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refactor(A.5 T9): _surfaceCache -> ConcurrentDictionary for off-thread mesh build

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Widens LandblockMesh.Build's surfaceCache parameter from Dictionary to
IDictionary so any IDictionary implementation compiles at call sites.
Switches GameWindow._surfaceCache from Dictionary to ConcurrentDictionary
so T11's streaming worker can call Build off the render thread without
a lock.

The TryGetValue+assign lookup inside Build is not atomic, but BuildSurface
is deterministic (same palCode -> same SurfaceInfo), making last-write-wins
under concurrent access benign. Comment added at the pattern site.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
This commit is contained in:
Erik 2026-05-09 22:55:53 +02:00
parent a0741bd13a
commit 4be392b361
2 changed files with 9 additions and 3 deletions
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6
src/AcDream.App/Rendering/GameWindow.cs
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@ -111,7 +111,9 @@ public sealed class GameWindow : IDisposable
// LandblockMesh.Build without re-deriving these each time.
private float[]? _heightTable;
private AcDream.Core.Terrain.TerrainBlendingContext? _blendCtx;
private Dictionary<uint, AcDream.Core.Terrain.SurfaceInfo>? _surfaceCache;
// Was: Dictionary<uint, SurfaceInfo>. ConcurrentDictionary so the off-thread
// mesh builder (A.5 T11+) can call LandblockMesh.Build without a lock.
private System.Collections.Concurrent.ConcurrentDictionary<uint, AcDream.Core.Terrain.SurfaceInfo>? _surfaceCache;
// Phase A.1 Task 8: worker thread pre-builds EnvCell room-mesh sub-meshes
// (CPU only) and stores them here. ApplyLoadedTerrain (render thread) drains
@ -1465,7 +1467,7 @@ public sealed class GameWindow : IDisposable
RoadAlphaRCodes: terrainAtlas.RoadAlphaRCodes);
_heightTable = heightTable;
_surfaceCache = new Dictionary<uint, AcDream.Core.Terrain.SurfaceInfo>();
_surfaceCache = new System.Collections.Concurrent.ConcurrentDictionary<uint, AcDream.Core.Terrain.SurfaceInfo>();
// (Bindless detection moved above — must precede TerrainAtlas.Build /
// TerrainModernRenderer ctor so they can consume BindlessSupport.)

6
src/AcDream.Core/Terrain/LandblockMesh.cs
View file

@ -46,7 +46,7 @@ public static class LandblockMesh
uint landblockY,
float[] heightTable,
TerrainBlendingContext ctx,
Dictionary<uint, SurfaceInfo> surfaceCache)
System.Collections.Generic.IDictionary<uint, SurfaceInfo> surfaceCache)
{
ArgumentNullException.ThrowIfNull(block);
ArgumentNullException.ThrowIfNull(heightTable);
@ -105,6 +105,10 @@ public static class LandblockMesh
uint palCode = TerrainBlending.GetPalCode(
rBL, rBR, rTR, rTL, ttBL, ttBR, ttTR, ttTL);
// Lookup-or-build pattern. Not atomic under concurrent access
// (TryGetValue then assign), but BuildSurface is deterministic —
// two workers building the same palCode produce equal SurfaceInfo,
// last-write-wins is benign.
if (!surfaceCache.TryGetValue(palCode, out var surf))
{
surf = TerrainBlending.BuildSurface(palCode, ctx);