fix(render): A7 Fix D D-2 — EnvCell shell binds its own per-cell light set (#140)

The cell shell read whatever light set (SSBO 4/5) WbDrawDispatcher last left
bound, lighting walls with a leaked set. EnvCellRenderer now uploads its own
binding=4 global lights (frame PointSnapshot via GlobalLightPacker) + a binding=5
per-instance set, computed per cell by LightManager.SelectForObject over the
cell's world bounds (mirrors _cellIdToSlot + WbDrawDispatcher.ComputeEntityLightSet).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/AcDream.App/Rendering/GameWindow.cs

@@ -7775,6 +7775,7 @@ public sealed class GameWindow : IDisposable
             // SceneLighting UBO built below (binding=1) — terrain/sky read those.
             Lighting.BuildPointLightSnapshot(camPos);
             _wbDrawDispatcher?.SetSceneLights(Lighting.PointSnapshot);
+            _envCellRenderer?.SetPointSnapshot(Lighting.PointSnapshot);   // A7 Fix D (D-2)
 
             var ubo = AcDream.Core.Lighting.SceneLightingUbo.Build(
                 Lighting, in atmo, camPos, (float)WorldTime.DayFraction);

src/AcDream.App/Rendering/Wb/EnvCellRenderer.cs

@@ -88,6 +88,17 @@ public sealed unsafe class EnvCellRenderer : IDisposable
     private uint _clipSlotBuffer;
     private uint[] _clipSlotData = Array.Empty<uint>();
 
+    // A7 Fix D (D-2): this renderer owns its lighting (self-contained GL state,
+    // like uViewProjection) instead of reading the SSBO 4/5 WbDrawDispatcher last
+    // left bound. binding=4 = global point-light snapshot (same data/indices as the
+    // dispatcher, via GlobalLightPacker); binding=5 = 8 int indices per instance.
+    private uint _globalLightsSsbo;                       // binding=4
+    private float[] _globalLightData = new float[AcDream.Core.Lighting.GlobalLightPacker.FloatsPerLight * 16];
+    private uint _instLightSetSsbo;                       // binding=5
+    private int[] _lightSetData = new int[1024 * AcDream.Core.Lighting.LightManager.MaxLightsPerObject];
+    private System.Collections.Generic.IReadOnlyList<AcDream.Core.Lighting.LightSource>? _pointSnapshot;
+    private readonly System.Collections.Generic.Dictionary<uint, int[]> _cellLightSetCache = new();
+
     // Phase U.3: SHARED per-cell clip-region SSBO (binding=2) handed in via
     // SetClipRegionSsbo (the GameWindow-level ClipFrame buffer). When 0, we bind
     // our own one-slot no-clip fallback so the shader never reads an unbound SSBO.
@@ -231,6 +242,18 @@ public sealed unsafe class EnvCellRenderer : IDisposable
         _gl.BufferData(GLEnum.ShaderStorageBuffer,
             (nuint)(_modernInstanceCapacity * sizeof(uint)), null, GLEnum.DynamicDraw);
 
+        // A7 Fix D (D-2): binding=4 global lights + binding=5 per-instance light set.
+        _gl.GenBuffers(1, out _globalLightsSsbo);
+        _gl.BindBuffer(GLEnum.ShaderStorageBuffer, _globalLightsSsbo);
+        _gl.BufferData(GLEnum.ShaderStorageBuffer,
+            (nuint)(_globalLightData.Length * sizeof(float)), null, GLEnum.DynamicDraw);
+
+        _gl.GenBuffers(1, out _instLightSetSsbo);
+        _gl.BindBuffer(GLEnum.ShaderStorageBuffer, _instLightSetSsbo);
+        _gl.BufferData(GLEnum.ShaderStorageBuffer,
+            (nuint)(_modernInstanceCapacity * AcDream.Core.Lighting.LightManager.MaxLightsPerObject * sizeof(int)),
+            null, GLEnum.DynamicDraw);
+
         _gl.BindBuffer(GLEnum.ShaderStorageBuffer, 0);
         _gl.BindBuffer(GLEnum.DrawIndirectBuffer, 0);
     }
@@ -262,6 +285,17 @@ public sealed unsafe class EnvCellRenderer : IDisposable
     public void SetClipRouting(IReadOnlyDictionary<uint, int>? cellIdToSlot)
         => _cellIdToSlot = cellIdToSlot;
 
+    /// <summary>
+    /// A7 Fix D (D-2): hand the renderer this frame's point-light snapshot
+    /// (LightManager.PointSnapshot). Call once per frame BEFORE Render, alongside
+    /// the WbDrawDispatcher snapshot wire-in. Indices in the per-cell light sets
+    /// reference this snapshot, which is also uploaded to binding=4 here, so the
+    /// pass is self-contained. Null/empty -> shells receive no point lights.
+    /// </summary>
+    public void SetPointSnapshot(
+        System.Collections.Generic.IReadOnlyList<AcDream.Core.Lighting.LightSource>? snapshot)
+        => _pointSnapshot = snapshot;
+
     // ---------------------------------------------------------------------------
     // GetEnvCellGeomId
     // Verbatim copy of WB EnvCellRenderManager.cs:94-103.
@@ -997,6 +1031,35 @@ public sealed unsafe class EnvCellRenderer : IDisposable
         }
     }
 
+    // ---------------------------------------------------------------------------
+    // GetCellLightSet (A7 Fix D D-2 helper)
+    // Per-cell up-to-8 point lights, cached per frame. Camera-independent, like
+    // WbDrawDispatcher.ComputeEntityLightSet — keyed on the cell's world bounds.
+    // ---------------------------------------------------------------------------
+
+    // A7 Fix D (D-2): the up-to-8 point lights reaching a cell, by the cell's world
+    // bounding sphere (camera-independent, like WbDrawDispatcher.ComputeEntityLightSet).
+    // Cached per frame; unused slots are -1 (shader adds no point light there).
+    private int[] GetCellLightSet(uint cellId)
+    {
+        if (_cellLightSetCache.TryGetValue(cellId, out var cached)) return cached;
+
+        var set = new int[AcDream.Core.Lighting.LightManager.MaxLightsPerObject];
+        System.Array.Fill(set, -1);
+
+        var snap = _pointSnapshot;
+        if (snap is { Count: > 0 } &&
+            _landblocks.TryGetValue(cellId & 0xFFFF0000u, out var lb) &&
+            lb.EnvCellBounds.TryGetValue(cellId, out var b))
+        {
+            Vector3 center = (b.Min + b.Max) * 0.5f;
+            float radius = (b.Max - b.Min).Length() * 0.5f;
+            AcDream.Core.Lighting.LightManager.SelectForObject(snap, center, radius, set);
+        }
+        _cellLightSetCache[cellId] = set;
+        return set;
+    }
+
     // ---------------------------------------------------------------------------
     // RenderModernMDIInternal
     // Extracted from WB BaseObjectRenderManager.cs:709-848 (single-slot variant).
@@ -1016,6 +1079,15 @@ public sealed unsafe class EnvCellRenderer : IDisposable
         int passIdx = (int)renderPass;
         if (passIdx < 0 || passIdx > 2) return;
 
+        // A7 Fix D (D-2): per-frame per-cell light-set cache (built lazily in
+        // GetCellLightSet below). Clear once here so each cell gets a fresh lookup
+        // using this frame's _pointSnapshot. Called for EVERY pass (opaque AND
+        // transparent); the cache entries are stable within a frame since PointSnapshot
+        // doesn't change between Render calls, so clearing once (at the opaque pass)
+        // and leaving stale entries for the transparent pass would also be correct, but
+        // clearing both is safe and matches WbDrawDispatcher's per-call ComputeEntityLightSet.
+        _cellLightSetCache.Clear();
+
         // §4 outdoor full-world flap (2026-06-10): hoisted from below the SSBO uploads.
         // Without the global VAO nothing can draw, and returning AFTER the pass state
         // was established leaked it (same early-out shape as the totalDraws==0 leak —
@@ -1213,6 +1285,35 @@ public sealed unsafe class EnvCellRenderer : IDisposable
                 (nuint)(uniqueInstanceCount * sizeof(uint)), ptr);
         }
 
+        // A7 Fix D (D-2): per-instance 8-int light set, parallel to the transforms,
+        // keyed on the cell each shell instance belongs to (mirrors _clipSlotData).
+        int lightStride = AcDream.Core.Lighting.LightManager.MaxLightsPerObject;
+        if (_lightSetData.Length < uniqueInstanceCount * lightStride)
+            _lightSetData = new int[System.Math.Max(_lightSetData.Length * 2, uniqueInstanceCount * lightStride)];
+        for (int i = 0; i < uniqueInstanceCount; i++)
+        {
+            int[] cellSet = GetCellLightSet(allInstances[i].CellId);
+            System.Array.Copy(cellSet, 0, _lightSetData, i * lightStride, lightStride);
+        }
+
+        // A7 Fix D (D-2): upload binding=4 (global lights) + binding=5 (per-instance set).
+        int lightCount = AcDream.Core.Lighting.GlobalLightPacker.Pack(_pointSnapshot, ref _globalLightData);
+        int glUploadCount = lightCount > 0 ? lightCount : 1;
+        _gl.BindBuffer(GLEnum.ShaderStorageBuffer, _globalLightsSsbo);
+        _gl.BufferData(GLEnum.ShaderStorageBuffer,
+            (nuint)(glUploadCount * AcDream.Core.Lighting.GlobalLightPacker.FloatsPerLight * sizeof(float)),
+            null, GLEnum.DynamicDraw);
+        fixed (float* gp = _globalLightData)
+            _gl.BufferSubData(GLEnum.ShaderStorageBuffer, 0,
+                (nuint)(glUploadCount * AcDream.Core.Lighting.GlobalLightPacker.FloatsPerLight * sizeof(float)), gp);
+
+        _gl.BindBuffer(GLEnum.ShaderStorageBuffer, _instLightSetSsbo);
+        _gl.BufferData(GLEnum.ShaderStorageBuffer,
+            (nuint)(uniqueInstanceCount * lightStride * sizeof(int)), null, GLEnum.DynamicDraw);
+        fixed (int* lp = _lightSetData)
+            _gl.BufferSubData(GLEnum.ShaderStorageBuffer, 0,
+                (nuint)(uniqueInstanceCount * lightStride * sizeof(int)), lp);
+
         // WB BaseObjectRenderManager.cs:807-818: bind VAO + SSBOs + barrier.
         // (globalVao validated at the top of the method — a return here would leak the
         // pass state established above.)
@@ -1228,6 +1329,8 @@ public sealed unsafe class EnvCellRenderer : IDisposable
         // (binding=2, via the GameWindow ClipFrame or our no-clip fallback).
         _gl.BindBufferBase(GLEnum.ShaderStorageBuffer, 3, _clipSlotBuffer);
         BindClipRegionBinding2();
+        _gl.BindBufferBase(GLEnum.ShaderStorageBuffer, 4, _globalLightsSsbo);   // A7 Fix D (D-2)
+        _gl.BindBufferBase(GLEnum.ShaderStorageBuffer, 5, _instLightSetSsbo);   // A7 Fix D (D-2)
         _gl.BindBuffer(GLEnum.DrawIndirectBuffer, _mdiCommandBuffer);
 
         _gl.MemoryBarrier(MemoryBarrierMask.ShaderStorageBarrierBit | MemoryBarrierMask.CommandBarrierBit);
@@ -1443,5 +1546,7 @@ public sealed unsafe class EnvCellRenderer : IDisposable
         if (_modernBatchBuffer != 0)   { _gl.DeleteBuffer(_modernBatchBuffer);    _modernBatchBuffer   = 0; }
         if (_clipSlotBuffer != 0)      { _gl.DeleteBuffer(_clipSlotBuffer);       _clipSlotBuffer      = 0; } // Phase U.3
         if (_fallbackClipRegionSsbo != 0) { _gl.DeleteBuffer(_fallbackClipRegionSsbo); _fallbackClipRegionSsbo = 0; } // Phase U.3
+        if (_globalLightsSsbo != 0)   { _gl.DeleteBuffer(_globalLightsSsbo);    _globalLightsSsbo    = 0; } // A7 Fix D (D-2)
+        if (_instLightSetSsbo != 0)   { _gl.DeleteBuffer(_instLightSetSsbo);    _instLightSetSsbo    = 0; } // A7 Fix D (D-2)
     }
 }