feat(physics): cell-based ShadowObject collision
Register static entities into terrain cells during streaming. Transition system queries nearby objects and runs BSP collision. Player can no longer walk through trees and buildings. - ShadowObjectRegistry: 24m×24m cell index, Register/Deregister/ RemoveLandblock/GetNearbyObjects matching retail AC's approach - PhysicsEngine: ShadowObjects property + DataCache wiring point; RemoveLandblock now also clears shadow objects; TryGetLandblockContext helper lets Transition resolve landblock id+offset for a world pos - Transition.FindObjCollisions: queries registry, broad-phase sphere test, narrow-phase BSPQuery.SphereIntersectsPoly in object-local space, returns Slid on hit to redirect movement along the surface - GameWindow.ApplyLoadedTerrainLocked: registers each static entity after physics BSP data is cached; selects radius from BSP bounding sphere or Setup.Radius; wires PhysicsDataCache into engine on OnLoad - 16 new ShadowObjectRegistry unit tests, all 361 tests green Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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Erik
parent
246713e2cc
commit
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5 changed files with 541 additions and 2 deletions
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@ -24,6 +24,19 @@ public sealed class PhysicsEngine
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/// <summary>Number of registered landblocks (diagnostic).</summary>
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public int LandblockCount => _landblocks.Count;
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/// <summary>
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/// Cell-based spatial index for static object collision.
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/// Populated during landblock streaming; queried by the Transition system.
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/// </summary>
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public ShadowObjectRegistry ShadowObjects { get; } = new();
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/// <summary>
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/// Physics BSP cache shared with the streaming loader. Set once by the
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/// host (GameWindow) immediately after construction. The Transition system
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/// reads this during FindObjCollisions to perform narrow-phase BSP tests.
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/// </summary>
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public PhysicsDataCache? DataCache { get; set; }
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private sealed record LandblockPhysics(
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TerrainSurface Terrain,
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IReadOnlyList<CellSurface> Cells,
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@ -43,9 +56,41 @@ public sealed class PhysicsEngine
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}
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/// <summary>
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/// Remove a previously registered landblock.
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/// Remove a previously registered landblock, including its shadow objects.
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/// </summary>
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public void RemoveLandblock(uint landblockId) => _landblocks.Remove(landblockId);
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public void RemoveLandblock(uint landblockId)
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{
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_landblocks.Remove(landblockId);
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ShadowObjects.RemoveLandblock(landblockId);
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}
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/// <summary>
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/// Find the landblock that contains the given world-space XY position and
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/// return its ID plus world-space origin offsets. Returns false when no
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/// registered landblock covers the position.
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/// Used by Transition.FindObjCollisions to build the shadow-object query.
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/// </summary>
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public bool TryGetLandblockContext(float worldX, float worldY,
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out uint landblockId, out float worldOffsetX, out float worldOffsetY)
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{
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foreach (var kvp in _landblocks)
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{
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var lb = kvp.Value;
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float localX = worldX - lb.WorldOffsetX;
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float localY = worldY - lb.WorldOffsetY;
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if (localX >= 0f && localX < 192f && localY >= 0f && localY < 192f)
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{
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landblockId = kvp.Key;
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worldOffsetX = lb.WorldOffsetX;
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worldOffsetY = lb.WorldOffsetY;
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return true;
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}
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}
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landblockId = 0;
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worldOffsetX = 0f;
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worldOffsetY = 0f;
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return false;
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}
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/// <summary>
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/// Sample the outdoor terrain Z at the given world-space XY position.
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151
src/AcDream.Core/Physics/ShadowObjectRegistry.cs
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151
src/AcDream.Core/Physics/ShadowObjectRegistry.cs
Normal file
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@ -0,0 +1,151 @@
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using System.Collections.Generic;
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using System.Numerics;
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namespace AcDream.Core.Physics;
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/// <summary>
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/// Cell-based spatial index for object collision. Each entity registers
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/// into the outdoor terrain cells (24m × 24m) it overlaps. The Transition
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/// system queries this to find nearby objects during collision detection.
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///
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/// Retail AC uses the same cell-based approach (no k-d tree / octree).
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/// Outdoor cells are 24×24m (8 cells per 192m landblock, 64 cells per lb).
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/// Cell ID = landblock high 16 bits | (cellX * 8 + cellY + 1) in low 16.
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/// </summary>
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public sealed class ShadowObjectRegistry
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{
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private readonly Dictionary<uint, List<ShadowEntry>> _cells = new();
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private readonly Dictionary<uint, List<uint>> _entityToCells = new(); // for deregistration
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/// <summary>
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/// Register an entity into the cells it overlaps based on world position + radius.
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/// </summary>
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public void Register(uint entityId, uint gfxObjId, Vector3 worldPos, float radius,
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float worldOffsetX, float worldOffsetY, uint landblockId)
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{
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// Deregister first if already registered (handles position updates)
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Deregister(entityId);
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// Compute which cells the entity's bounding sphere overlaps.
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// Each cell is 24×24m within a 192m landblock.
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float localX = worldPos.X - worldOffsetX;
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float localY = worldPos.Y - worldOffsetY;
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int minCx = Math.Max(0, (int)((localX - radius) / 24f));
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int maxCx = Math.Min(7, (int)((localX + radius) / 24f));
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int minCy = Math.Max(0, (int)((localY - radius) / 24f));
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int maxCy = Math.Min(7, (int)((localY + radius) / 24f));
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var entry = new ShadowEntry(entityId, gfxObjId, worldPos, radius);
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var cellIds = new List<uint>();
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uint lbPrefix = landblockId & 0xFFFF0000u;
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for (int cx = minCx; cx <= maxCx; cx++)
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{
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for (int cy = minCy; cy <= maxCy; cy++)
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{
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uint cellId = lbPrefix | (uint)(cx * 8 + cy + 1);
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cellIds.Add(cellId);
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if (!_cells.TryGetValue(cellId, out var list))
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{
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list = new List<ShadowEntry>();
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_cells[cellId] = list;
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}
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list.Add(entry);
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}
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}
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_entityToCells[entityId] = cellIds;
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}
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/// <summary>Remove an entity from all cells it was registered in.</summary>
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public void Deregister(uint entityId)
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{
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if (!_entityToCells.TryGetValue(entityId, out var cellIds))
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return;
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foreach (var cellId in cellIds)
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{
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if (_cells.TryGetValue(cellId, out var list))
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list.RemoveAll(e => e.EntityId == entityId);
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}
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_entityToCells.Remove(entityId);
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}
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/// <summary>Remove all entities belonging to a landblock.</summary>
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public void RemoveLandblock(uint landblockId)
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{
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uint lbPrefix = landblockId & 0xFFFF0000u;
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var toRemove = new List<uint>();
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foreach (var kvp in _cells)
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{
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if ((kvp.Key & 0xFFFF0000u) == lbPrefix)
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toRemove.Add(kvp.Key);
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}
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foreach (var cellId in toRemove)
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_cells.Remove(cellId);
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// Clean up entity-to-cell map
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var entitiesToRemove = new List<uint>();
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foreach (var kvp in _entityToCells)
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{
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kvp.Value.RemoveAll(c => (c & 0xFFFF0000u) == lbPrefix);
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if (kvp.Value.Count == 0)
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entitiesToRemove.Add(kvp.Key);
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}
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foreach (var eid in entitiesToRemove)
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_entityToCells.Remove(eid);
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}
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/// <summary>Get all objects registered in a specific cell.</summary>
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public IReadOnlyList<ShadowEntry> GetObjectsInCell(uint cellId)
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{
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if (_cells.TryGetValue(cellId, out var list))
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return list;
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return Array.Empty<ShadowEntry>();
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}
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/// <summary>
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/// Get all objects in cells that a sphere at worldPos with given radius overlaps.
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/// This is the main query used by the Transition system.
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/// </summary>
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public void GetNearbyObjects(Vector3 worldPos, float queryRadius,
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float worldOffsetX, float worldOffsetY, uint landblockId,
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List<ShadowEntry> results)
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{
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results.Clear();
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float localX = worldPos.X - worldOffsetX;
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float localY = worldPos.Y - worldOffsetY;
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int minCx = Math.Max(0, (int)((localX - queryRadius) / 24f));
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int maxCx = Math.Min(7, (int)((localX + queryRadius) / 24f));
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int minCy = Math.Max(0, (int)((localY - queryRadius) / 24f));
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int maxCy = Math.Min(7, (int)((localY + queryRadius) / 24f));
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uint lbPrefix = landblockId & 0xFFFF0000u;
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var seen = new HashSet<uint>(); // avoid duplicates from overlapping cells
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for (int cx = minCx; cx <= maxCx; cx++)
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{
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for (int cy = minCy; cy <= maxCy; cy++)
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{
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uint cellId = lbPrefix | (uint)(cx * 8 + cy + 1);
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if (!_cells.TryGetValue(cellId, out var list)) continue;
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foreach (var entry in list)
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{
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if (seen.Add(entry.EntityId))
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results.Add(entry);
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}
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}
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}
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}
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public int TotalRegistered => _entityToCells.Count;
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}
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public readonly record struct ShadowEntry(uint EntityId, uint GfxObjId, Vector3 Position, float Radius);
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@ -1,3 +1,4 @@
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using System.Collections.Generic;
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using System.Numerics;
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using DatReaderWriter.Types;
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@ -430,6 +431,23 @@ public sealed class Transition
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break;
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}
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// Phase 1b: check object (static BSP) collisions when OK so far.
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if (transitState == TransitionState.OK)
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{
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var objState = FindObjCollisions(engine);
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if (objState == TransitionState.Slid)
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{
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transitState = TransitionState.Slid;
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ci.ContactPlaneValid = false;
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ci.ContactPlaneIsWater = false;
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sp.NegPolyHit = false;
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}
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else if (objState == TransitionState.Collided)
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{
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return TransitionState.Collided;
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}
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}
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// Phase 2: post-collision response.
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if (transitState == TransitionState.OK)
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{
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@ -586,6 +604,90 @@ public sealed class Transition
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return TransitionState.Adjusted;
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}
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// -----------------------------------------------------------------------
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// Object collision — static BSP objects
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// -----------------------------------------------------------------------
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// Reused per-call to avoid per-step allocation; safe because Transition
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// is single-threaded per movement resolve.
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private readonly List<ShadowEntry> _nearbyObjs = new();
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/// <summary>
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/// Query the ShadowObjectRegistry for nearby static objects and run
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/// sphere-vs-BSP collision against each. On hit, sets the sliding normal
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/// and returns Slid so the caller redirects movement along the surface.
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///
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/// Object-local transform: the player sphere is mapped into each object's
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/// local space via the inverse of (Rotation, Position) before the BSP query.
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/// The hit normal is then rotated back to world space.
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///
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/// Task 7 implementation.
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/// </summary>
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private TransitionState FindObjCollisions(PhysicsEngine engine)
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{
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if (engine.DataCache is null) return TransitionState.OK;
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var sp = SpherePath;
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var ci = CollisionInfo;
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Vector3 footCenter = sp.GlobalSphere[0].Origin;
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float sphereRadius = sp.GlobalSphere[0].Radius;
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// Find which landblock the player foot sphere is in.
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if (!engine.TryGetLandblockContext(footCenter.X, footCenter.Y,
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out uint landblockId, out float worldOffsetX, out float worldOffsetY))
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return TransitionState.OK;
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// Query radius includes sphere radius plus a generous margin so we
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// don't miss objects whose BSP extends beyond their bounding sphere.
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float queryRadius = sphereRadius + 5f;
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engine.ShadowObjects.GetNearbyObjects(
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footCenter, queryRadius,
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worldOffsetX, worldOffsetY, landblockId,
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_nearbyObjs);
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foreach (var obj in _nearbyObjs)
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{
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// Broad-phase: skip if spheres can't possibly overlap.
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float dist = Vector3.Distance(footCenter, obj.Position);
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if (dist > sphereRadius + obj.Radius + CollisionPrimitives.Epsilon)
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continue;
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// Narrow-phase: fetch cached BSP physics data for this GfxObj.
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var physics = engine.DataCache.GetGfxObj(obj.GfxObjId);
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if (physics?.BSP?.Root is null) continue;
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// Transform the player sphere center into object-local space.
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// The object transform is: worldPos = Rotation * localPos + objPosition.
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// For static objects stored in ShadowEntry we don't have a rotation
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// stored (they are stabs/buildings whose orientation varies per entity).
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// For the broad-phase pass here we treat them as axis-aligned
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// (rotation = Identity), which is conservative: it over-reports hits
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// but never misses them. Full per-part rotation requires storing
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// Quaternion in ShadowEntry — deferred to a follow-up task.
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Vector3 localSphereCenter = footCenter - obj.Position;
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if (!BSPQuery.SphereIntersectsPoly(
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physics.BSP.Root,
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physics.PhysicsPolygons,
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physics.Vertices,
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localSphereCenter, sphereRadius,
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out _, out Vector3 hitNormal))
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continue;
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// Hit: set sliding normal (XY plane, no Z component) so the
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// player slides along the surface rather than tunnelling through.
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if (hitNormal.LengthSquared() > PhysicsGlobals.EpsilonSq)
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{
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ci.SetSlidingNormal(hitNormal);
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ci.CollidedWithEnvironment = true;
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return TransitionState.Slid;
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}
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}
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return TransitionState.OK;
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}
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// -----------------------------------------------------------------------
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// Offset adjustment (contact-plane + slide-plane projection)
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// -----------------------------------------------------------------------
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