, portal visibility, collision mesh) | **WorldBuilder `EnvCellRenderManager.cs` + `PortalRenderManager.cs`** | ACME `EnvCellManager.cs` (more complete for collision); ACViewer `Physics/Common/EnvCell.cs` | WB is acdream's geometry base; ACME for collision until ported. |
+| **Particles / sky** (particle systems, weather, sky particles) | **WorldBuilder `SkyboxRenderManager.cs` + `ParticleEmitterRenderer.cs` + `ParticleBatcher.cs`** | retail decomp | WB is acdream's particle base. |
+| **Visibility / culling** (frustum, cell visibility) | **WorldBuilder `VisibilityManager.cs` + `Frustum.cs`** | — | WB. |
 | **Network protocol** (wire format, packet framing, fragment assembly, ISAAC) | **holtburger** `crates/holtburger-session/` | AC2D `cNetwork.cpp` (simpler, good for cross-check) | ACE shows the server side; holtburger + AC2D show the client side. |
 | **Client behavior** (what to send when, login flow, ack pattern, keepalive) | **holtburger** `crates/holtburger-core/src/client/` | AC2D `cNetwork.cpp` + `cInterface.cpp` | holtburger is the most complete; AC2D is simpler but confirmed working. |
 | **Movement** (MoveToState format, AutonomousPosition, sequence counters, speed) | **holtburger** `client/movement/` | AC2D `cNetwork.cpp:2592-2664` (0xF61C format) | See `docs/research/2026-04-12-movement-deep-dive.md` for the full cross-reference. |

docs/architecture/worldbuilder-inventory.md

@@ -0,0 +1,250 @@
+# WorldBuilder Inventory — what we take, adapt, or leave
+
+**Status:** load-bearing reference. As of 2026-05-08 acdream's strategy is
+to **rely heavily on WorldBuilder** for rendering and dat-handling rather
+than re-port retail algorithms ourselves. WorldBuilder is MIT-licensed, is
+verified by visual inspection to render the AC world correctly (terrain,
+scenery, slabs, dungeons, slopes, particles), and uses the same Silk.NET
++ .NET stack we already target.
+
+**Integration model:** **fork upstream WorldBuilder** at
+`github.com/Chorizite/WorldBuilder`, depend on our fork, delete editor-only
+code, expose hooks for our network state to feed scene data in. Sync with
+upstream via merge so we inherit fixes. This document tells you, before
+you write code, whether the thing you're about to port already exists in
+WorldBuilder.
+
+**Workflow change:** Before re-implementing any AC-specific rendering or
+dat-handling algorithm, **check this inventory first**. If WorldBuilder
+has it, port from WorldBuilder (or call into our fork once it's wired
+up), not from retail decomp. Retail decomp remains the oracle for things
+WorldBuilder lacks — animation, motion, physics collision, networking.
+
+---
+
+## Repo layout (as of cloned snapshot under `references/WorldBuilder/`)
+
+- **`Chorizite.OpenGLSDLBackend/`** — full OpenGL renderer (Silk.NET).
+- **`WorldBuilder.Shared/`** — data models, dat parsers, landscape module.
+- **`WorldBuilder/`** — Avalonia desktop app shell (NOT taken).
+- **`WorldBuilder.{Windows,Linux,Mac}/`** — platform entry points (NOT taken).
+- **`WorldBuilder.Server/`** — collab editing backend (NOT taken).
+- **`Tests/` + `WorldBuilder.Shared.Benchmarks/`** — test harness (study).
+
+**Upstream NuGet dependencies** (these stay as NuGet packages, we don't
+vendor them):
+
+| Package | Version | Purpose |
+|---|---|---|
+| `Chorizite.Core` | 0.0.18 | Plugin framework — contains `Chorizite.Core.Lib.BoundingBox`, `Chorizite.Core.Render.*` interfaces used by every render manager |
+| `Chorizite.DatReaderWriter` | 2.1.x | dat parsing (we already use 2.1.7) |
+| `Chorizite.DatReaderWriter.Extensions` | 1.1.x | extra dat helpers |
+| `BCnEncoder.Net` | 2.2.x | DXT decode (we already use) |
+| `SixLabors.ImageSharp` | 3.1.x | image loading |
+| `Silk.NET.OpenGL` + `Silk.NET.SDL` | 2.23.x | GL + windowing (we use Silk's own windowing, they use SDL) |
+| `MP3Sharp` | 1.0.5 | MP3 decode |
+
+---
+
+## 🟢 RENDERING — take wholesale or adapt
+
+These are what makes WB "perfect". Anything in this section, we should
+use from WB rather than re-implement.
+
+### Terrain
+
+| Component | What it does |
+|---|---|
+| `TerrainRenderManager` | Full pipeline (per-chunk GPU buffers, draw orchestration) |
+| `LandSurfaceManager` | Texture blending atlas (palCode, alpha masks, road overlays) |
+| `TerrainGeometryGenerator` | Heightmap → mesh, normals, OnRoad, GetHeight, GetNormal |
+| `TerrainChunk` | 16×16 landblock chunk geometry |
+| `TextureAtlasManager` | Texture atlas builder |
+| `VertexLandscape` | Terrain vertex format |
+
+### Scenery (procedural placement: trees, bushes, rocks, fences)
+
+| Component | What it does |
+|---|---|
+| `SceneryRenderManager` | Generate + render per-vertex scenery |
+| `SceneryHelpers` | Displace / RotateObj / ScaleObj / ObjAlign / CheckSlope |
+| `SceneryInstance` | Per-spawn instance data |
+
+### Static objects (buildings, slabs, props — Setup + GfxObj + ObjDesc)
+
+| Component | What it does |
+|---|---|
+| `StaticObjectRenderManager` | Master pipeline for static objects |
+| `ObjectRenderManagerBase` + `BaseObjectRenderManager` | Common render base |
+| `ObjectMeshManager` | Mesh extraction from Setup/GfxObj, ObjDesc application |
+
+### Dungeons / interiors
+
+| Component | What it does |
+|---|---|
+| `EnvCellRenderManager` | Dungeon interior cell geometry |
+| `PortalRenderManager` | Portal traversal / visibility |
+
+### Sky + atmosphere
+
+| Component | What it does |
+|---|---|
+| `SkyboxRenderManager` | Skybox rendering |
+| `ParticleEmitterRenderer` + `ParticleBatcher` + `ActiveParticleEmitter` | Particle systems (sky particles, weather, magic) |
+
+### Visibility / culling
+
+| Component | What it does |
+|---|---|
+| `VisibilityManager` + `VisibilitySnapshot` | Frustum + cell visibility |
+| `Frustum` | Frustum-cull math |
+
+### Other rendering helpers
+
+| Component | What it does |
+|---|---|
+| `MinimapRenderer` | Top-down minimap |
+| `GlobalMeshBuffer` | Shared GPU mesh buffer |
+| `GpuResourceManager` | GPU resource lifecycle |
+| `InstanceData` | Instanced draw data |
+| `TextureHelpers` | INDEX16, P8, BGRA, DXT decode + alpha (canonical port) |
+| `DebugRenderer` + `DebugRendererLineDrawer` + `EdgeLineBuilder` | Debug primitives |
+
+### Shaders (22 total)
+
+Located at `Chorizite.OpenGLSDLBackend/Shaders/`:
+
+`Landscape.{vert,frag}` · `StaticObject.{vert,frag}` · `StaticObjectModern.{vert,frag}` · `Particle.{vert,frag}` · `PortalStencil.{vert,frag}` · `Outline.{vert,frag}` · `Simple3D.{vert,frag}` · `InstancedLine.{vert,frag}` · `Text.{vert,frag}` · `UI.{vert,frag}` · `Gizmo.{vert,frag}` (editor-only)
+
+---
+
+## 🟢 LOW-LEVEL GL / FRAMEWORK — take or replace with our own
+
+Either take WB's wrappers wholesale, or keep our own and adapt the
+render managers to use ours. These wrappers are stateless or
+near-stateless and are the easiest to swap.
+
+| Component | What it does |
+|---|---|
+| `OpenGLGraphicsDevice` | Silk.NET.OpenGL wrapper |
+| `OpenGLRenderer` | Render orchestration |
+| `GLSLShader` | Shader compile/link/uniforms |
+| `GLHelpers` + `GLStateScope` | GL state utility |
+| `ManagedGLFrameBuffer` / `ManagedGLIndexBuffer` / `ManagedGLTexture` / `ManagedGLTextureArray` / `ManagedGLUniformBuffer` / `ManagedGLVertexArray` / `ManagedGLVertexBuffer` | GL resource wrappers |
+| `TextureParameters` | Sampler config |
+| `GpuMemoryTracker` | Memory tracking |
+| `Camera2D` / `Camera3D` / `CameraBase` / `ICamera` / `CameraController` | Camera primitives |
+| `GameScene` + `SingleObjectScene` + `SceneData` + `ModernRenderData` + `RenderPass` | Scene / pass structures |
+
+---
+
+## 🟢 GEOMETRY / MATH UTILS — take wholesale
+
+| Component | File |
+|---|---|
+| `TerrainUtils` (OnRoad, GetNormal, GetHeight, GetRoad, palCode) | `WorldBuilder.Shared/Modules/Landscape/Lib/TerrainUtils.cs` |
+| `TerrainCacheManager` | `…/Lib/TerrainCacheManager.cs` |
+| `TerrainRaycast` | `…/Lib/TerrainRaycast.cs` |
+| `GeometryUtils` | `WorldBuilder.Shared/Lib/GeometryUtils.cs` |
+| `RaycastingUtils` (ray-vs-sphere/AABB/triangle) | `WorldBuilder.Shared/Lib/RaycastingUtils.cs` |
+| `DoubleNumerics` (double-precision Vector/Matrix) | `WorldBuilder.Shared/Lib/DoubleNumerics.cs` |
+| `DatUtils` | `WorldBuilder.Shared/Lib/DatUtils.cs` |
+| `BoundingBoxExtensions` | `Chorizite.OpenGLSDLBackend/Lib/BoundingBoxExtensions.cs` |
+
+---
+
+## 🟢 DATA MODELS — take selectively
+
+| Component | What it does |
+|---|---|
+| `RegionInfo` | Landblock metadata wrapper (LandblockSizeInUnits, CellSizeInUnits, etc.) |
+| `TerrainEntry` | Per-vertex terrain (Type/Scenery/Road/Height) |
+| `MergedLandblock` | Merged dat data |
+| `CellSplitDirection` | SW-NE vs NE-SW |
+| `Cell` | Generic cell wrapper |
+| `ObjectId` | Object identifier |
+| `Position` | World position |
+| `ACEnums` | AC-specific enums |
+| `WbBuildingPortal` / `WbCellPortal` | Portal structures |
+| `BuildingObject` | Building data |
+
+---
+
+## 🟡 EDITOR-ONLY — leave behind / delete in fork
+
+These exist for the editor experience and have no place in a game
+client. Delete in fork.
+
+- **`Modules/Landscape/Tools/*`** — `BrushTool`, `BucketFillTool`,
+  `RoadLineTool`, `RoadVertexTool`, `InspectorTool`,
+  `ObjectManipulationTool`, `Gizmo*` (DragHandler, HitTester, Renderer,
+  State), `TexturePainting*`, `SceneRaycaster`,
+  `LandscapeBrush`, `LandscapeToolBase`, `LandscapeToolContext`,
+  `IToolSettingsProvider`, `ILandscapeBrush`, `ILandscapeEditorService`,
+  `ILandscapeRaycastService`, `ILandscapeTool`, `ITexturePaintingTool`
+- **`Modules/Landscape/Commands/*`** — undo/redo command pattern for
+  editor (Add/Delete/Move/Rename/Reorder/etc.)
+- **`LandscapeDocument` + `LandscapeLayer` + `LandscapeLayerGroup` + `LandscapeChunk` + `LandscapeLayerChunk` + `LandscapeLayerBase`** — editor document model
+- **`Modules/Landscape/Models/TerrainPatch*` + `LandblockChangedEventArgs`** — editor mutation events
+- **`Modules/Landscape/Services/ILandscapeCacheService` + `ILandscapeDataProvider` + `ILandscapeObjectService` + impls** — editor data flow
+- **All `Migrations/*`** — SQLite schema migrations (project file format)
+- **`Repositories/*`** + **`Services/*`** — project storage, dat repository, AceDb, SignalR sync, document manager, undo stack, world coordinates, keyword DB, project migration, semantic kernel AI helpers
+- **`Hubs/*`** — collaborative editing via SignalR
+- **`StaticObject` (editor model)** — replace with our own scene-state data model fed from network
+- **`BackendGizmoDrawer` + `GizmoRenderer`** — editor gizmos
+- **`ProjectStructures, IProject, Project`** — editor project files
+- **`KeyBinding`** — editor input binding
+- **`ViewportInputEvent[Extensions]`** — editor viewport input
+- **`EditorState`** — editor state container
+
+---
+
+## 🟡 AUDIO / FONT — we already have alternatives
+
+Keep ours; don't take theirs.
+
+- **`AudioPlaybackEngine`** — uses MP3Sharp. We have OpenAL.
+- **`FontRenderer`** — uses ImageSharp. We have BitmapFont/StbTrueTypeSharp + ImGui.
+
+---
+
+## 🔴 NOT IN WORLDBUILDER — port from retail decomp ourselves
+
+WorldBuilder is a dat editor; it does not have:
+
+- **Network protocol** — UDP framing, ISAAC, packet codec, ACE message
+  layer (we have this; oracle is `references/holtburger`)
+- **Physics** — collision (CPhysicsObj transitions, BSP queries, sphere
+  sweeps), step-up, walkable validation (we have partial; oracle is the
+  retail decomp at `docs/research/named-retail/`)
+- **Animation** — motion sequencer, cycle/non-cycle parts, animation
+  frame interpolation (we have this; oracle is retail decomp)
+- **Movement** — local player WASD → MoveToState wire, remote-entity
+  motion via UpdateMotion + dead-reckoning (we have this; oracle is
+  `references/holtburger` + retail decomp)
+- **Game UI** — chat, vitals, inventory, spell book, allegiance, options
+  (we have this; ImGui-based today, custom-toolkit later)
+- **Plugin API** — `IGameState`, `IEvents`, `IActions`, `IPacketPipeline`,
+  `IOverlay` (we have this — acdream-unique)
+- **Game events** — combat, allegiance, spell casting, quest events
+  (we have this; oracle is ACE for opcodes + retail for client behavior)
+- **Audio** — OpenAL pipeline, sound triggers (we have this)
+- **TurbineChat** + **slash commands** (we have this)
+- **Login + character selection flow** (we have this)
+
+---
+
+## What this means for the workflow
+
+The CLAUDE.md "grep named → decompile → verify → port" workflow stays
+the rule for everything in the 🔴 list (network, physics, animation,
+movement, UI, plugin, audio, chat). For anything in 🟢, the new rule is:
+**check this inventory FIRST**. If WB has it, port from WB. Re-porting
+from retail decomp when WB already has a tested port is no longer
+appropriate — that's how we got the scenery edge-vertex bug.
+
+When the inventory says "take wholesale or adapt" and we discover a
+behavior mismatch with retail (rare — WB is verified), the resolution
+is: reconcile WB ↔ retail decomp ↔ holtburger ↔ ACE ↔ ACViewer (the
+existing reference hierarchy in CLAUDE.md). WorldBuilder ranks at the
+top of that hierarchy for anything 🟢.