# Phase B.3 Complete — Movement and World Navigation Implementation Plan

> **For agentic workers:** REQUIRED SUB-SKILL: Use superpowers:subagent-driven-development (recommended) or superpowers:executing-plans to implement this plan task-by-task. Steps use checkbox (`- [ ]`) syntax for tracking.

**Goal:** Complete the physics collision engine with CellPortal-based indoor transitions, jump with gravity, portal-space teleport handling, and scenery/step-height fixes.

**Architecture:** Extend `PhysicsEngine.Resolve` with portal-plane crossing detection for indoor/outdoor transitions. Add vertical velocity + gravity to `PlayerMovementController`. Add a portal-space state machine triggered by `PlayerTeleport` server messages. Fix scenery road exclusion and step-height from Setup dat.

**Tech Stack:** .NET 10, System.Numerics, DatReaderWriter, xUnit.

**Spec:** `docs/superpowers/specs/2026-04-12-b3-complete-movement-design.md`

---

## File structure

```
src/AcDream.Core/Physics/
  PortalPlane.cs                       [new] portal plane record + crossing test
  PhysicsEngine.cs                     [modify] add portal planes to LandblockPhysics,
                                                replace disabled indoor branch with
                                                portal-plane crossing logic
  CellSurface.cs                       [no change — portals live on PhysicsEngine]

src/AcDream.App/Input/
  PlayerMovementController.cs          [modify] add jump/gravity/airborne state,
                                                Space input, ledge-fall detection

src/AcDream.Core.Net/
  WorldSession.cs                      [modify] add PlayerTeleport handler + event

src/AcDream.App/Rendering/
  GameWindow.cs                        [modify] portal-space state machine, populate
                                                portal planes at load time, pass
                                                Setup.StepUpHeight, wire Space input

src/AcDream.Core/World/
  SceneryGenerator.cs                  [modify] add road terrain-type exclusion

tests/AcDream.Core.Tests/Physics/
  PortalPlaneTests.cs                  [new]
  PhysicsEngineTests.cs                [modify] add portal transition + landblock
                                                boundary tests

tests/AcDream.Core.Tests/Input/
  PlayerMovementControllerTests.cs     [modify] add jump/gravity/fall tests

tests/AcDream.Core.Tests/World/
  SceneryGeneratorTests.cs             [new] road exclusion test
```

---

## Task 1: PortalPlane (record + plane math + crossing test)

**Files:**
- Create: `src/AcDream.Core/Physics/PortalPlane.cs`
- Test: `tests/AcDream.Core.Tests/Physics/PortalPlaneTests.cs`

Pure math — no dependencies on the rest of the physics engine. Build the portal plane record with a static crossing-detection method.

- [ ] **Step 1: Write failing tests**

Create tests covering: plane construction from 3 vertices, crossing detection (positions on opposite sides), no crossing (positions on same side), crossing at exact plane.

```csharp
// PortalPlaneTests.cs
[Fact] FromVertices_ComputesCorrectNormal()
[Fact] IsCrossing_PositionsOnOppositeSides_ReturnsTrue()
[Fact] IsCrossing_PositionsOnSameSide_ReturnsFalse()
[Fact] IsCrossing_StartOnPlane_ReturnsFalse()
```

- [ ] **Step 2: Implement PortalPlane**

Create `src/AcDream.Core/Physics/PortalPlane.cs`:

```csharp
namespace AcDream.Core.Physics;

public readonly record struct PortalPlane(
    Vector3 Normal,
    float D,
    uint TargetCellId,    // OtherCellId (0xFFFF = outdoor)
    uint OwnerCellId,     // the EnvCell that owns this portal
    ushort Flags)
{
    public static PortalPlane FromVertices(
        Vector3 v0, Vector3 v1, Vector3 v2,
        uint targetCellId, uint ownerCellId, ushort flags)
    {
        var edge1 = v1 - v0;
        var edge2 = v2 - v0;
        var normal = Vector3.Normalize(Vector3.Cross(edge1, edge2));
        float d = -Vector3.Dot(normal, v0);
        return new PortalPlane(normal, d, targetCellId, ownerCellId, flags);
    }

    /// <summary>
    /// Test whether the movement from oldPos to newPos crosses this plane.
    /// Returns true if the two positions are on opposite sides.
    /// </summary>
    public bool IsCrossing(Vector3 oldPos, Vector3 newPos)
    {
        float oldDist = Vector3.Dot(Normal, oldPos) + D;
        float newDist = Vector3.Dot(Normal, newPos) + D;
        // Different signs = crossed the plane. Ignore near-zero (on the plane).
        return oldDist * newDist < 0f;
    }
}
```

- [ ] **Step 3: Run tests, commit**

```bash
git commit -m "feat(core): Phase B.3 — PortalPlane (plane math + crossing detection)"
```

---

## Task 2: PhysicsEngine portal-based indoor transitions

**Files:**
- Modify: `src/AcDream.Core/Physics/PhysicsEngine.cs`
- Modify: `tests/AcDream.Core.Tests/Physics/PhysicsEngineTests.cs`

Replace the `if (false)` disabled branch with real CellPortal plane-crossing logic.

- [ ] **Step 1: Extend LandblockPhysics record**

Add `IReadOnlyList<PortalPlane> Portals` to the record and `AddLandblock` signature.

- [ ] **Step 2: Write failing tests**

Add to `PhysicsEngineTests.cs`:
```csharp
[Fact] Resolve_OutdoorThroughPortal_TransitionsToIndoor()
[Fact] Resolve_IndoorThroughPortal_TransitionsToOtherCell()
[Fact] Resolve_IndoorThroughExitPortal_TransitionsToOutdoor()
[Fact] Resolve_LandblockBoundary_PicksAdjacentTerrain()
```

Each test constructs a fake portal plane at a known position and asserts cell ID changes when the movement crosses it.

- [ ] **Step 3: Implement portal crossing in Resolve**

Replace the `if (false)` block. The logic:

For **outdoor** players: test all portals in the current landblock where `TargetCellId != 0xFFFF` (outside-facing portals have OwnerCellId = building entry; TargetCellId = 0xFFFF means the portal FACES outside, so from outside you enter the OwnerCellId). Actually, the outside-facing portals should be tested from the outdoor side — when `IsCrossing` is true, the player enters the `OwnerCellId`.

For **indoor** players: test only portals belonging to the current cell. Get them by filtering on `OwnerCellId == currentCellId`. On crossing, transition to `TargetCellId` (or outdoor if `TargetCellId == 0xFFFF`).

**IMPORTANT:** Read the spec section 1 carefully. Also read `references/ACViewer/ACViewer/Physics/Common/EnvCell.cs` for the canonical transition logic. The `PortalFlags.PortalSide` flag may affect which direction the crossing triggers. Implementation should follow ACViewer's pattern.

- [ ] **Step 4: Update the existing indoor-transition test**

`Resolve_EnterIndoorCell_StaysOutdoor_BecauseTransitionDisabled` should be renamed to `Resolve_OutdoorThroughPortal_TransitionsToIndoor` and updated to use a portal plane instead.

- [ ] **Step 5: Run tests, commit**

```bash
git commit -m "feat(core): Phase B.3 — CellPortal-based indoor/outdoor transitions in PhysicsEngine"
```

---

## Task 3: Populate portal planes from streaming

**Files:**
- Modify: `src/AcDream.App/Rendering/GameWindow.cs` (ApplyLoadedTerrainLocked)

- [ ] **Step 1: Extract portal planes at landblock load time**

In `ApplyLoadedTerrainLocked`, after the existing CellSurface construction loop, add a second loop that extracts portal planes from each EnvCell:

For each EnvCell:
  For each CellPortal in envCell.CellPortals:
    Look up the polygon via `cellStruct.PhysicsPolygons[portal.PolygonId]` (note: the key type is ushort; cast PolygonId)
    Get the first 3 vertex positions from the polygon's VertexIds
    Transform to world space (same transform already used for CellSurface vertices)
    Create a `PortalPlane.FromVertices(v0, v1, v2, portal.OtherCellId, envCellId & 0xFFFF, (ushort)portal.Flags)`
    Add to a `List<PortalPlane>`

Pass the portal list to `_physicsEngine.AddLandblock`.

**IMPORTANT:** The portal's `PolygonId` indexes `CellStruct.Polygons` (rendering polygons), NOT `CellStruct.PhysicsPolygons`. Verify by reading the CellPortal definition — the PolygonId is used in ACViewer's `CellStructure.Polygons[portal.PolygonId]`. Check which dictionary it actually indexes. If it's the rendering Polygons dict, use that instead.

- [ ] **Step 2: Build + test (no new unit tests — verified via Task 2's integration tests + live run)**

```bash
git commit -m "feat(app): Phase B.3 — populate portal planes from streaming pipeline"
```

---

## Task 4: Jump + gravity + falling

**Files:**
- Modify: `src/AcDream.App/Input/PlayerMovementController.cs`
- Modify: `tests/AcDream.Core.Tests/Input/PlayerMovementControllerTests.cs`
- Modify: `src/AcDream.App/Rendering/GameWindow.cs` (wire Space key)

- [ ] **Step 1: Add MovementInput.Jump field**

Add `bool Jump = false` to the `MovementInput` record.

- [ ] **Step 2: Add airborne state to PlayerMovementController**

Add fields:
```csharp
public float VerticalVelocity { get; private set; }
public bool IsAirborne { get; private set; }
public float JumpImpulse { get; set; } = 10f;
public float GravityAccel { get; set; } = 20f;
public float AirControlFactor { get; set; } = 0.2f;
```

- [ ] **Step 3: Implement jump/gravity in Update**

After horizontal movement resolution, add:
- On Space + onGround + !IsAirborne: set VerticalVelocity = JumpImpulse, IsAirborne = true
- If IsAirborne: apply gravity, check if landed (candidateZ <= groundZ)
- If !IsAirborne and resolved Z is significantly below current Z: enter falling state
- While airborne: reduce horizontal input by AirControlFactor

- [ ] **Step 4: Write failing tests**

```csharp
[Fact] Update_JumpOnFlatTerrain_BecomesAirborne()
[Fact] Update_AirborneFrame_ZIncreasesThenDecreases()
[Fact] Update_Landing_ReturnsToGround()
[Fact] Update_WalkOffLedge_BecomesFalling()
```

- [ ] **Step 5: Wire Space key in GameWindow**

In the player-mode OnUpdate block, add `Jump: kb.IsKeyPressed(Key.Space)` to the MovementInput constructor.

- [ ] **Step 6: Run tests, commit**

```bash
git commit -m "feat(app+core): Phase B.3 — jump with momentum-preserving gravity arc"
```

---

## Task 5: Portal space state machine

**Files:**
- Modify: `src/AcDream.Core.Net/WorldSession.cs`
- Modify: `src/AcDream.App/Rendering/GameWindow.cs`
- Modify: `src/AcDream.App/Input/PlayerMovementController.cs`

- [ ] **Step 1: Add PlayerTeleport handler to WorldSession**

In `ProcessDatagram`, add a handler for the PlayerTeleport opcode. Check holtburger for the exact opcode — it may be a GameEvent (0xF7B0) with inner type. Add a `TeleportStarted` event on WorldSession.

- [ ] **Step 2: Add PlayerState enum to PlayerMovementController**

```csharp
public enum PlayerState { InWorld, PortalSpace }
public PlayerState State { get; private set; } = PlayerState.InWorld;
```

In `Update`: if State == PortalSpace, return immediately (no movement processed).

- [ ] **Step 3: Wire in GameWindow**

Subscribe to `TeleportStarted` → set controller State to PortalSpace.
In `OnLivePositionUpdated`: if currently in PortalSpace and position changed significantly, recenter streaming, snap position, set State to InWorld, send LoginComplete.

Reset `_loginCompleteSent` latch to allow re-sending after teleport.

- [ ] **Step 4: Run tests, commit**

```bash
git commit -m "feat(net+app): Phase B.3 — portal-space state machine for teleports"
```

---

## Task 6: Setup.StepUpHeight + scenery road fix

**Files:**
- Modify: `src/AcDream.App/Rendering/GameWindow.cs`
- Modify: `src/AcDream.Core/World/SceneryGenerator.cs`
- Test: `tests/AcDream.Core.Tests/World/SceneryGeneratorTests.cs` (new)

- [ ] **Step 1: Read Setup.StepUpHeight when entering player mode**

In the Tab handler, after loading the Setup, set:
```csharp
_playerController.StepUpHeight = setup.StepUpHeight > 0f ? setup.StepUpHeight : 2f;
```

- [ ] **Step 2: Add road exclusion to SceneryGenerator**

In `SceneryGenerator.Generate`, after extracting `terrainType` at line 68, add a check to skip road terrain types. The exact road value needs verification from the dat — check `Region.TerrainInfo.TerrainTypes` for which indices are roads, or check if the raw terrain value has a road bit.

Read `references/ACViewer/` or `references/WorldBuilder/` for how they detect road terrain. The simplest approach: check `terrainType` against known road indices from the Region dat.

- [ ] **Step 3: Write a scenery road exclusion test**

Create `tests/AcDream.Core.Tests/World/SceneryGeneratorTests.cs` with a test that verifies no scenery is generated at a road vertex.

- [ ] **Step 4: Run all tests, commit**

```bash
git commit -m "fix(app+core): Phase B.3 — Setup.StepUpHeight + scenery road exclusion"
```

---

## Task 7: Visual verification + roadmap update

- [ ] **Step 1: Live verification**

Launch the app, log in, press Tab, and verify all 12 acceptance criteria from the spec:
1. Walk outdoors ✓ (already works)
2. Walk to next landblock
3. Walk into a building through a door
4. Walk inside a building
5. Walk back out
6. Walk between rooms
7. Jump while walking
8. Jump off a ledge
9. Enter a portal → arrive at destination
10. Step-height feels right
11. No trees on roads
12. ACE console clean

- [ ] **Step 2: Update roadmap**

Mark B.3 Complete as shipped in `docs/plans/2026-04-11-roadmap.md`.

- [ ] **Step 3: Commit**

```bash
git commit -m "docs: mark Phase B.3 Complete (movement + world navigation) as shipped"
```

---

## Self-review

**Spec coverage:**
- CellPortal indoor transitions (outdoor→indoor, indoor→indoor, indoor→outdoor) → Tasks 1, 2, 3 ✓
- Multi-landblock boundary crossing → Task 2 (test) ✓
- Jump + gravity + falling → Task 4 ✓
- Portal space state machine → Task 5 ✓
- Setup.StepUpHeight → Task 6 ✓
- Scenery road fix → Task 6 ✓
- All 12 acceptance criteria → Task 7 ✓

**Placeholder scan:** Tasks 2 and 3 have "read the reference code" instructions instead of exact code — this is intentional because the portal-plane crossing logic depends on ACViewer's exact convention for PortalFlags.PortalSide and polygon winding, which must be verified at implementation time. The subagent is instructed to read specific reference files.

**Type consistency:** `PortalPlane` record used in Tasks 1, 2, 3. `PlayerState` enum in Task 5. `MovementInput.Jump` in Task 4. All consistent.